The pond story
A large pond is a crucial habitat for any wildlife garden. The first Roots and Shoots pond was built in 1989. When David came into post in 1999 it was seriously degraded, holding little water. So, it was rebuilt winter 1999/2000. Ten years later it had become overgrown and shaded and needed more serious work again. With funding from the charity Froglife this ‘old pond’ was completely rebuilt over winter 2010/2011 with a contractor and a new style of liner.
The 1989 pond was planted with a wide range of native pond plants, including greater reedmace (Typha latifolia), Common Reed (Phragmites communis)and Marsh Pennywort (Hydrocotyle vulgaris) — all three of which had completely filled the pond by 1999. Furthermore the reeds had punctured the pond liner — reed has rhizomes that get everywhere beneath the base of the pond and under pond liners and the new shoots are both very sharp and very persistent. Reed beds, a fine feature for the area of a large pond, should, therefore, be kept well separated from the pond if a butyl liner is being used. There was little permanent water in the pond in 1999 and although there was an excellent population of frogs and common newts, there was little variety in the invertebrate life to be found during the (very difficult) pond dipping sessions.
During January and February of 2000, therefore, the pond was emptied and dug out. A large quantity of the original water was kept in water butts and old dustbins. The newts and frogs began to return as the work was being done – which enabled a complete capture of the population (they were temporarily housed in the water butts).
We recorded 250 adult newts and 50 frogs. The earth removed, plus more clay, was built into a ridge across the original pond – isolating the reed bed to give roughly 2/3 pond, 1/3 reed bed. The job had to be done quickly, both to house the returning amphibians and because of other work programmes. The depression was re-lined with thicker butyl liner to form a new, deep pond within the original pond liner. It was hoped that the new shape and ridge would allow some control of the invading reeds that would undoubtedly attempt to re-colonise the pond. At the same time improvements were made to the rainwater capture system installed in 1989 which fed rain from the greenhouse roof underground to the edge of the pond. This supply was more than enough to keep levels high for the next ten years.
It was then re-stocked in spring 2000 with Water Mint (Mentha aquatica), Water Forget-me-not (Myosotis scorpioides),Curly Pond Weed (Potamogeton crispus an oxygenator), Purple-loosestrife (Lythrum salicaria), Water Plantain (Alisma plantago-aquatica), Great Spearwort (Ranunculus lingua) and Flowering Rush (Butomus umbellatus). The original white water lily (Nymphaea alba), which had not been flowering, was rescued and re-planted. It has recovered well and flowered well for 3 or 4 years.
The newts increased even beyond the 250 population size of February 2000, with the frog spawn of March completely surrounded by a nibbling ring of adult newts and by June it was estimated to be around 750–800 strong. It was so easy to see adult newts, with so many rising for air at any one time that a female blackbird with chicks devised a method of hunting that seems to be unique and unrecorded elsewhere. She would sit on the edge of the pond dipping platform watching the pond. She would concentrate on a newt rising. Just before it broke the surface she would take off and scoop the newt out of the pond in flight with her bill just at the moment that it took its gulp of air. She landed on the ridge by the reed bed, adjusted the newt in her bill then flew back to the concrete flags by the dipping platform. Here, the newt was beaten to death then carried into the cherry tree above where the blackbird chicks waited. Getting it down the chick’s throat was the next challenge. She would repeat this many times during the day and so was a significant predator and population control.
“There’s only one thing better than a pond”
Each year the species records showed the gradual colonisation of the pond by an increasing variety of invertebrate life — two damselfly species in the first season, a third species in 2003, mayfly and caddis fly species, two water boatman species and so on. The Azure Damselfly (Coenagrion puella) also dramatically increased its numbers in 2003. Using a grant from the Walcot Educational Foundation (Lambeth Endowed Charities) David purchased microscopy and video equipment enabling us to run our first pond microscopy project for National Science Week – “LAMBETH’S LIVING WATERS” in 2003. Local school children were able to see and draw an excellent range of microscopic species at high magnification, some quite unusual (for example , the ciliate Stentor). For more details of the invertebrate records see the species lists section. As an arts-science project “Lambeth’s Living Waters” was run again in 2008, this time including a Scanning Electron Microscope set up in the Wildlife Garden Study Centre for the Open Weekend.
At the start of 2004 a second pond was dug for the garden (“There’s only one thing better than a pond – two ponds” – Simon Geikie, newt man). This was in the Paradise Corner and is a more formal-looking, square-shaped pond. Jason Inwood, trainee at the time and keen on all things wild, helped dig out the pond and we found the foundations of the walls of part of the building that once occupied the whole wildlife garden site.
It was impossible to get this wall out but Jason found alongside it that he could keep digging – they must have back-filled with sand after building the original wall. Part of this pond is thus nearly two metres deep! The internal geometry of the pond is also complicated because of this wall – with several different depths. It should, therefore, be an interesting pond with a range of habitats.
Both of our ponds, however, suffer from being surrounded by too many trees and shrubs – shading the ponds too much for many invertebrates and introducing a lot of leaf debris. Although not affecting the value of the ponds for amphibians and some wildlife, they have become less and less favoured by damselflies since around 2006, with non breeding from 2007. Many carnivorous invertebrates using ponds for their larvae prefer the water to be clear and well-oxygenated with good, but not congested, vegetative growth. Clearance work was needed to get the trees back to where they were in 2003 before it could be re-colonised by such species.
2010 – OUR SECOND RE-BUILD!
In early spring 2010 it was decided to remove the large cherry tree on the south side of the old pond. It was planted too close to the pond and was not only becoming very large, it was also sending out suckers from its roots that were emerging around the edge of the pond and even on the opposite side in the meadow! Cherries are not recommended for this reason. Removal immediately improved the light levels in the pond. The demands from visitors and schools wanting to use the garden, however, prevented further work. Later in the summer of 2010 we were approached by Alex Draper of the charity Froglife. He had some funding left from a project and offered to rebuild and expand the pond with a new style of liner. This required clearance of vegetation and the old liner first, before the Froglife contractor could come in to excavate a much bigger hollow for the new pond. Faithful volunteers again came to David’s aid and with Matt, Amy, Brenda, Caroline and a group from Deloitte’s the ground was thoroughly prepared. Before the clearance the pond looked like this:
After vegetation clearance, on 15/10/10 it looked like this:
The liner from 1999-2000 is visible in the centre of the picture. That on the right beneath the Indian Horse Chestnut is the liner from 1989. We carefully pulled the liner of 1999-2000 out so that it could be re-used, exposing the liner from 1989. The tougher butyl liner of 1999 had withstood the attempts by reed shoots to puncture it (water levels had never been a problem between 2000 and 2010), but it was clear that the thinner 1989 liner beneath it was in tatters. Beneath the edges of the liner we found several slow worms of different ages preparing for the winter. They were re-located carefully to the massive pile of sticks and prunings on the path to the Dragon’s Den.
The construction of the new pond took place from November to December, 2010. The new liner is one using granular bentonite sandwiched between two layers of landscape fabric. This comes in large rolls and can be laid out across a new excavation. When re-hydrated the bentonite granules expand completing a perfect seal between the fabric layers and across the joints between sheets. This is a long-lasting, more reliable style of liner than butyl and can produce a beautifully natural-looking pond.
The newly sculpted hole is shown, left – we made it as large as we could from the edge of the dipping platform to the Indian Horse Chestnut and with a natural round shape and profile. The bentonite liner requires a shallow gradient on the sides of the pond (which is better for amphibians and other wildlife). Joints between sheets of the liner are sealed with extra bentonite (centre). The whole liner then has to be covered with 30cm of soil fill (as infertile as possible). Alex Draper of Froglife is shown removing the largest of stones and bricks from the deepest part of the pond, right.
We are very grateful to Alex, Froglife and their funders, Grantscape, for making us this new pond.
As the pond was nearing completion David Sawyer, Roots and Shoots’ longest and most faithful volunteer (running the accounts), won a ‘Local Hero’ award. He decided to give most of the funds from this to David to build a completely new and much larger timber deck to act as a pond dipping platform (replacing the small narrow timber and concrete platform). The pond life contractor built this in January 2011. It was harder to construct than with a butyl lined pond – as the shallow gradient of the pond and avoiding putting posts through the new liner makes it difficult to get enough ‘overhang’ to the new water’s edge. A butyl-lined pond can be made with a vertical slope over which decks can hang.
The pond was then allowed to fill naturally through the rest of the winter – the snow started it off. The pond edge would come close to the birch logs in the photo, right.
Hard work on the margins of the pond, around the decking platform and planting saved plants from the old pond and bringing in new plant species – along with the powers of life to colonise and grow – quickly transformed the pond (above, the first algal bloom in February, and right, later in March). In the spring when there was still a large amount of mud around the edges children and other visitors were able to watch the red mason bees excavating mud from fox paw prints just below the edge of the platform, for example. They could be seen carrying the little balls of mud back to the Trellick Bee Tower to build their nests.
The mud also attracted a new animal for the garden – a quite remarkable relative of grasshoppers – that swims! – an excellent ‘breast-stroke’ with its rear legs. This is the slender groundhopper Tetrix subulata.
By July the area was fully vegetated and was producing excellent wildlife and educational ‘outcomes’ (below).
As early as April the water crowfoot was growing well and flowering and providing an excellent habitat for feeding flies, cool frogs, stalking newts, resting caddis flies, honey bees looking for water, backswimmers (‘greater water boatmen’) waiting in ambush, diving beetles doing the same – perhaps waiting in ambush for each other! By July we had recorded large numbers of the water boatman Corixa punctata and the backswimmer Notonecta glauca; good numbers of the diving beetle Acilius sulcatus; the dragonflies broad-bodied chaser Libellula depressa and – later in September the common darter Sympetrum striolatum; the large red Pyrrhosoma nymphula and azure Coenagrion puella damselflies – and we had the nymphs and larvae of all of these in the pond-dipping trays with children.
The patrolling male broad-bodied chasers gave wonderful displays. allowing close views and contemplation of their flying skills -dragonflies have been doing this (without human observers) for around 350 million years! At Roots and Shoots they were admired by many school children, a permaculture course and local garden visitors from May to July. Their nymphs were turning up in trays from July and August.
