Goat Willow in the Arboretum
A lot of conservation work seems to involve the chopping down of things in order to maintain the habitat one is trying to preserve. In the arboretum the plan is to keep a lot of the flowering meadow with its native flowers not only to allow good views of the specimen trees, but also to help increase the biodiversity by providing more feeding niches for wildlife. The presence of goat willow causes a bit of a dilemma on the one hand it is very good for biodiversity, on the other hand it is an invasive pioneer tree species that can quickly grow and take over bare ground if not kept in check.
Being a native tree Salix caprea, the goat willow is ecologically an important species. Willow trees are dioecious, meaning that male and female flowers are found on separate trees. They are pollinated by insects and so secrete nectar. The flowering catkins are visited by Bumblebees, wasps, bees, hoverflies, beetles, moths and butterflies. Goat willow blossoms early in the year and has lots of flowers so is very valuable to these insects. For the honeybee it is the first mass forage source of the year. Bluetits have also been seen on the flowers consuming the protein rich pollen. Some of the moths and butterflies have the willow leaves as their caterpillar food source. In turn, the small birds that feed caterpillars to their chicks visit to collect them. Roe deer in the arboretum have also been seen browsing on the lower branches and any re-sprouting growth.
The goat willow is a native pioneer tree species found from southern Norway to eastern Spain and as far east as western Asia. Being a ‘pioneer’ tree it will quickly take root on any clear cut ground, grow very rapidly so initiating forest succession. The tree can propagate itself vegetatively, when a branch touches the ground it develops roots at that point and becomes a new tree. It also has many seeds every year that are dispersed by wind and water; therefore spreading far and wide.
When the arboretum was started initially half a dozen goat willow trees that had seeded themselves over the previous few years out in the main meadow were felled. Like most native trees when coppiced they re-sprout from the base sending up many slim spindly new shoots. In the first year the deer kept most of them in check by browsing. However last year was so wet the annual mowing could not be done and so many of these new stems had grown to over 2 metres tall. This is where conservation work has a role to play. In January the new willow stems were cut down to ground level by hand. While out there many more new clumps of willow which had grown from windblown seeds were found, these too were cut down. Hopefully the deer will enjoy eating the fresh young shoots that emerge. This work is not impacting the biodiversity as there are many large goat willow trees in the boundary hedges. The new southern hedge which was planted ten years ago also has goat willow in it. The ones that were cut down in the work party are too young to flower so it is hoped in this manner that the status quo of the flowering meadow can be maintained.