June 2026

The long Spring drought broke on the evening of the first day of meteorological summer and we had 2.5cm of rain over 24 hours. 

May 2026

I did the bird count on the 5th. This confirmed that there was just the one Mute Swan on the lake. I guess that the pen and her brood were got by a fox? By the end of the month, there were a pair of swans again, so the Cob had obtained a replacement mate. Sometimes the Swan Sanctuary carries out a rescue, but I haven't heard of any recent activity there. Meanwhile, the geese all managed to hatch broods. There were three pairs of Greylags accompanying their broods, two sets of Egyptians and one Canada Goose brood. Just the one Great-crested Grebe was seen, the hope is that the other was sitting tight on a nest. Swifts were evident most days in the month, commuting to the lake, so there must be some insects emerging to make those commutes worthwhile. Swarms of non-biting midges were noted on the 30th. Blackbirds, Robins, Song Thrushes, Stock Doves, Woodpigeons and Wrens were all singing, in most cases in the lead up to a second brood, I expect. Some birds were conspicuous commuting between feeding places and their nests, with Starlings most obvious.

Hawthorns were in bloom early in the month. 

At the beginning of the month, the effects of widespread spraying with glyphosate became evident. Despite the acknowledged value of Admiral's Hedge, this herbicide was sprayed onto hedge-bottom plants, so killing off everything growing there. Hedge bottom wildflowers are valuable, but here they get no chance. The perimeter path here is separated from the hedge by a grassy strip which is mown regularly. This frequency is appropriate beside the path, but there is room for a natural hedge bottom on the other side here, instead of the scortched earth that we now have. We still don't know why natural vegetation is regarded as the enemy here .

At the same time, elsewhere in the park, spray was used around the base of trees, poles, fences, hedges and seats. I had planted out some woodland wildflowers in Cecile's hedge, hoping to establish them in the park. Unfortunately I put them near the seats, so that I knew where to look to see if they established. Sadly, almost all of them were sprayed out. Here, too, there was no need for glyphosate use, as the hedge bottom plants there were shaded by the shrubs of the hedge and so were not tall or invasive at all. 

Glyphosate is licensed for use in England, but I don't imagine parents and carers will be delighted to have their little ones investigating the bottom of the fences beside the children's play areas. Children investigate things in their natural exploratory behaviour and the chemical can take hours to be absorbed when humidity is high. It's my view that there are easy alternatives in most or all of the places that glyphosate is used. One can decide to live with, and celebrate, the wildflowers, or use a strimmer.

Painted Lady

The warm dry Spring resulted in a surge in insect populations. Late in the month I saw several Painted Lady butterflies. This species is a migrant from the Mediterranean, numbers varying between years. A conspicuous resident species was the Broad-bodied Chaser dragonfly, which I saw dipping to the surface of the lake depositing eggs. There were also many Large Red Damselflies and one of the many blue damselfly species.

Broad-bodied Chaser

 

 

The vegetation of Ricardo's Shrubbery is now dense, making it difficult to find all the species, but a survey added 10 extras and corrections to some previous identifications.

At this time of year the hedgerows and woodland edges need pruning to remove vigorous incursions into the adjacent grassland whilst retaining the flowering and fruiting branches. I did this with hand tools, as the bird breeding season has two months to run and nests are notoriously difficult to find in amongst the dense vegetation. Working by hand means that almost all nests can be seen and avoided. 

I sampled the lake water on the 27th. The chemical analysis gave low concentrations of both Phosphates and Nitrates, but the water quality was low nevertheless. The good news is that the benthic blue-green Oscillatoria had diminished, although the bottom sediment remained anoxic and most unpleasant, there were no longer globs rising to the surface with trapped photosynthetic oxygen. The bad news is that there had been an earlier than usual great growth of Aphanizomenon flos-aquae, which floats in mid-water. Roughly one bright-green cluster of filaments per cc of water. The water sports people are aware of this. Most members of the public seem unaware and I see dogs put in to swim and families feeding the birds in big number. The Waterwatch chemical monitoring shows low levels of nitrates and phosphates, perhaps because the blue-greens have taken up most of it. Whilst there is no doubt that the main cause of the blue-green bloom is excess nutrients (exacerbated by the heat wave) I'm not aware that anyone is monitoring the tributaries. That's something that AELTC could afford to do, given that the tributaries all issue from their land. I doubt that the Environment Agency will do anything. There was a big hatch of fish fry on the 27th, probably Carp. Fish-eating birds, however, are in diminished numbers, suggesting that the biomass of small fish remains low.

The Cuckoo Flower Meadow, between the tennis courts and White Pavilion was not living up to its name, with just one or two flowers at the end of the month. Perhaps it should be called Germander Speedwell Meadow, as there was a nice display of this bright blue flower there at the end of the month.

April 2026

I did the monthly bird count on the 4th. There was still quite a lot of singing by resident species, if less than last month and the resident Great Spotted Woodpeckers were silent, presumably busy at the nest. This casts some doubt on the April start for the Birds in Greenspaces scheme, perhaps not optimal for those residents. A Nuthatch was singing in Ashen Grove Wood, so the mismanagement by AELTC must have left some veteran features. The Grey Wagtails were seen on the upper Brook, as usual, and doubtless were breeding somewhere there. The Grebes were still present, so there must have been a few fish to feed upon. I saw three male Pochards on the first of the month, but they were gone on my later visits. The Mute swans are now just the pair, with the Pen sitting on a nest on the Wimbledon Club lake shore. Bare patches in the Great Field had been repaired and there were some 30 Feral pigeons enjoying the free grass seed. Let's hope that the seed isn't chemically treated.

On the 12th I did a bird spotting walk for the national Birds in Greenspaces scheme. A highlight was a sighting of Nuthatch hunting insects on the trunk of a small tree in the public park section of Ashen Grove Wood and watching the Stock Doves and Jackdaws contesting nest sites in the dead veteran Ash tree beside the lake outfall structure. A sad note was a huddled, ill female blackbird, doubtless suffering from the fatal Usutu virus, which is transmitted by Culex mosquitoes. The recent onset of the disease might be symptomatic of climate change causing the invasion of southern species of mosquito, with the accompanying disease risk. Fortunately, Usutu is not known to cause mortality in other other species, or us!

I did the lake water sampling in the 13th, finding that both nitrates and phosphates were then below the pollution threshold. However, the bad news was that the cyanophyte (Blue-green "alga"), Oscillatoria, was abundant across the whole lake bed, combining with the upper layers of sediment to make a slimy goo. Some floated to the top, buoyed up by trapped oxygen, but that was a tiny proportion of the what remained on the bottom. I presume it was the Oscillatoria that had soaked up the nutrient pollutants. We are lucky that it seems not to be toxic (yet), but it leaves the lake water in a dreadful state. There were a few scraps of Rigid Hornwort, a floating waterweed. Lets' hope that it thrives and shades out the cyanophyte. Meanwhile, I look on as dogs are encouraged into the water and children have great fun splashing in their canoes, glad that the precautionary advice to treat the weed as toxic hasn't proved itself. Water clarity remained good, as I could still see my Secchi disk at 1.5m depth off the end of the, now extended, watersports jetty. This would be because there were still plenty of water fleas filter-feeding on the microscopic algae. Over the winter it was mainly the common water flea and the great water flea, but the long-spined flea is now showing up too and a fourth, bottom-dwelling, species.

At the beginning of the month both the Blackthorns and the Hawthorns were beginning to break their leaf buds, but the Blackthorns were in full flower and nothing yet showing on the Hawthorns. The Wild cherries were in flower in Horse Close Wood, so were readily found. They blend in with the surrounding trees once the flowers drop. There is an abundance of flowers on the Green Alkanet, which is all too successful around the edges of the park.

In the Spring large groups of nursery school toddlers are enjoying the park, which is great to see. An array of logs has been moved into the Lofthouse Glade for outdoor classroom seating, used informally by others too. It's great to see Horse Close Wood so used and the wildflowers appreciated. Let's hope that all the activity is naturally-based, we don't enjoy plastic glitter in this natural scene.

December 2025

Coot numbers remained a near record levels in the count on the 28th. This is suggestive of a resurgence of waterweed, the main food of Coots (and Swans). There were also 100 Woodpigeons, a large number for December.

March 2026

On the 8th, I found out why one of last-year's brood of Mute Swans had been lost from the lake. I had assumed that the, now full-sized, youngsters were seen off by the resident Cob as he came into breeding condition.

 

A regular dog-walker had reported, however, that one of the youngsters had been carried off by the Swan Sanctuary because it had been seen in a distressed state out on the lakeside promenade, prevented from returning to the lake by the Cob. That day I watched this happen to a second bird. I was told that the Cob prevented it from returning to the lake and it was threatened by dogs, so she was going to carry it off to be released to the non-breeding flock on the Thames at Barnes. I was concerned at this, as a fit youngster is quite capable of returning to the water and of fending for itself against most dogs, and would make its way off elsewhere when ready. I suggested that if it could not fend for itself, it should be taken into care to return it to strength. It would be at risk released in a weak state into strange surrounds already occupied by large numbers of fit competitors. My suggestions were ignored; the volunteer told me that people were worried for the swan's welfare. Well, so was I! The bird was last seen being carried off to the volunteer's car for this supposed rescue. All last year's youngsters had gone by the 23rd, let's hope most under their own steam, naturally.

In mid month a 45-year-old double-flowered Wild Cherry beside the Watersports building was felled.  

The stump showed clear signs of rot, so its useful life would have been short, even though it presented no real hazard. On the dam downslope just south of the park depot behind the Bowls Pavilion two Silver Birches and an Umineko Cherry were cut back to stumps. The old planting here is beginning to fall apart, but the works sacrificed valuable dead wood habitat in a place little frequented by people.

Another management action, however, seemed rather pointless. In mid month the vegetation growing on the fence in the middle of Ashen Grove Wood was strimmed. This fence is in the middle of this tiny ancient wood and the vegetation removed was wildlife habitat: mainly Ivy, which provides valuable food and nest sites in Spring, and one Elder which would have flowered and fruited, if left. Whilst the harm was little and the place will recover, it's not obvious to me why this needed doing.

There were a few plants of Spring Squill and one of Spring Starflower flowering in the Revelstoke Road Car Park border. Although the Squill is native on western and northern coastal cliffs, both were certainly planted here, but I don't recall anyone declaring they had done this.

Spring Squill

 

Spring Starflower

 

 

 

 

Horse Close Wood path

Later in the month Dave Welch and I added some bark chippings to the main path in Horse Close Wood beside two of the larger English Oaks. The idea was to add cushioning to lessen ground compaction that might harm the roots of those old trees. We used the occasion to narrow the path, leading people away from a close approach to the trees. For this we used heavy branches.

The Blackcap is increasingly overwintering in England, but the first song was heard on the 19th. I did the monthly bird count on the 23rd and was delighted to see the display of a pair of Great Crested Grebes: not only ending their absence since October last year, but a promise of breeding this year. The Black-headed and Common Gulls had all departed this month.

Unimpeded by last-year's young, the Mute Swan Pen was attending a nest on the Wimbledon Club lakeshore on the 23rd, and the Cob patrolling up and down in the nearby lake, seeing off other waterfowl. 

An electricity cable in the Great Field near the SE corner of the athletics was repaired in the middle of the winter rainy period and the trench promptly filled up with water. It was finally dry enough for it to be filled in and grass seed added, so there was a little flock of Feral Pigeons enjoying the seed!

Construction work on the Padel Tennis was under way and so the usual Green Woodpecker in the stadium was out in the Great Field. Sadly, the increased use by people is problematic for species that are sensitive to disturbance. 

Two Greenfinches in Admiral's hedge were the first I've had since March 2024. They have been affected badly by Trichomonas gallinae disease. It's the same story for the Chaffinch, which I haven't seen since April that year. 

The Wood Spruge

I was sorry to see that Ricardo's Shrubbery was given a lollipop-tree prune. This was unnecessary, as I had already taken back all growth that might protrude over the adjacent path. The prune took away much of the wood that would carry flowers and fruit later in the year, so compromising both amenity and wildlife habitat. And this was done on a planted area that was planted in compensation for losses in the ancient Ashen Grove Wood to the south. 

The good news here, however, is that a Wood Spurge I planted last year has survived the winter and was in flower at the end of the month. I planted some more Wood Sedge and a clump of Wood Millet, hoping to aid the compensation. 

The memorial cherry

 

 

 

 

And another bit of good news is that the Cherry planted as a Kendall family memorial earlier in the year has broken bud and seems to be thriving.

 

 

 

 

 

 

November 2025

 The Black Swans left mid month, after a stay of some six weeks.

February 2026

At some expense, I have subscribed to the international Freshwater Watch citizen science programme, as this gives nutrient sampling kit for 12 months. Previously, we used the free Thames River Watch and other one-off citizen science schemes, but this restricted us to their programme for one-off samples, preventing enough sampling for a good overview. The anglers have sampled lake water quality, but somewhat erratically. The kit arrived a bit late and my first sample was made on the 4th, rather than in January, when it theoretically began. The results were interesting, as the phosphate concentration was the highest I have seen in the 30 samples taken since 2017 and well into the range regarded as nutrient pollution. Although sewage or agricultural runoff are the usual causes of high phosphate, in urban areas road runoff can contribute. No regular sampling is undertaken of the tributaries of the lake. In contrast, the nitrate pollution was low and not indicative of pollution, so there seemed to be a source which adds phosphate but not nitrate. Feeding excess bread, or other food, to the birds is ruled out on those grounds, but it's possible that birds feeding on the grassland and returning to the lake to defecate could mimic sewage pollution. We can also rule out atmospheric deposition, as this would bring nitrates, not phosphates. So, we don't know the source of our high phosphate. We should, and it's reprehensible that AELTC, who own land uphill from the lake and have a drain going direct to the lake, don't admit to carrying out any monitoring. Our lake would be in a terrible mess, were it not for the low concentration of nitrogen constituting a limiting nutrient here.

Then, I did the second sample at the end of the month. The results were startlingly different. Whilst nitrates remained low, the phosphates had come right down, suggesting that the high values were from some brief cause, perhaps an otherwise unreported pollution incident or a seasonal factor coming to an end. So the next months' results are eagerly awaited.

This month reflects the end of winter and first signs of spring. The Blackthorn flowers and Hazel catkins were dying back and most Ivy fruit had been consumed, despite low numbers of the Blackbirds that consume most of them. By the end of the month Alders were flowering, Hawthorn buds were bursting and the first few Hawthorn flowers were seen. Weeping willows are the first trees to break bud and there were fresh leaves on them by the end of the month. White Dead-nettle flowers most of the year, but was seen in plenty. Bluebell and Cuckoo Pint leafs were showing.

It seems that there are few small fish to be had in the lake, as there were still no Great Crested Grebes there yet again. 

 

 

October 2025

I was surprised that the two Black Swans remained on the lake all month. Whilst still harassed a bit by the resident Mute Swan cob, they seemed to have reached an understanding. The extra four Mute Swan cygnets that arrived in late September brought the cygnet total to 10, but briefly, as they had dwindled to 7 by mid month and stayed at that number. Cormorant numbers dwindled through the month, suggesting that there were fewer fish to catch. Grey Wagtails have increased in recent years and were seen occasionally in the brook. The monthly bird count was done on the 24th, when there was a record number of Wood Pigeons, 125.

I did the lake water sampling on the 14th when the Aphenozomenon had disappeared, so the risk of a bloom seemed over this year. There was plenty of blanketweed at the bottom of the lake and a more welcome return of the free-floating Rigid Hornwort, although not so abundant as to cause problems for water sports.

By the end of the month leaf fall was in full swing and the park staff were busy keeping paths clear with the leaf blower. The sweet flag around the lake fringe was also yellowing. The bare patches out in the Great Field had around 100 Feral Pigeons and a few Woodpigeons feeding on the grass seed.

 

September 2025

I offered to assist Thames Water with their investigation of the pollution by blue-green bacteria back at the beginning of August, when I reported the incident to their pollution hotline. Then, I also made a request under the Environmental Information Regulations, which require Water Authorities to disclose environmental information that they hold. The regulations encourage authorities to publish their information and to respond to requests for information within 20 working days. After some 30 working days I received a report on 12th September.

The report provides a little extra information beyond what we know already about the incident. Nearly a day after pollution was first spotted where the Wimbledon Park Brook enters the Wandle at Earlsfield, at 15:30 on the 24th July, a water consultancy, Network Service Contractors, confirmed the blue discolouration of the brook there. At 17:15 another consultancy, OHES, arrived there to carry out water quality measurements. Fearing that the pollution might damage their equipment, OHES took bottle samples of the water. This was about a day after the discolouration was first observed and some 8 hours after it was reported. They saw no fish, alive or dead and no visual evidence of sewage pollution. At 19:00 at Network Engineer (presumably from Thames Water) arrived to determine that there was 1 ppm of ammonia in the water and the engineer "determined this discolouration was not wastewater related". Although the engineer took the OHES water quality results into account, no test results obtained from the OHES bottle samples were given in the report.

The engineer then inspected the brook upstream, finding that the colour of the water "changed from blue to green" where the pipe carrying the brook passed underground at Merton Road (a photograph taken there at 22:16 shows a blue-green scum on the water). The engineer went on to Wimbledon Park Lake and found blue and green staining at the outfall weir and the nearby lake edges. The engineer then looked at two manholes giving access to the pipe carrying the flow of Bigden Brook, at the junction of Church, Bathgate, Wimbledon Park and Wimbledon Park roads. This brook carries "surface water" originating in the northern half of the Wimbledon Park Lake catchment and discharges into the north-west arm of the lake, near to the island. This was found to be clear, confirming that the "discolouration originated from within Wimbledon Park and not from the Thames Water network." The engineer "suspected the discolouration could be due to an algaecide treatment applied to the lake".

The report states that OHES visited the site again, but fails to cite the date of this visit and the time (17:16) is identical to the time of their earlier inspection. On this occasion the blue discolouration had gone.

A network engineer returned to the site on 25th July at 13:47, nearly two days after the pollution was first observed, by which time "the clarity of the water has improved". Water quality measurements made then were ammonia 1 ppm, ammonium ion 5 mg/l and dissolved oxygen 69%. The engineer then visited Wimbledon Park Lake, described as "the source of pollution" and observed the signs posted up warning of blue-green algae there.

The engineer "reattended site on 26 July at 16:49 to reinspect the watercourse. The engineer stated the watercourse had recovered as it was a lot clearer with WQ readings of 1 ppm NH3 and DO 70%". This visit was some 3 days after the first report of pollution.

Finally the engineer returned on 29th July at 14:13 (some six days after the first report) and confirmed "all assets were discharging clear water. The NE also spoke to the Wimbledon Park Environmental Technician who confirmed the algal bloom disperses in cold weather conditions."

This report is helpful in two regards:

1. Inspection was made of the underground courses of Wimbledon Park and Bigden Brooks, which are inaccessible to the ordinary public. This showed that the turquoise discolouration had disappeared from all but the easternmost part of Wimbledon Park Brook by 22:00 on the 24th. The report made no comment on the significance of the appearance of the brook at that time, but the photograph reproduced shows what looks very like a blue-green bacterial scum at Merton Road. So the brook was still contaminated, but in recovery a little over a day after the pollution was first spotted. The observation that Bigden Brook was running clear later that evening was less conclusive, as it might be expected that any pollutants would clear downstream and so Church Road would clear earlier than would places further downstream.

2. Measurements were made of ammonia, ammonium ion and dissolved oxygen, all apparently at the Earlsfield end of the brook. The ammonia and ammonium levels exceed thresholds set by the Water Framework Directive and so indicate poor water quality, but not so much as would be expected from significant sewage contamination. Similarly, the dissolved oxygen levels of around 70% would not cause mortality to most fish and so do not indicate significant sewage pollution.  

However, the report is seriously deficient in several regards. 

1. We know that Thames Water undertook further work in the public park on the evening of 30th July, but no report from this was furnished for the Environmental Information request despite my requests explicitly seeking this information. I have made a further request in an attempt to get this information.

2. Although observations were made at one manhole on Wimbledon Park Brook two on Bigden Brook and of the lake edge and outfall weir, no water quality testing was reported for these places, nor for the brook in the public park. The AELTC drain was not mentioned in the report, so we have no information from it. No photographs of Bigden Brook or the lake were reproduced. My bottle samples of the lake and brook in the public park on the 26th July confirmed the blue-green bacterium Aphanizomenon flos-aquae remained abundant in the lake and it would have been obvious to any competent technical inspection made around that time.

3. No account was taken of others' observations of Wimbledon Park Lake and brook, and the visits by and for Thames Water were made well after the first report, and so were less informative is most respects than were others' observations. Under these circumstances, Thames Water's failure to find is no evidence of absence.

4. The conclusion that the source of the pollution was the lake, not upstream, is fatally flawed because one of the two tributaries and the AELTC drain were not observed, and the inspection of Bigden Brook was well over a day after the event. This is most unfortunate, as there seems to be little or no monitoring of the tributaries to provide a background, and an opportunity was lost on this occasion. Our observations confirm that there was a significant blue-green bacterial bloom in the lake around the time of the incident, but we cannot comment on the supposed lack of pollutant inflow to the lake.

5. The visual observations are not commented upon beyond a fear that the polluted water might harm monitoring equipment and an unsupported speculation that the discolouration of the water was the result of use of an algaecide in the lake. The report cites LB Merton precautions on "blue green algae", but fails to evaluate the theory that the pollution was the result of a blue-green bloom.

6. The focus on the origin of the pollution sought a physical location for an event, but failed to examine what may have caused the pollution in the first place. If the pollution was the result of a blue-green bloom, it is appropriate to examine what factor may have precipitated this.

As I have remarked before, these events are inherently short-lived and require sensible observation and testing. The failure to arrive in a timely fashion, to look in the right places, observe sensibly and to test for likely causes means that the Thames Water report is virtually useless.

On September 12th I observed the lake and measured water transparency. We still had a great abundance of Aphanizomenon flos-aquae in the lake and water clarity was low, so another die-off and pollution of the lake and brook was a possibility. To help understand the cause of the blue-green blooms, it's surely time that LB Merton and Thames Water arranged a programme of water quality sampling in both the lake and the three main tributaries. The science tells us that phosphate pollution will arrive in the lake mainly attached to fine particles. So, phosphate pollution of the lake can be reduced greatly by the installation of effective silt interceptors, as has been called for by the Friends of Wimbledon Park for many years. Nitrates arrive from the tributaries mainly in solution and work is required on where these may originate in the catchment, so that we can work to reduce this. "Desilting" the lake, as is promised by AELTC, will not solve the nutrient problem, indeed AELTC seems not to want others to know what they discharge into the lake down their drain. 

When I did my monthly water quality sampling in the lake and brook on the 22nd, water temperature was substantially lower than a month previously and the Aphanizomenon flos-aquae was still abundant, but not blooming and there had been a radical improvement in water clarity. There were a few remnants of the blue-green bloom and turquoise water on the windward shore, but my plankton net recovered an abundance of three species of water fleas in other places. In passing I spotted isolated plants of Corn Marigold and Corn Chamomile in the grassy strip across the brook from the toilet block. These two rare species would doubtless be of planted origin, but I know of no record of when. 

The monthly bird count on the 18th was unremarkable, as most species were quiet now that breeding was over. There were 20 odd Cormorants on the lake doing team fishing, which is a great spectacle. Despite what the anglers may say, these are indicative of good recruitment of young fish this year. The Cormorants come for an abundance of food and push off elsewhere once the depleted numbers don't repay the hunting effort. Cormorant numbers remained high all month. Any problem with fish recruitment is a consequence of there being too little waterweed for those young fish to find refuge. 

The resident pair of Mute Swans started with 8 cygnets in May and attrition cut them back to 6 by August. But, on the 18th there was an interloper accompanied by 4 cygnets and the resident cob was harassing that newcomer, which must have made off, as it was not seen later. However, the extra cygnets remained. Then, two Black Swans arrived on the last day of the month and the cob was busy again harassing one of them. It's interesting that this cob saw the Black Swan as a competitor, in comparison to the various geese on the lake. So, it seems he judges on the shape or novelty, not the colour, of this rival.

The origin of the two Black Swans remains a mystery, as it is illegal to introduce them into the wild in England. There are a few pinioned birds kept under license in collections of wildfowl, the nearest being on the central London Royal Park lakes. So, it seems there is someone breaking their license conditions and allowing free-flighted birds.

At the end of the month, there was another significant blue-green bloom as the, normally bright green, Aphanizomenon flos-aquae came to float at the surface and die, releasing much visible blue-green pollution. I saw two dead fish: a Carp and a Perch, suggesting that the pollution could be toxic, or that the  Aphanizomenon flos-aquae, although not greatly abundant, could deplete oxygen overnight. As I was photographing the fish, I was asked about the bloom and dead fish by a member of the public, who was confused by the conflict between what she saw and the assurance of a LB Merton watersports person that the bloom was "harmless, organic, natural, all over the lake and no problem". Concerned that this apparenetly authoritative advice was at odds with the displayed warning notices, I remonstrated with the watersports person, who denied having said this!

There was a tragic loss of a 150-year old Ash tree by the cafe. This tree was a great visual asset and was established there in 1875, when the area was leasehold farmland, well before the arrival of the District Line and the housing on the surrounding roads and 60 years before the development of the public park. So, it was a link with the past. Notice was given  by LB Merton that it was "compromised due to advanced decay" and despite urging, they were intent on total removal, which went ahead. There are two issues here. First, is the triage of tree works for safety reasons under the Merton Tree Strategy, which could be regarded as excessively precautionary given the established fact that injuries and deaths from falling trees or limbs are so very rare that the Health and Safety Executive regards the tiny risk as broadly acceptable. Second, is the Ash itself. Whilst it had visible bracket fungi, there was no sign at all of die back of the vigorous canopy. Observation of the removal operation with binoculars and of the limbs and trunk sections deposited on the downslope of the dam showed that only a few branches, and none of the trunk, had fungal infection and this did not extend to the sap wood, from which trees derive most of their strength. The decayed parts of the crown could have been taken down as far as the visible infection extended, leaving the uninfected tree to remain. Such sensitive work was apparently not considered despite our urging.

August 2025

I had thought that the Dave Lofthouse Glade might be ready for its annual meadow mow, but in mid month I found it to be quite colourful. There was a scattering of the yellow flowers of Bristly Oxtongue and the Creeping Thistle was flowering again. It appears that the return of rain this month has given these a new lease of life. I have been scattering seeds of Meadow Vetchling there in recent years and this month I found it in flower for the first time. That brings the list of species that have been seen there since meadow management began to 147, this year's total to 52 species and the number found on the day to 35. It will need mowing before the end of September with the arisings racked off. I'm hopeful that Merton Greenspaces will help with this, saving much hand labour.

I did the monthly bird count on the 18th. The geese moult was over and many of them were feeding out in the public park or the grasslands of the ex-golf course, those from the public park making their way back to the lake as dog walkers arrived when the gates were opened at 06:50. The 80 Greylags continued to outnumber the 50 Canada Geese and 20 Egyptian Geese. The Mute Swan pair has been remarkably successful, with seven well-grown cygnets. The three Cormorants and two Great-crested Grebes suggest that the fish populations may have recovered somewhat from the recent dearth. A sole Grey Wagtail was feeding along the lakeside promenade. This species is now established and breeding and also often spotted in the brook.

I have continued to prune back around the edges of the perimeter path where potentially invasive Brambles grow. It's possible to remove this year's arching stems, so preventing them leapfrogging out into the adjacent grassland, whilst leaving the flowering and fruiting spurs to be enjoyed by people and by birds. Sadly, the heavy pruning by Idverde at just the wrong time of year removed flowering and fruiting spurs, not only of Bramble, but also Dog Rose, Honeysuckle, Elder, Blackthorn, Wild Cherry and Hawthorn. These aren't invasive and can be pruned back, if necessary, once the fruits have been consumed. The significant early summer drought has left the birds with less natural food than usual and, sadly, there will be little fruit for them in the autumn also. There's also an aesthetic point, which will be a matter of preference. Pruning with machine tools lends itself to "tidy" clean-edged shrubbery in places where an irregular edge would look more natural. 

There is a heavy acorn crop this year, unfortunately mainly infected by the Knopper Gall wasp. Fortunately some acorns escape infection and are carried off by Jays and Squirrels and buried. Those not later dug up and in the right growing conditions will germinate and potentially colonise. 

 

July 2025

There are two species of bird on the lake that increased greatly when there was a recovery of waterweeds some ten years ago: Mute Swans and Coots, both of which feed on the submerged waterweed. On the 3rd, I noted a third species, not observed before. In the early morning, the geese that feed on the surrounding grasslands make their way to the lake and there were Canada Geese and Greylags there. The Canadas were upending to gather a fresh growth of Fennel Pondweed and consuming it, but the Greylags weren't; an interesting difference in the feeding ecology of these two. It could be that the drought left the geese short of their early morning bite from the grassland and that those Canada Geese were making up for the shortage, but it's interesting nevertheless that the Greylags seemed to lack the ability.

The water in the brook downstream of the cafe was a series of pools with just a trickle of flow on the 4th, accounting for the Water Striders seen there, a species of calm waters. And there was a new species of plant for the park, Elegant Clarkia, growing beside the brook. This is a garden annual originating in California and it remains a mystery how it arrived in this odd situation.

There was just a little easing of the drought on the 8th when there was around 10 mm of  rain, but then we were straight back into another hot dry week. Sadly, the high temperatures and nutrient pollution in the lake led to a significant bloom of blue-green bacteria and water clarity declined greatly early in the month, as has happened in previous years with blooms. I could see the floating clumps of Oscillatoria and the abundance of Aphanizomenon flos-aquae, which is dispersed through the water. Both of these are known sometimes to be toxic. At the beginning of the month the lake level was below the crest of the outfall weir, so practically no water, polluted by blue-greens or not, went down the brook from the lake. However, the old pipe that issues near the toilet block continued with a trickle. This pipe carries the surface water drainage from much of Home Park Road, so clearly there are springs or leaks in this area that provide a tiny flow even in drought times. After the 8th, water flowed down from the weir in the new course of the brook for a day or two, and it was noted that this was milky in appearance and that there were some suds where it flowed over an obstruction. This is typical of lake water with algal blooms and was, therefore, not the result of a single pollution incident, rather of an ongoing situation in the whole lake.

I did my regular lake water sampling on the 11th, when I found the cause of that colour in the brook: a bloom of a blue-green bacterium, confirmed by microscopic examination as Aphanizomenon flos-aquae, This species is unusual, as the individual filaments clump together to form shapes that are visible to the naked eye floating dispersed throughout the water body, looking much like finely-chopped grass cuttings (see the magnified image). I have found this species in a wide range of months (April to December) every year since I first noted it blooming in 2018 and it bloomed also in May and August 2019, September 2021, June 2022 and August 2024 as well as this month. On these occasions I found some pondweeds and plenty of microscopic animals, such as water boatmen, water fleas, water mites and the copepod Cyclops, nor was any unusual fish mortality observed, suggesting that the blooms of this species were not very toxic on those occasions. When Aphanizomenon runs out of nutrients or oxygen it can die off and be seen more obviously as bright green scum accompanied by a turquoise coloration in the water. That's what was seen in the incident after the 8th. Another species, Oscillatoria, bloomed this Spring, between February and April, and was still present, if in reduced numbers. Like Aphanizomenon it can be identified without a microscope as it lives in the top layer of sediment and the oxygen given off by its photosynthesis causes ugly globs of sediment to float to the surface. It has bloomed previously in the Spring of 2023. 

There was a much more significant pollution of the brook with a blue-green bloom on the 23rd and 24th. This was reported in the Putney News on the 30th: https://putney.news/2025/07/30/anglers-campaigners-point-to-aeltc-after-mystery-lake-spill/?bclid=IwQ0xDSwL2pR1leHRuA2FlbQIxMQABHulJqMo3Iii5nqGBCfckoVWQiSx05tP9MFqsrh9_MqfKPsfxeHiiC9_33oxb_aem_G1OERC3RHjGQ-i_NZoyIuw&sfnsn=scwspwa 

This article is remarkably good journalism, but it speculates beyond the present incident, with its headline "Many now believe the spill may have originated from drainage linked to the All England Lawn Tennis Club (AELTC), and fear it may foreshadow far more serious pollution if the club’s expansion plans are approved." We just don't know whether the cause was a spill and we have great reservations about the water quality implications of the AELTC proposals, but that is not our present concern. Here, I focus on the incident around the 24th. 

Before recounting this recent incident, I repeat the occasion when a dog was left partially paralysed by exposure to a bloom in the brook in early September 2022, when I confirmed the organism to be Dolicospermum, which bloomed in August and September that year. The dog was poisoned by the contaminated water of the brook. The samples for blue-greens commissioned by LB Merton in late September, well after the incident, confirmed only Microcystis aeruginosa in high numbers. I had found a tiny amount of Microcystis in previous years and it was there in September 2022, but did not bloom. I am confident it was not the cause of the dog poisoning. It is not identifiable without a microscope. Dolicospermum also requires a microscope for determination and it has been found between June and September in other years, but not since 2022. 

I was out of town on 23rd July, when there were reports of a flow of milky-grey or turquoise water, foaming where turbulent, in the whole length of the brook and of a dog under treatment as a result of exposure to the water. It was first reported where the downstream pipe discharges into the River Wandle at Earlsfield, and the Environment Agency was alerted. Photographs the following day confirmed that it came from the stilling pool which lies below the outfall weir in Ashen Grove Wood, just upstream of the public park. An angler visited the lake later on the 24th, confirming that the milky-grey water was flowing over the lake outfall weir, it was foul-smelling and there were fewer birds by the lakeside promende than usual, and he also reported to the Environment Agency. There were no signs of dead birds or fish. The Council was alerted by the Friends of Wimbledon Park, and posted extra warning notices on the 24th, and also contacted the Environment Agency.

It emerged later that the Watersports Centre had been carrying out visual inspections for blue-green bacteria each morning over the previous month to decide which parts of the lake were appropriate for "wet" activities. This was following a blue-green bloom on Putney Heath, so apparently my previous alerts sent to senior officers of LB Merton did not result in any such action. My most recent alert was an email to the Chief Executive reporting the bloom of Oscillatoria on 1st May this year. 

The dog was affected by entering the polluted water of the brook and kept under observation by a veterinarian on the 24th and discharged unharmed. The dog owner had acted prudently.

Some further background.

Blue-green blooms are most numerous in summer, when light levels and water temperatures are high, but the key factor is excessive levels of plant nutrients dissolved in the water. I have compiled nutrient determinations by myself (most recently through FreshWaterWatch, a citizen science scheme) by the anglers and a very few by others. These results show that the lake has often had moderate or high phosphate concentrations, which could lead to blooms if it were not for the low concentrations of nitrogen. Many blue-greens are able to fix nitrogen, so surviving or even thriving where plants would find the low concentrations limiting. This year, phosphate measurements declined from high levels in April and May to low levels this month, so phosphate appears to have become limiting this month, perhaps causing the mass death of Aphanizomenon, but that's speculation on my part.

The breaking of the drought, accompanied by overtopping of the weir and a flow down the Brook after months of no more than a trickle, clearly explains why a bloom appeared in the Brook on the 8th. Press reports then described thunderstorms at the Wimbledon Championship. The drought returned after that, but there was much more rainfall on the 19th which sent a flood down the brook. On my return home on the 26th, my rain guage showed that 40mm of rain had fallen in the previous week. However, that flood didn't show a bloom. Photographs of the brook taken by Paul Johnson show it was running dirty, but with no colouration  on the morning of the 23rd, yet the first report right down at Earlsfield that evening shows that the bloom originated that day and quickly filled the whole length of the brook. Photos also show that there was a visible bright green scum on the lake beside the promende on the 24th.

The visible bloom was over by the time I was able to take water samples on the afternoon of the 26th, but my samples confirmed that Aphanizomenon was still present dispersed throughout the water of both the lake and the brook, just no longer super-abundant, as it was on the 11th. No other blue-green species was evident then. We, and the dog, had been lucky as the bloom seems not to have been very toxic.

The origin of the nutrient pollution that is a pre-requisite of a bloom remains uncertain, it 
can be excessive bird feeding, atmospheric deposition, bird defecation, and sources in the catchment coming down the tributary pipes, none of which are monitored, including the drain from the AELTC site. It's reprehensible that Merton owns and manages the site and runs the watersports yet does no substantial monitoring, and that AELTC remains silent on what goes down its drains. I, and the anglers, publish our information (me most recently as part of my representations on the AELTC overdevelopment proposals), but we have neither the access nor the resources to monitor the sources.

With a microscope, blue-green bacteria are readily monitored in water samples, as I have been doing for some eight years but, unfortunately, testing for toxicity requires specialist methods not available to the ordinary environmental scientist and an innocuous bloom can turn toxic. Effectively, we are using dogs as a test species, which is not an appropriate approach. This means that precaution is required.

Since I wrote this, it appears that Thames Water have inspected the site. The first occasion was late at night, perhaps on the 24th and certainly that week. On the second occasion, the evening of the 30th, a local lawyer spoke to the TW operatives parked up by the Home Park Road entrance to the public park, who said they were investigating the reports of pollution. I would comment, rather late. I have previously sought to help TW with their investigation of local incidents, finding them unreceptive, but I tried again, getting an incident number 01242268.

 

 

June 2025

As I have monitored the results of meadow and hedgerow management in the park, tensions have arisen.

I did some experimental management of the hedgerows in early June. Some was in the 35-year-old hedgerow on the Tube line boundary between the Revelstoke Road car park and Horse Close Wood. This was established as a joint project between the Wimbledon Park Residents' Association and LB Merton tree officers and is still remembered by some of the school children who did the planting, now in their mid 40s. I also experimented along the 80-year-old hedgerow on the boundary with the ex-golf course north of the Athletics area. Both places had been butchered in the winter with the use of a heavy flail, leaving unsightly broken branch stumps. There were but two advantages of this. First, is the cost, the flail doing work much more cheaply than hand trimming. Second, is the avoidance of the bird breeding season, so avoiding breaking the law by harming the nests of breeding birds. 

Since this butchering of the hedges, the plants had grown back and flowering stems of Bramble, Dog Rose and Native Honeysuckle were showing at the edges of the hedges. The fruits of the earlier-flowering Hawthorn and Blackthorn and the odd late Holly fruits were ripening. A few of the rose stems projected appreciably clear of the edge of the hedge, but there were many arching branches of Bramble without flowers, as is typical. This species flowers on one-year-old stems. These flowerless stems would threaten passers-by if left. So, my experimental management cut back mainly these threatening Brambles, whilst sparing the flowers and fruit, except in exceptional places where these branches stood out from the hedgerow edge. A few Dog Roses were in flower and had arched out, but these weren't long enough to intrude and I left them for people to enjoy, intending to cut them back once the flowers were over. As the work was solely on stems projecting clear of the hedge and was by hand, it was assured not to affect bird nests. Some of the Blackbirds, Song Thrushes, Robins, Dunnocks and Wrens were repeat-nesting after losing their first or second attempts and others had fledged young successfully and were embarking on their second nest of the year. I didn't search for these nests, as it's difficult to find nests in the dense shrubbery and so a search would risk disturbing them, but the birds' behaviour confirmed their presence in the hedge. My experiments confirmed that intrusive growth clear of the hedge could be removed in a responsible way. 

Then, on 11th June, I was surveying the hedge on the boundary of the golf course and was disturbed to find that almost all of the flowering and fruiting stems that weren't any threat to passers-by had been cut off, leaving a straight edge with only a tiny fraction of the previous flowers and fruit. Clearly, someone had decided that the hedgerow needed pruning. They were wrong. Going on round, I found that the same pruning had been done on the eastern hedgerow as well. Not only that, but this trimming went well into the edge of the dense shrubs and alarm calls from Robins and Blackbirds told me that they were in distress. I cannot confirm what was the cause of that, but suspect it was disturbance of nests and their contents. Also, the flowers and fruit removed were no longer there for passers-by to appreciate, nor as sources of nectar and pollen for pollinating insects, nor for birds to consume the ripe fruits later in the season. Wanton harm to the wildlife and its habitat. Now, of course, if you don't survey a hedge before managing it you cannot confirm the presence of breeding birds. Failure to look is failure to find. It's commonplace for people to manage bird breeding habitat in such a way and technically they are not breaking the law. In my view, however, the choice not to look breaks the spirit of the law. At best these hedgerows have been impoverished by the management, at worst protected species have been harmed.

I will be making submissions on the future of our Merton parks in the current consultation. I don't believe that talking to local park users and seeking ways to balance the desires of all park users needs be any more expensive than is management by rote, as goodwill generates voluntary help. And we have a team of Community Payback Scheme people who could carry out sensitive management work with hand tools and could benefit from understanding why this is done. 

As I did the monthly bird count on the 17th, I noted the Dave Lofthouse Glade in Horse Close Wood. The management work by the Friends is paying off. The early colour from Dandelions. Jack-by-the-hedge, Cow Parsley and Yellow-flag Iris has died back to be replaced by Creeping Buttercup, White Clover, Hybrid Hedge Bindweed, Hogweed, Meadow Buttercup and Hedge Woundwort. It looks like a wildflower meadow, even before the summer plants get going. The Cuckoo Flowers in the little triangle near the White Pavilion have died back and the grass flowers of Yorkshire Fog are prominant there now with just the odd Cat's-ear, Germander Speedwell and Nipplewort. The meadow beside the perimeter path south of the brook is also showing a few meadow species, the most interesting of which was a new listing for the public park, Wild Carrot. This species is most abundant in old meadows, so it is nice to find it here. It doesn't like acid soils, being found rather on the chalk in places south of here. So, yet another indication indication that there are no thoroughly acid soils in the heritage landscape. A single Pokeweed plant was seen growing at the base of a Railway Poplar just north of where the brook leaves the park. The odd individual Pokeweed has been seen in the park previously and they can last several years, if not tidied away.

Another nice finding was a Nurseryweb Spider in the veteran oak plot. The mother spider makes a nest around her egg sac and guards her nest whilst the spiderlings are growing. 

Give their great decline, it was good to see that Swifts still commute long distances to catch insects flying over the lake. Numbers are typically very variable, and they come and go, but seeing 20 at once was good. For other birds, much of the song is over, with birds intent on rearing their young, but it was good to hear Stock Doves and Song Thrushes on all sides of the public park. There were just a few Blackbirds in song, but many Wrens, a Blackcap beside the tube line in the east and a Chiffchaff in Horse Close Wood. There was a Great Spotted Woodpecker feeding its young in Horse Close Wood. I wonder if the pre-emptive spraying for possible Oak Processionary Moth has affected any of those species that feed caterpillars to their nestlings. My totals for both Blue and Great Tits were lower than they have been in most past years, but all manner of other things are possible explanations. It will be difficult to prove any adverse effect.

The Egyptian, Greylag and Canada Geese had arrived in the park for their annual moult, when they are flightless for about a month. There were some 120 Greylags, 50 Canadas and 40 Egyptians, all with their still flightless young of the year. At these times, they feed nearer to the lake, so they can retreat to safety out on the water when disturbance arrives in the public park (and also on the ex-golf course where the set-up for corporate hospitality is under way). There were 5 Great-crested Grebes on the lake, and three Grey Herons on the edge, suggesting that some fish are breeding naturally. Sadly, the incipient Heronry seems to have come to nothing this year.

I did the lake water sampling on the 19th. At 26 C, the water was well above the previous warmest June temperature and one degree above the highest in any month before. Sadly the water quality was low. The nutrient story was the same as usual: low nitrate and high phosphate, still suggesting that the lake is nitrate-limited. The Oscillatoria blue-green remained prominent, and the fauna was dominated by Daphnia magna, the big water-flea. People still set their dogs into the water, disregarding the warning notices about "blue-green algae". Myself, I'm careful to avoid exposure to the Oscillatora and I wash thoroughly on return home. Of course, the main risk is Weil's Disease, so it's essential that no open wound is exposed to the water. I found two other blue-greens, but so far not blooming. There was also quite a lot of Ulva lactuca, the miss-named "sea lettuce", and just a little Fennel Pondweed and Rigid Hornwort. I expect that the pondweed will increase and be cleared by the watesports people again, so exascerbating the nutrient problem. Many midges had emerged from the lake recently, leaving their larval exoskeletons behind. It was difficult undertaking a "kick sample" in the brook, as there was only a trickle of water, in many places flowing below the gravel surface, but I did find a large number of mosquito larvae alongside the usual water lice and shrimps. More like pond fauna than that of a brook. 

May 2025

A great time to see spring flowers and birds. I did the monthly lake water sampling on the 15th and bird count on the 22nd. I saw the first Swifts hawking insects over the lake on the 15th, although doubtless they returned earlier than that. So, migration was over, the Swift being the last.

As happens at this time of year, the geese were mostly out on the grass of the Great Field in the early morning before the arrival of the first dogs off the leash sent them to the security of the lake. The gates were opened at 06:20 and the geese had moved within 10-minutes of that. All the geese species had goslings, several groups of Greylags, but fewer of Canada and Egyptian. We have yet to see any Mandarin ducklings, now the second spring they have been present, it should be just a matter of time.

Many wild flowers were seen in May. By arrangement with the parks contractors, a small, triangular, grassy slope by the steps at the south-east corner of the tennis courts is left for two species to flower. First came the pale pink Cuckoo Flower from late April through to mid May and that was followed by Germander Speedwell at the end of May. Both of these are perennials and so the appropriate management is as a meadow: mowing and then raking off the resulting hay in summer, once the flowering is over. Around the edges of the wooded areas Cow Parsley was in full flower, going over to seed by the end of the month in the hot, dry conditions. It was the same story with Stinking Iris, a specialist for dry shade, with flowering quickly over.

The same meadow management is applied to the grassland strip between the perimeter path and the railside hedges on the south-eastern side of the park. In both places it is taking time for the flowers that have long been supressed by scheduled mowing to return, but we have more than daisies to enjoy. Dandelion, White Clover and Creeping Buttercup flower there, "weeds" where they invade a tidy lawn or cottage garden border, but here wildflowers. These meadows have been managed appropriately following good consultation between Idverde contract staff and the Friends of Wimbledon Park, but sadly this is the exception. And, even here, not all is well. The edges of both places have been sprayed. Sadly, this is the case also for the perimeter of the stadium, where a good range of plants colonise and would soften the ugly, bare bases of the Leyland Cypressus were they given a chance. If allowed, Ivy would green the bare ground, the Herb Robert, Sow thistles, thistles, Round-leaved Crane's-bill, Creeping Buttercup and Black Nightshade are modest plants, showing promise in April, withered and dying from the spray in May

Dog roses were in flower both where they colonised naturally, as in the hedgerow beside the golf course in the north and below the Veteran Oak, and where planted beside Horse Close Wood and in the newer hedgerows. By the end of the month Bramble was just beginning to flower in these same places.

The vegetation of the brook was looking good, with the planted Yellow-flag Iris and Brooklime and the naturally colonised Watercress. In the protracted drought there is but a trickle of flow in the brook most of the time, much of that deriving from surface water drainage from the Home Park Road suburbs, rather than the lake outflow where there is a small residual flow down the Eel pass only.

At the end of April topsoil and grass seed were spread over the worst of the bare patches in the Great Field, a great boon for the Feral Pigeons that gleaned much of the seed. One hopes that the grass seed wasn't treated with insecticide. Sadly, the drought prevented any germination.

The watering of the bowling green was a boon for the Starlings commuting to and from their nests with food, and later bringing the fledglings to it. Perhaps an act of desperation, as the grassland invertebrates elsewhere had been decimated by the drought or forced to go down in search of moisture. This will affect other species, like Blackbirds, that risk predators at this time of year to venture out of shelter to find food in the open grass. 

 

Consultation

There is a consultation under way on the future of Merton's parks, with Idverde's contract coming to an end soon. One fears a continuation of one-size-fits-all actions, perhaps inevitable in a cost-effective contract. Nevertheless, many problems could be overcome with improved consultation with parks users and friends groups. Here, I relate how consultation has worked well for those wanting a more natural aspect to the vegetation of the park and lack of consultation has not.

The natural character of the park has suffered from failures of consultation and by continuation of past practices. It's all too easy to mow much more frequently than is required by the use. A place where this happens is the Crazy Golf area. This is one of the best grasslands in the park, but that is hidden when it's scalped to a schedule and the hay left on the surface as a thick mulch, suppressing the regrowth of wildflowers. Meadow management is needed here and the results celebrated. Raking off such big areas could be done if the mowing was on a meadow schedule, coordinated with volunteers or the Community Payback team. Alternatively, it could be mown with a machine equipped with a grass collector, so obviating the need to rake off. 

Another excess was the use of a flail machine to cut back the hedgerows around the perimeter of the park. It's great that this is done in the winter, so avoiding the bird breeding season, but that leaves garish scars there until late spring growth comes to cover them up.That winter hedgerow work would be much more sensitively done with hand tools, perhaps again by the Community Payback team, with help from volunteers. Hedgerow work in the bird breeding season needs to be much more sensitive, which is only possible with careful use of hand tools. This also allows the flowering and fruiting branches to be spared and to be enjoyed, being pruned back once the birds have taken the fruit.

When the Lofthouse Glade was developed at the eastern end of Horse Close Wood, the Friends of Wimbledon Park asked for the heavier management, the meadow cut, to be included within the maintenance contract. The Friends would do the raking off and spot control of invading trees and shrubs. Without this cooperation and coordination, the Friends are left cutting the meadow with hand tools, an onerous task. 

A difficult issue is the spraying of  "weeds" around the paths, fences, standard trees, seats, notice boards... well everywhere that a mowing machine cannot easily access. Some people resent the unsightly dead grass that results and don't like the idea of their children getting contaminated when investigating the flowers unaware they have just been sprayed. In most cases the contract could redefine some of those "weeds" as wildflowers, tidied by hand or a strimmer once the flowering is over, and we can accept some vegetation at the edge, between paved paths and grassland, again cut back occasionally. Pathside plants once provided food for House Sparrows, but now we have neither the sparrows nor the plants. Needless spraying beside the hedge in the north beside the ex-golf course has prevented establishment of the valuable hedge-bottom wildflowers that grow there naturally, instead there's a strip of dead grass from the spraying. Hedge bottom plants need cutting back, but not very often. Merton's parks contract need employ no weedicides.

A one-size-fits-all approach also applies to schemes that are rolled out across Merton's parks. These schemes are efficient and so deliver improvements in a cost-effective way. There are also one-off initiatives led by elected members, a valuable connection between local democracy and action. Sadly, however, there is little or no consultation with local volunteers on these borough-wide initiatives. Trees arrive unannounced and at odds with a long-term local programme of planting. That programme was developed using volunteers planting to fill the gaps left by the 100-year-old poplars that are going one by one as they become dangerous and to provide a wooded boundary, reflecting the Capability Brown heritage. It was designed in co-ordination with Merton tree officers. This Council-volunteer partnership thought through what species to plant and where, raised the finance and the planting was done by volunteers. Clearly the institutional memory of Merton Greenspaces is poor, or this local initiative is seen as trivial, for whatever reason there is no consultation with locals. 

Perhaps the most gross problem, however, comes from schemes imposed upon the park by Merton's development planning. AELTC needed to prove a "biodiversity net gain" in their proposed gross overdevelopment of grass courts on the golf course. Unable to prove the gain within their area, they needed places to flag up as "gain" nearby. There's been no real consultation on these proposals in the public park, which were developed late, inadequately described, and buried amongst hundreds of other documents, nor any acknowledgement that there are existing programmes of work in the park. These proposals would deny most of the lakeside promenade to the public. New path diversions are proposed. Without consultation, we don't know if park users really want to see the promenade wholly devoted to watersports? And, if we want this, are the proposed path diversions designed for disabled access? Another AELTC idea is for Horse Close Wood car park. There has long been a proposal to return this back to woodland, but, hidden away in the "gain" is a proposal to upgrade the car park for continued vehicle use. Other planting proposed by AELTC affects places that are part of the 10-year community tree planting. It would be great to get some capital investment into the park, 100 years after it was originally laid out, to refresh tired facilities and reflect community wishes. Locals will be able to help find constructive projects, after all it's our park. But the urgency of statutory planning approval dictates that we will not have a consultation on the proposals, we are meant to simply welcome them. 

I could go on. It's difficult to consult, it takes time and needs willingness. The most vital test of the success of Merton's parks going forward in these cash-strapped times, will be a willingness to discuss and consult, and to work together with locals. 

The meadow triangle

Cuckoo flower

 

April 2025

There seems to have been a radical change to the lake water. The Oscillatoria that arrived this spring has persisted. After arriving in February, there were just a few floating clumps during the dry period in late March and the first half of April, but the return of westerly winds on 17th April led to a visible accumulation of this blue-green beside the promenade on the public side of the lake, around the watersports jetties, dissipated again by the 19th with the return of easterlies. So, the obvious signs of this bloom migrate around the lake with the prevailing wind, but it remains there on the lake bed and floating up to the surface. The experts tell us that blooms are often poisonous with liver or nerve toxins known collectively as cyanotoxins which are typically observed in at least half of the blooms analyzed (see, for example review papers by Prof Linda A. Lawton). Determining toxicity, however, requires specialist analytical methods, inaccessible to the ordinary laboratory or citizen scientist, so one should be precautionary and assume all blooms are toxic to animals, especially dogs, but also us. Oscillatoria is the fourth species of bloom-forming blue-green bacteria found in the lake recently. It is urgent to deal with the excess nutrients in the lake to return it to better health. LB Merton and AELTC assume that the solution lies in "de-silting", but without citing any peer-reviewed science to justify this assumption. My reading of the literature suggests that the preferred method of removing sediment from the lake would make the situation much worse, rather than better. It's surely time for AELTC to spend just a little money actually studying where the excess nutrients come from and looking at the existing published studies for the soluion.

I have taken part in the citizen science Waterblitz, Big River Watch and Freshwater Watch whenever one is run. They did this on 25th-28th April and I took part. As usual the lake scored high on Phosphate at 0.35 ppm, but as unpolluted for Nitrate, also 0.35 ppm. This tells us that nitrate is the limiting nutrient and helps to explain why Blue-green bacteria do well in the lake, as they can fix atmospheric nitrogen. The Anglers have been monitoring lake water quality on and off since late 2022 and you should consult their website for their results, but suffice to say that they agree that phosphate levels are high (indeed their kit gives consistently higher phosphate than the citizen science kit). Unfortunately, the anglers' nitrate measurements, whilst agreeing that there isn't much are mainly zero, which makes no sense. I suspect their kit is not sensitive enough for nitrate. Helpfully, the anglers also measure ammonia and most of their measurements of it show no pollution.

That's the bad news, but the good news is that there's much to celebrate in the park. The native Bluebells, Dog's mercury, Lords-and-Ladies, Wild cherries, Hawthorn and Jack-by-the-hedge are flowering in the woodlands and hedgerows. Stock doves, tits, Green and Great-spotted woodpeckers, Chiff-chaffs, Starlings and Blackcaps are breeding. Bees are collecting pollen and nectar from those native plants and also from Green alkanet. None of these plants are named in the lists of "pollinator friendly" plants pushed by the popular media, but the bees have the answer. There's a pair of Mandarin ducks on the lake again this spring, and the male has been on his own recently, so the female is probably on a nest in one of the few veteran trees that AELTC have spared in their tree works. After months without any, a pair of Great-crested grebes has returned to the lake to join the Tufted ducks, Pochards, Grey herons and Mute Swans. The grebes give us hope that the fish may be breeding successfully again.

March 2025

With the arrival of spring, Blackthorns were in flower early in the month. The temporary ponds were drying up, for example the one beside the Lofthouse Glade

October 2024

I did my monthly bird count on the 28th. This confirmed that Grey Herons are now more numerous on the lake, perhaps because they are nesting on the island.

Leaf fall had begun, with most Lime trees mainly bare, Oak less so, Ash and Elm just beginning and the Weeping Willows had yet to shed any leaves. Ivy was in flower, providing valuable nectar for insects at a time when most other flowering was over. Some Elms were falling over in Horse Close Wood, perhaps the third die off since the virulent strain of Dutch Elm Disease took all the tall trees in the 70s.

The "Wildflower" plots around the Great Field had been mown off, so sacrificing a scattering of late flowers.

A new fence had been erected over the Brook where it flowed from the AELTC land into the Public Park. This will make it harder for the youngsters who would use the land around the lake outfall to have a quiet time undisturbed by other park users. 

The ex-golf course had been mown, making it more difficult to see the quality of the grassland.

September 2024

When I did my monthly bird count on the 17th I found that one of the four young Mute Swans standing by the main watersports jetty was trailing a length of fishing line from its leg. It was already tangled in twigs, waterweed and other debris, disabling the bird. Fortunately it was tame enough that I could catch it readily and remove the barbed hook. I saw all the swans in subsequent days, so it appears that the bird recovered. Grey Wagtails have long occurred in small numbers around the lake and occasionally on the brook in the public park, but I have the impression they are now more frequent, perhaps as a result of the substantially longer stretch of open brook available for them.

On the night of the 22nd-23rd there was significant rainfall, which hit the national news because of the "sink hole" in the corner of the AFC Wimbledon pitch, some 1.5 kilometres away to the east. Unfortunately, I don't know just how much rain fell in the catchment of the lake (which includes much suburbia to the west and extends as far as the Windmill and Rushmere on the common), but there was a significant flood in the park. If anyone used a rain guage and got the figure, it would be of interest to know. The new outflow to the lake performed according to design and dumped the excess water straight into the stilling pool in Ashen Grove Wood, from where it rushed down to quickly flood areas all around the cafe and the crazy golf. That the flow went this way, means that the dam safety works were successful as there was no overtopping of the dam, so no risk it would fail. A very big rainfall would overtop the dam between the watersports building and the stadium entrance, but I heard of no overtopping there. Again, if anyone was there to check, please let me know. However, the flood revealed significant design faults in the new parts of the brook. The engineers had made a last minute design change to the part of the brook within Ashen Grove Wood, down to the toilet block, saying that this change should perform OK. But, it didn't. The bed of the brook was badly eroded, washing away much of the landscaping and wooden steps and eroding the underlying London Clay. Three pipes that had been buried below the bed where they crossed the brook were now exposed at the bottom of the brook. Clearly, this part of the brook is eroding its own course. Just how this can be remedied remains to be determined. 

I'm not sure what the pipes carry: perhaps sewage from the golf clubhouse and fresh water supply, possibly, gas or electricity. Whatever they carry, the intregity of the pipes may be in doubt as they are now subject to flood flows, where previously they were supported by the surrounding clay soil.

It appears that the flood in the public park was exascerbated by debris washed downstream and accumulating on the grille near the payment booth. This acted as a dam and the water backed up and overflowed the path and down beside the crazy golf to make its way back to the downstream part of the brook. As usual, when the park has a flood, the water entered the equipment store beneath the cafe. The debris that blocked the grille perhaps originated at the upstream eroded part of the brook, but anything loose would have joined it. At the other end of the large diameter pipe that runs under the access road to the cafe, recent works have allowed the grille to be removed. This is fortunate, as previously debris used to accumulate there where it was very difficult to remove. This second grille has been left off. It has long puzzled me why there needs to be grilles on this pipe at all. It was rumoured to be for public safety, but I don's see any special safety issue with a short length of large diameter pipe. With or without these grilles, the third grill, on the pipe that runs under the tube line embankment, would have blocked and the flood would have been just as great.

Flooding in the public park is entirely expected, as I pointed out at the LB Merton Council Meeting that approved the works to the dam and brook. The engineering reports made it clear that the new downstream works would prevent any worse flooding than before, not make the situation better. The reason for accepting this is that it was decided to maximise the depth of the lake and so sacrifice the ability to use the lake as a temporary storage for storm flows. The dam safety works, therefore, send much bigger volumes downstream in a flood peak than before, requiring more storage in the downstream brook to prevent much bigger floods there than before. Council Members were misled by their officers when the works were approved. Effectively, flooding in the public park is by design choice. This means that the park is used for temporary storage of flood water that would otherwise overcome the pipes downstream to the Wandle, or even flow under the railway bridge at Revelstoke Road to flood the grid. All this would be prevented were the weir at the lake outflow be lowered by 20cm or so. Then the lake, rather than the public park, would act as the temporary flood storage. One wonders, also, about the wisdom of effectively using the tube line embankment as a dam to hold the flood waters back in the park, so protecting residential areas downstream. That embankment was designed to carry trains, not as a flood control structure. Might it fail? 

The flood we saw was well within the designers' maximum flood. We will certainly have much bigger floods, it's just a matter of when. The maximum would flood most of the tennis courts and right up to the Revelstoke Road car park. It would rise nearly to the level of the floor of the cafe. 

Birds benefitted from the flood. I saw a Little Egret and two Grey Herons in the crazy golf area scavenging the fish that were carried over the weir by the flood flow.

Another interesting observation this month was confirming the identity of a large-leafed plant under the hedge on the south-east corder of the stadium. This was Deadly Nightshade, Atropa beladonna, and just the third record of this species I know of in a wide surrounding area. There was a plant on the tube line embankment a few years back, but not seen recently, and a large plant in the St Mary's Wimbledon graveyard. This species does well in disturbed, chalky soil and is doubtless spread by squirrels, or birds that are not susceptible to the poison. It favours disturbed chalky soils, in these places probably concrete as the local soils are not chalky. I have seen more than one white-flowered Cyclamen in Horse Close Wood this year, perhaps liberated there by people after flowering of a house plant ceased.

There were several waterbird corpses and ill-looking birds this month, probably bird 'Flu. The blue-green bacterial bloom diminished over the month as temperatures cooled and was virtually gone by the end of the month. The predominant species this year was Aphanizomenon flos-cuculae, which seems not to have harmed any dogs this year. I was rather disturbed to see much watersports activity through the months when the bloom was obvious.