22nd November 2017
Launch of ATF London
Greg Packman, an arboriculturalist with the Royal Parks, writes about the recent launch of ATF London held at Kensington Gardens in October.
The meeting started off outside the Kensington Gardens park office where we had an introduction from Simon Richards, Park Manager of Richmond Park and Head of Park Operations for The Royal Parks. Through his role at Richmond Park with its 1000 plus ancient trees, Simon has worked closely with many from the ATF over the past 20 years so was the ideal person to introduce the first meeting. After a brief introduction from myself and then from London Tree Officers Association Chair, John Parker we set off for the first veteran tree.
Part of the reason for the starting point was that we would walk past a view that looked over the lakes and statues of Kensington Gardens, all the way to Kensington Palace. This is a spectacular view that is said to be one of the longest views in London uninterrupted by a building. Unfortunately on the day it was very overcast so the view was obscured!
A short walk along we came to the first veteran Sweet Chestnut: a wonderful short, squat tree that is said to be one of the original plantings when the Gardens were formally landscaped by Charles Bridgeman for Queen Caroline. This would give the tree a rough planting date of around 1730. The first and most obvious factor about this tree to be pointed out was the absence of mulch or leaf litter. Kensington Gardens is a formal park but it does have areas of less formality, where brambles are allowed to grow, the grass is much longer and the leaves are left in place; this tree however, sits adjacent to a pathway which is part of the original landscape plan and is part of the more formal section. As a result, with landscape pressures and public usage, there is less scope for an area of mulch or leaving the leaves. That is not to say that nothing will be done for the rooting environment for this tree; a perspective was given from the leaf management at Kew Gardens where the leaves are shredded and left in situ to be pulled into the soil.
A very convincing case for the retention of leaves and change of mowing around this tree was given by Jill Butler. Ted Green then gave a very interesting talk about an ‘aerial pruner’ fungi he had seen on a decaying branch on the Sweet Chestnut; how the fungi degrade the branches in the canopy that the tree is no longer uses which then fall to the ground and are decayed into the eco-system. These were the tree surgeons before tree surgery! Regarding the leaf clearance, all green waste is collected and composted in Kensington Gardens then redistributed back to the soil. It may not be as ideal as leaving in situ but it is a good compromise where otherwise nothing may be put back into the soil.
From this tree we headed towards a monolithed Horse Chestnut but stopped briefly by a sapling Oak tree growing from the grass. Jill Butler gave a talk about the natural regeneration and succession of self-sown trees and how rare it is to see this in a landscape in Central London. It is worth pointing out though that native Oak trees and Sweet Chestnut are allowed to grow but Turkey Oak and Red Oak are removed as they will dominate the regeneration if they are left unchecked.
When we got to the monolith the discussion was about the importance of retaining standing deadwood/decaying wood habitat; standing wood provides a different ecological niche which is retained much less often than logs and branches on the ground. This tree was monolithed as it had basal decay and a substantial lean, and is in a very well used area. When Honey Fungus emerged at the base of the tree last year the decision was made to monolith the tree: reduce the risk but retain the habitat.
I also wanted to highlight this tree, as to me, it is a good reason as to why something like the VetCert scheme is so important. To those who don’t know, the VetCert is a pan-European certification scheme for veteran tree work for arborists which is currently being developed by the ATF and partner organisations. The tree surgeons we worked with for this tree had no prior knowledge of veteran tree management and were quite perplexed about coronet cuts or natural fracture techniques.
From this tree we went to an area toward the middle Kensington Gardens. We looked at two more veteran Sweet Chestnuts, which despite being a similar age, were drastically different condition wise: one appeared very healthy whereas the other appeared to be very stressed and in decline. Various ideas were given as to why the trees were so different with an idea that the base of one tree had had additional soil or compost applied at the base.
After this we discussed Brambles in the use of veteran tree management. These act as a natural buffer to keep the public away from the base of the tree, this lessens compaction to the root plate and is also a risk management strategy to retain natural features, if they were to fall from the tree they would land in Bramble; Brambles are members of the Rosaceae plant family, these are a reliable source of nectar for emerging invertebrates from the decaying wood habitat which they can no longer feed on. Brambles also create their own mulch as they trap decaying matter on the ground.
The next stop was by two of the most interesting trees in the park to discuss; the first was a Beech tree with two ‘notorious’ decay fungi and the other was one of the most impressive Field Maples you will ever see! The Beech is a mature tree with a large Ganoderma australe bracket on the northern side and Meripilus giganteus annual brackets to the south; to many arborists and tree managers this is an instant sign that the tree should be felled. Yet here the tree still stands! Ted Green brought up the very interesting point that M. giganteus isn’t the pure parasite it is believed to be: within the trees canopy branches regularly die and remain in the tree, how do we know that this isn’t the case with the roots? How do we know that Meripilus is killing live roots and not decaying dead roots? We don’t know is the simple answer.
Meripilus has a reputation for resulting in windblown trees but is it the only cause? Is it simply finishing off a weakened and stressed tree? Again we don’t know, so as is always the case we have more questions than answers! Also with this tree there was a discussion on tree statics led by Kevin Martin from Kew Gardens, and for my part, this was one of the most interesting aspects of the visit. I also want to point out that this is a tree that we regularly monitor and inspect – we don’t get complacent about any of the trees.
The Field Maple is one of my three favourite trees in Kensington Gardens. This is a brilliant example of a veteran field maple which is around 18m tall at a guess. I posed the question that is this specimen is a ‘true native’ as compared to newer planted trees. If you look closely at the leaf structure it is very different from a nearby young field maple; my theory is that the younger field maple is possibly of European provenance where as the veteran maple predates a lot of the mass importations of the 20th Century. Issues regarding the management of this tree were discussed, then Ted Green told us the story of the Wild Service and why pubs are called Chequers due to the drink brewed from the berries, this was because there was a Wild Service nearby.
The next stop was along Lancaster Walk, the central London Plane avenue that runs through the centre of the park. Here we stopped at a group of Plane tree that did have mulch, this was due to it being part of a study group to identify cultural controls to alleviate Massaria Disease of Plane. This was a good opportunity to talk about the research projects that The Royal Parks are involved with, co-run with Nev Fay of Tree Works Environmental Practice; Nev spoke of soil health, the importance of our soils, the threats they face, the benefits of mulching and compost tea application and soil ecology. After this we briefly looked at an unfortunate example of dog damage to one of our young Sweet Chestnuts then we moved on to the last stops of the tour.
This was the second of my three favourite trees in the Gardens – a veteran Sweet Chestnut which is a full canopied tree solely from one functional unit of sapwood on a decaying old trunk. My poor description doesn’t do the tree justice but it is truly remarkable and was easily the most photographed tree of the day. At this point Neville Fay described the process of reiteration in veteran tree growth and Ted Green discussed Mildew of Oak. One question that I asked is how do you age a tree like this? Is it from when the tree first germinated? Arguably all of that part of the tree is dead, or do you age it from the reiterative growth? Or is it all from the same roots?
Finally, on to the last stop which were a group of Aesculus hippocastanum ‘Baumannii’ which are double flowering Horse Chestnuts where we briefly talked about soil amelioration before a closing address was delivered by Nev Fay, Ted Green, Jill Butler and ATF Chair Russell Miller. We then went to view the Elfin Oak and have a drink at the cafe, which was fortunate timing as it started raining!
Some of the suggestions made for veteran tree management in the park were increased mulching, more leaf retention, a change in mowing regimes around trees and the reintroduction of large mammal grazing in Kensington Gardens.
The next ATF London meeting is likely to be in the spring of 2018.