Trees and the Public Realm - Westminster City Council
Trees and the Public Realm - Westminster City Council
Trees and the Public Realm - Westminster City Council
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<strong>Trees</strong> <strong>and</strong> <strong>the</strong> <strong>Public</strong> <strong>Realm</strong> (Draft) Appendix D - 1<br />
APPENDIX D<br />
COMMONLY USED SPECIES IN WESTMINSTER<br />
Choice of species is crucial to <strong>the</strong> provision of a healthy tree that is appropriate to both a local sense of place<br />
<strong>and</strong> its intended function, with space to grow to maturity with minimal intervention or management. <strong>Council</strong>’s<br />
arboriculturalists are best placed to advise on what species are appropriate however <strong>the</strong>re are also a number<br />
of sources which can provide information in this respect. These sources include specialist publications,<br />
private nursery catalogues <strong>and</strong> also some good websites such as <strong>the</strong> following:<br />
• Greater London Authority, Right <strong>Trees</strong> for a Changing Climate.<br />
http://www.right-trees.org.uk<br />
• Royal Horticultural Society<br />
http://www.rhs.org.uk/databases/summary.asp<br />
To illustrate some of <strong>the</strong> considerations associated with tree selection, a selection of some of <strong>the</strong> most<br />
common trees used in <strong>Westminster</strong> are listed below. These species have varying relationships with<br />
environment (in particular air quality) which needs to be carefully considered in relation to <strong>the</strong> nature of <strong>the</strong><br />
site <strong>and</strong> surrounds 1 .<br />
Large round trees (over 15m, height <strong>and</strong> spread approximately equal)<br />
► Norway Maple (Acer Platanoides)<br />
Sturdy tree of large proportions forming thick rounded crown with widely spaced branches. Suitable for<br />
parks <strong>and</strong> wide avenues. This species is not sensitive to nitrogen oxides <strong>and</strong> is very effective in absorbing<br />
<strong>the</strong>m.<br />
► Common Ash (Fraxinus excelsior) <br />
A native with a wide to oval shaped crown. It is suitable for parks <strong>and</strong> wide avenues <strong>and</strong>, if given <strong>the</strong><br />
room to grow <strong>and</strong> spread, <strong>the</strong> common ash forms a very striking specimen tree. Since <strong>the</strong>y need plenty<br />
of light, <strong>the</strong>y can easily be crowded out by o<strong>the</strong>r overshadowing trees. This species is particularly<br />
effective for reducing ozone concentration in urban areas.<br />
► London Plane (Platanus x hispanica)<br />
In addition to being fast-growing, <strong>the</strong> London Place is very tolerant of hard surfaces, vigorous pruning,<br />
atmospheric pollution <strong>and</strong> root compaction. For <strong>the</strong>se reasons it is a popular urban tree, however it does<br />
have some drawbacks in an urban setting – most notably <strong>the</strong> hairs shed by <strong>the</strong> young leaves <strong>and</strong> <strong>the</strong><br />
dispersing seeds in spring which can both be an irritant if brea<strong>the</strong>d in. The large leaves are also tough<br />
<strong>and</strong> can create a disposal problem. Fur<strong>the</strong>rmore, like some o<strong>the</strong>r large, broad-leaved species London<br />
Planes can potentially contain pollutants from traffic – particularly as <strong>the</strong>ir growth can tend towards <strong>the</strong><br />
centre of <strong>the</strong> road.<br />
The <strong>Council</strong> recognises that, given its mature size, <strong>the</strong> London Plane is best suited to parks <strong>and</strong> broad<br />
streets where avenues will have replacements of <strong>the</strong> same species. In o<strong>the</strong>r more domestic scaled<br />
streets it can ei<strong>the</strong>r grow too large for its setting or has to be heavily pollarded in order to remain without<br />
causing problems for buildings in close proximity.<br />
► Small leaved lime (Tilia cordata) <br />
A native to British Isles <strong>and</strong> large parts of Europe. Slow growing but produces large rounded canopy.<br />
Long-lived. Tolerant of most soils <strong>and</strong> hard surfaces. Suitable for parks <strong>and</strong> woodl<strong>and</strong>s. Many cultivars<br />
available with compact pyramidal shaped crowns suitable for street planting.<br />
1 Many of <strong>the</strong> details on <strong>the</strong> trees interaction with air quality in this appendix have been sourced from Plant <strong>Public</strong>ity Holl<strong>and</strong>, 2008.