Pollarding at Slimbridge

I was recently able to accept a long-standing offer to visit the Wildfowl and Wetlands Trust Head quarters at Slimbridge in Gloucestershire. The offer, made at the SALTEX show last year by Julian Edmondson, the Horticultural Manager at Slimbridge, invited me to see their pollarded willows and to highlight their 60th anniversary. I was told that they were doing some interesting things with them. I was not disappointed!

The Willow family must be one of the most maligned of our native tree species. Blamed for all manner of ills, from sucking up too much water to directly causing subsidence in buildings with its searching and invasive root system, the willow gets invariably bad press. In fact, in the right situation and with appropriate maintenance willows can provide an extraordinary landscape feature with year round interest – as I was about to find out. The first clue to what I was about to see came as I was approaching Slimbridge. I had to cross the canal, both banks of which were lined with old pollarded willows. The trees were almost certainly crack willow, with possibly some white willow - I couldn’t be sure. All had been pollarded over many years and displayed the classic features a wide short squat trunk, crowned by a bole and a profusion of wands. Is my guess that these trees had been planted around the time that the canal came into use. The use of willows for bank stabilisation in this area is very common - indeed it is not unusual to see willow used in this way down in the Somerset levels and it is a traditional feature of many marginal areas and flood plains. The trees readiness to strike from wands, and in fact almost any form of cutting means that has been an extremely cheap and easy method to stabilise Canal and River banks in addition to the added benefit of the crop of wands which can be used for a variety of tasks such as basket making, hurdles and faggots. It is these features that make the willows so useful to the horticultural team and Slimbridge.



The use of willows around the reserve was initially an act of necessity. When the trust was formed in 1946, it possessed understandably limited funds. Sir Peter Scott used the materials that were already abundant to create the walkways around the reserve and pens in the now extensive wildlife collection area. These took the form of post and rail fencing constructed of willow poles. A high proportion of these poles rooted and became the pollards that now give the site its unique character. These waist-high willows had to be cut back of course and the result is a forest of pollards scattered across the reserve, giving a blaze of colour - even on an overcast winters day. I was lucky to be able to enjoy some bright weather on my visit and was suitably impressed by the effect that these almost accidental trees have on the area. But don’t be fooled into thinking that all the trees here are of a uniform, rigidly maintained style. The horticultural team work hard to ensure that the willows are of constant interest and of value to the reserve and its most important visitors –the birds! Although the most obvious willows on the site are the pollards, there are some significant areas of coppice. These provide cover for nesting birds most notably wildfowl species and provide an ideal habitat for water voles. The area in which the reserve is situated is known to have willow coppice on it for hundreds of years and is shown on old maps. These ‘withy beds’ were delineated by pollarded trees that are still in evidence, although the withy beds have largely disappeared. Whilst the age of these trees, which are nearly always Salix fragilis, the Crack Willow, is almost impossible to gauge with any accuracy, it can be safely assumed that they are in the region of 250 years old.

In addition to the examples of the crack and white willow Slimbridge also boasts an eclectic mix of willow varieties, cultivars and hybrids - both native and non-native. There were plenty of Salix alba cultivars growing as pollards. Salix alba chermesina, with a strong orange hue provided a riot of colour which was particularly evident when the site was viewed from the observation tower, interspersed with less common examples of Salix alba vitellina - the golden willow, and the deep red almost purple stems of salix alba x rubens.

All these specimens were generally pollarded at approximately 3 or 6 feet depending in their location. The shorter specimens being those that had started life as the original fence posts around the reserve. Cutting is on a one-three year rotation to encourage the brighter colour found on the young growth. Other willows are found on site-S.nigricans showing black stems. Some of the traditional willow varieties for basketry are also present on site. S. viminalis or Oesier and S. Purpurea the Purple willow are grown as coppiced stands. S. cinerea, commonly known as grey sallow is kept as a low growing shrub rather than a true pollard and provides a breeding habitat for the Lunar Hornet Moth Sesia bembeciformis.
The 100 acres or so of the grounds at Slimbridge are maintained by a staff of four, with the reserve of some 750 acres being managed by an additional 3 staff. Both are assisted by an irregular complement of volunteers. Between 200 and 250 individual trees are pollarded every year, with those bordering the paths and walkways pruned on a yearly basis. The other specimens are on a bi-annual rota so as to preserve colour. Almost all of the pollarding carried out on the site is by chainsaw with about 5% of the work being done with bow saws – usually when the tree is in an awkward location. Richard Smith and Sarah Revill carry out most of the cutting in the grounds, with the reserve pollards cut mainly by Martin McGill. A number of staff are qualified as arborists at Slimbridge. The prospect of a large amount of major aerial tree works in the future will mean training up additional people as it will prove cost effective to keep the work in-house.

The arisings generated from the pollarding are put to a variety of uses around the reserve. Slimbridge tries to be as sustainable a site as it can and as such as much of its ‘waste ‘ as possible is used around the site.

A new composting facility has been established and aims to speed up the turnaround of green waste on-site. The material that is generated by the willow pollarding is not always composted though. All around the site willow had been used to provide screens and fences, living sculpture features and in specific locations was being placed into horizontal rows as a habitat for small mammals and insects. (see below)
The poles that are produced from the older pollards are used to create instant pollards, either to replace dead trees at Slimbridge or to establish new plantings at other wwt centres.



These poles, at between 6 and 8 feet in length, will simply be put into the ground and take their first pollarding in twelve months time.