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Spring 2010

posted 13 Dec 2010, 09:57 by Stephen Taylor   [ updated 25 Jul 2011, 16:12 ]
by Tony Ghilchik 

A few days of glorious spring sunshine and the very muddy Heath, especially on the lower slopes that over lie London Clay, becomes just a memory. One of the results of all the winter rain has been a delay in remaking the path shared by pedestrians and cyclists going from the Viaduct Path across to the Highgate Ponds and Millfield Lane. Work was due to start in mid February; however, not only was the ground too wet then but also the contractor refused to guarantee that the proposed rolled aggregate surface, designed to discourage cycling at speed, would not be washed away by further heavy rainfalls. An alternative hoggin surface, more durable yet still avoiding the very artificial look of bonded gravel, has been chosen in its place.

Wild Service trees on the Heath 
The Wild Service tree (Sorbus torminalis) is one of our rarer native trees which arrived in Britain some 10,000 years ago and is now usually confined to pockets of ancient woodland, especially oak and ash woods, or growing in old hedgerows. It prefers clay and lime based soils. The fruits need open sunlight to ripen and our summer temperatures are often too low for the seeds to mature. This, combined with the seeds then needing several weeks of freezing temperatures to germinate, means that its principal method of propagation is by suckers. The fruits or ‘chequers’ are edible and, when over-ripe, taste rather like dates; they were an ancient remedy for colic (hence the torminalis, meaning ‘good for colic’, in its Latin name). Before the introduction of hops they were used to flavour beer.

A 1996 survey by the London Natural History Society recorded thirty-two Wild Service trees of various ages on the Heath. Although some of the older larger ones have been lost (one of a pair growing beside the Seven Sister Ponds on the Extension fell a few years ago) there are also some groups of developing young trees – including a group of young saplings growing beside the Cart Path on the Extension. 

 A recent survey by the Hampstead Heath Tree team came up with a total of eleven mature trees (those with a diameter of 30cms at 1.3 metres above ground level) on the Heath, and with another eight in Kenwood. Of the mature trees on the Heath, five are Veterans located within the historical field boundaries on the Heath and Heath Extension. Two of these Veterans have lost substantial main limbs within the past couple of years and individual management plans are being drawn up to extend the life of each of the five Veterans. The Tree team have made a start on the essential work needed on two of the magnificent Veterans beside the path between the Hollow Beech and the Bird Bridge, and plans are underway for transplanting some of the young saplings into suitable locations along the old hedge boundaries, where they will be able to produce their own suckered progeny.

Pond life 
You will also see work around the ponds to encourage amphibians. This will be aimed at increasing the amount of light to the edges of ponds by coppicing and lifting bank-side trees. The Men’s Pond has suffered the most serious decline in amphibian numbers and although it is particularly important to lift its bank side vegetation, the prolific plant growth on the Heath side of the pond is an unusual bird habitat so we have asked that the lifting is done in sections to retain some of the cover and that more ramps are formed along the bank to made it easier for waterfowl to leave the ponds. Other work will include planting emergent and floating vegetation, creating more new small ponds or pools, and removing vegetation from overgrown ponds to maintain some open water.

All this follows from surveys of the larger Heath ponds over the past ten years which, although showing an overall gradual increase in frogspawn and decrease in toad sprawn, the trend patterns of the different ponds vary enormously with reductions caused, it is thought, from a combination of a lack of emergent and aquatic vegetation, from shade from overhanging trees, by hungry fish or, at the other end of the scale, by the clogging up of a pond by too many plants.

Over in Kenwood the historic Inner Circuit Path in South Wood, going along the south of the Wood Pond, has been closed for some months for safety reasons because a veteran oak in the centre of the path was severely decayed. Kenwood is famed both for its ancient trees, which gave the South Wood its Site of Special Scientific Interest (SSSI) status, and for its historic walks. The options were to retain the tree and keep the path closed, or either to reduce the tree to a safe monolith or to fell it, leaving the dead wood in the wooded area. Ecologically, felling is thought to be better for beetles, though not so good for woodpeckers, and felling would allow the re-opening of the path with its continuous views of the House across the pond.  There were good arguments for either option and English Heritage staff were divided on the best course of action. 

This internal dilemma was apparent in the responses they received on consulting members of the Kenwood Landscape Forum, and members of the Heath Sub-Committee were also very divided on the issue. English Nature was consulted and considered there were sufficient other veterans in the wood for this one not to need to take precedence over the historic path. English Heritage, therefore, took the decision to re-open the path after doing the minimum work to the tree to make the path safe. The tree was too unsafe for the arboreal work to be done from the tree itself and it is hoped that the contractor will be able to use coronet cutting, a technique often now used by the Heath’s tree team, which leaves a monolith looking as if it is the result of storm damage rather than a chain saw. By the time you read this, you will be able to walk the re-opened path and see how successful the work is.

Springett Lecture October 7 
Finally, please make an advance note in your diary for this year’s Springett Lecture at Rosslyn Chapel on Thursday 7th October when we are delighted that Oliver Rackham will be the speaker. We expect him to attract an audience too big to fit into Burgh House so will be hosting his talk at Rosslyn Hill Unitarian Chapel

Professor Rackham is a Fellow of Corpus Christi College, Cambridge and an authority on the British countryside, especially trees, woodlands and wood pasture. As usual, the doors will open at 7:30 for a glass of wine before the talk starts at 8pm. We are expecting a very full audience so please plan to arrive early.