In creating a new urban greenspace, the choice of tree species is central to the type of greenspace it will become. This choice will be affected by many factors, including:
- Type and species composition of neighbouring woodland
- Landscape design criteria for the greenspace
- Community and/or interest groups’ likes or dislikes
- Biodiversity aspirations
- Engineering or other constraints.
To ensure that trees will flourish, species choice must match the sites and soil characteristics. Soil resources are the most important determinant of which species are preferential during early establishment (the first 5–10 years), and into maturity, and should be considered when preparing a new site.
Trees that are properly tended on suitable sites can be expected to live for many decades, it is important to consider the type and appearance of the mature woodland or blocks of trees, and to plan for maintenance or management as a consequence. For example, broadleaved woodland may require provision of management of fallen leaves in autumn; mixed-species woodland may require selective thinning during the first 10–20 years; pruning may be required to facilitate public access. Likely final tree height may be an important consideration where the site is crossed by aerial cables, and likely rooting depth may be an issue if the site is capped, for example to contain contamination or landfill.
The longevity of trees means that likely future climatic conditions should be taken into account when choosing suitable species. For example, in south-east England the increasing likelihood of low summer rainfall should influence choice of more drought-tolerant species, and possibly of greenspace containing a wider range of tree species in order to reduce risk of widespread tree failure.
Edaphic requirements for individual tree species can be found by reference to standard texts or web-based resources, notably those focusing on soil acidity and water status (e.g. Moffat, 2006; the Mayor of London’s Right Trees for a Changing Climate).
Other factors to consider include tolerance to atmospheric pollution and salt (e.g. road salt). Growth habits can also be found in similar media. In the light of climate change scenarios, published by the UK Climate Impacts Programme, the Forestry Commission have produced species suitability maps. Professional advisory services may be useful for information on silvicultural care and management, especially in the case of woodland composed of species mixtures.
Forest Research has been conducting research on tree species suitability in the context of urban regeneration for several decades, and continues to do so. For example, guidance on Woodland Establishment on Landfill Sites has recently been published on the Communities and Local Government website. We are currently carrying out research on species choice for sites affected by contamination.
Forest Research offers site-specific advice on woodland design for greenspace projects, and has been a strong supporter of community forestry. If data on soil characteristics are unavailable, Forest Research can conduct an appropriate site survey, and its laboratories are designed to provide relevant information.
Forest Research Best Practice Guidance
Moffat, A. (2006). Native and Non-Native Trees: Why and How to Choose (PDF-1264K). Best Practice Guidance for Land Regeneration, BPG Note 8. Forest Research, Farnham.
Moffat, A.J. and McNeill, J.D. (1994). Reclaiming Disturbed Land for Forestry. Forestry Commission Bulletin 110. HMSO, London.