Woodland edges
Woodland edge habitats offer a variety of ecological niches both spatially and over time. The addition of flowering perennials to the strip that abuts woodland is a feature that adds considerably to its aesthetic value, whilst the development of a ground layer amidst shrubby vegetation could make a considerable difference to the appearance of large areas of public green space. Native vegetation is sometimes used in Germany and the Netherlands in this situation, whilst in Britain occasional use is made of both native species and non-natives (Figure 3.6). Of the latter, forms of Geranium x oxonianum are the most widely used, its practically evergreen habit and vigorous nature making it ideal. In addition, its seasonal growth pattern, whereby stems tend to ‘collapse’ after flowering to be replaced by new growth from the centre, makes it ideal for literally smothering surrounding weedy vegetation. Its long season of growth makes it ideal for use in maritime climates with a long growing season.
Coppicing
One of the most creative styles of woodland edge habitat is potentially afforded by coppicing, whereby trees and shrubs are cut down to ground level on a regular basis. Traditional coppicing, as practised in northwest Europe, works on a cycle of around 25 years, with the ground-layer vegetation changing over this period from a combination of relatively short-lived herbaceous species, such as Digitalis purpurea and Silene dioicia in the early open stages of the coppice cycle to more shadetolerant species in the later, more closed, phase. The latter, for example Primula vulgaris, often survive the open phase and the late, very shady, phase of the coppice, but not making anything like optimal growth.
Nigel Dunnett has proposed that coppicing has great potential as a creative management tool for gardens and public green space, with areas cut on a rotation basis, resulting in ‘coppice shrubbery’. The foliage of many tree species is larger and more luxuriant in the years following ‘stooling’ or cutting back, whilst the pattern of microhabitats that develops on the ground creates the potential for the cultivation of a wide range of herbaceous species (Dunnett 1995:144). Dunnett has established an experimental plot at Harlow Carr Gardens (now RHS Harlow Carr) in Harrogate, Yorkshire, which has been running since 1997, using a mixture of native and non-native species.
