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) Page 27<br />
51. The lifespan of trees varies considerably <strong>and</strong> many species have shorter than average<br />
lifespans in <strong>the</strong> urban environment. Some like birch <strong>and</strong> cherry are relatively short-lived,<br />
with a typical lifespan of 50 to 80 years. O<strong>the</strong>rs, most notably oak <strong>and</strong> plane, have<br />
potential life spans of two centuries or more. Whilst it is possible to remove any tree, it is<br />
worth noting that <strong>the</strong> removal of older <strong>and</strong> large trees, even for reasons of safety, can<br />
be contentious.<br />
52. The age of trees is increasingly of relevance in <strong>the</strong> preservation of boulevard or avenue<br />
planting. Such planting has <strong>the</strong> best impact when trees are approximately <strong>the</strong> same<br />
size. Conversely, if many trees die in a small space of time <strong>the</strong>n <strong>the</strong> boulevard effect<br />
will be potentially lost for decades. Fortunately, <strong>Westminster</strong>’s stock of mature planes<br />
have 50 years or more of life remaining although it is likely that tough decisions on<br />
whe<strong>the</strong>r to pursue a balanced age structure will need to be made in <strong>the</strong> future.<br />
53. It is also worth noting that <strong>the</strong> shape of trees changes over time, depending on species.<br />
Young trees often exhibit strong characteristics of “apical dominance”, in that <strong>the</strong>y have<br />
a central leading shoot <strong>and</strong> a crown shape that is compact <strong>and</strong> narrow. As <strong>the</strong> tree<br />
matures <strong>the</strong> crowns of many species become broader, branches less upright, <strong>and</strong><br />
wider-spreading with <strong>the</strong> passage of time. It is <strong>the</strong>refore important that <strong>the</strong>se changes<br />
to shape <strong>and</strong> size over time, sometimes a very long time, are anticipated <strong>and</strong> factored<br />
into <strong>the</strong> design requirements <strong>and</strong> choice of species. Larger species that tolerate<br />
pruning are particularly valuable.