Tree-planting schemes are the most widely carried out form of habitat restoration. Native species are generally preferred, with the use of stock raised from local-provenance a relatively recent concern (Flora Locale 2001). As noted above, however, there is often remarkably little insight into either the aesthetic or the ecological aspects of woodland planting in the landscape. As Tregay notes, ‘room-like’ open spaces, such as glades, have been ‘very seldom developed in constructed parks of the last thirty years’ (Tregay and Gustavsson 1983). Tregay, working in an area of Warrington New Town in Lancashire, England, developed a sophisticated strategy for enhancing the aesthetic and ecological qualities of woodland.
Paramount was developing a sense of place by relating the new landscape to the site with the development of a diversity of microhabitats playing a major role, for example with narrow ‘fingers’ of planting penetrating into housing areas, ‘little more than broad free-growing hedges, widening in places to scrubby thickets, with an open canopy of light shade-casting trees’ (Tregay and Gustavsson 1983:25).
Tregay criticises the common run of tree planting where transplants are put in at even spacing, ‘resulting in a degree of uniformity rarely
A hot, dry site at the foot of old foundations is home to a variety of dry calcareous meadow species at
the Klenzepark in Ingolstadt,
Salvia nemorosa, Eryngium amethystinum (July)
seen in nature…the elements of surprise, fun, uniqueness, unpredictability and even weirdness, which can be seen in nature’ (Tregay and Gustavsson 1983:72). In order to overcome this, he proposes a variety of imaginative techniques: planting to create multistemmed trees, grouping of Corylus avellana whips to simulate old coppice, the massing of Fraxinus excelsior and Betula spp. to look like natural regeneration, the variation of plant spacing throughout the plantations, loose-edge planting at the edges, and the pegging of occasional transplants at angles to encourage variation in form (Tregay and Gustavsson 1983:73-74).
Crucial to the development of a genuinely naturalistic aesthetic and associated biodiversity is management, with varying densities of thinning, coppicing and the retention of interestingly shaped trees, the aim being the development of a rich variety of tree and shrub combinations, glades and a patchwork of differing light intensities at the forest floor level. Interestingly, Tregay discovered that randomly mixed tree plantings created problems of succession as early as the third year after planting. Extensive thinning was vital to preserve slower growing species, such as Quercus robur and Ilex aquifolium. The conclusion drawn was that the random mix was too dependent upon management, and that slower-growing species needed to be grouped within a matrix of nurse species (such as Alnusglutinosa and Betula spp.) (Tregay and Gustavsson 1983).
Gustavsson stresses the importance of creativity in woodland planting, and suggests the use of ‘dominating themes and sub-themes’ and ‘linkage’, so, for example, a walker through woodland might come across oak and lime, then notice a shift to oak and maple, and then oak and hornbeam. There should be an underlying feeling of uniformity, but this should be tempered by underlying variations and sub-themes in the species mix, ‘if you come 50 times you should still be able to still see new aspects, not just a tourist landscape’ (Gustavsson 2000). Gustavsson also does not exclude the use of some nonnative tree species included for ornamental reasons.
In ‘Det nya landskapet’, Gustavsson (1994) discusses a range of possibilities for the planting of woodland that offer options based on aesthetic, ecological and functional criteria. Woodland planted with shade-tolerant species in the centre and more lightdemanding ones on the outside ‘reinforces the centuries-old feeling that forests become denser the further into them one ventures’, yet is not particularly effective as screening or windbreak. More dense planting on the outside though ‘provides greater durability against outside forces’ and ‘provides an opportunity to include surprises’, and ‘gives the illusion of leaving the city behind’. He goes on to discuss zoning in forests to provide different areas for varying recreational, ecological or economic purposes. He recognises the importance of transition zones, and how they can be varied: from sharp to diffuse, with the latter useful for inducing a feeling of being in true countryside, whilst linking species can be used to play down the prominence of a boundary (Gustavsson 1994).
Gustavsson believes tree planting to be too dominated by the use of features that are immediately apparent in individual trees, such as leaf colour or bark texture. The architectural use of trees, and their articulation through space is limited to the thinking about their external appearance, ‘I want to stress how it is possible to articulate the interior of tree plantings’, he says, ‘the woodland concept has not been used much’ (Gustavsson 2002a). This, perhaps, is not surprising given how little the ground layer is considered in most treeplanting schemes.
It should be clear that management is a very creative process, indeed part of the design process. Gustavsson stresses how design should not be limited to the establishment phase, and that it is ‘a crucial part of good management’. As an illustration, he discusses how many urban woodlands in Europe are suffering from ‘teenager problems’, as there is a lack of ‘active and creative management’ (Gustavsson 2002b). He puts into words what many practitioners involved in tree planting feel all over the world, that trees are planted and then left with little aftercare, or if there is aftercare, it is purely technical.
There seems to be a general lack of what could be called a ‘holistic’ approach to large – scale tree planting (i. e. considering the whole woodland: trees and ground layer), with part of the problem possibly arising from the fact that it is difficult to install a ground layer that needs shade in a young forest that offers none. Andropogon, who do address the problem perhaps more comprehensively than any other practice, favour using a mix of tree sizes, including some semi-mature stock which does offer immediate shade. The costs, however, can be considerable. Carol Franklin stresses how ‘every square inch has to be filled’, otherwise invasive (often non-native) weeds will take over. The practice favour using native species that are aggressive but ‘well down the successional line’, for example Aster divaricatus, which will compete with invading weeds. In lower-budget projects, the practice favour covering the ground with leaf litter and twigs (which help mycorrhiza establish). ‘Critical islands’ of slower growing woodland floor species can be planted, which will then hopefully allow propagules to spread into all areas (Franklin 2002).