Trees and the Public Realm - Westminster City Council

Trees and the Public Realm (Draft) Page 39
97. Where there is greater abundance of space it is important to understand the function,
constraints and opportunities of the place, and choose a tree that is of a size and form
that complements it. If appropriate a single large, impressive ‘landmark tree’ can be
the preferred option.
Canopy Density
98. Once a tree of appropriate size and canopy shape has been selected there are other
characteristics needing consideration such as leaf size and shape, flowering and
ornamental bark. Perhaps the most important of these is the density of the canopy or
the arrangement of the branches. Broad-canopied trees with low spreading branches
will create proportionally larger areas of shadow than will a narrow-crowned tree, which
can be a positive characteristic in casting shade in the day.
99. ‘Open canopy’ trees such as birch and false acacia possess relatively small leaves that
are carried on well-spaced branches. The result is a canopy that is partially transparent,
allowing dappled light to filter through. They have a lightness about them that, even in
large specimens, is not oppressive. ‘Closed canopy’ trees tend to have closer
branching and larger leaves. Trees such as horse chestnut and whitebeam have fully
opaque canopies that cast dense shade. They are good for screening but in some
environments they can create a somewhat gloomy atmosphere, and can block views
and affect the micro-climate.
Blandford Street, W1 (left) and Gloucester Place, W1 (right): The beautiful bark, light and well shaped canopy, and
moderate size of the silver birch in Blandford Street makes it an effective street tree whilst the sparser canopy of
this particular Gingko is less attractive and does not complement the architecture or streetscape in this instance.