| The species chosen all exhibit characteristics associated with urban
suitability, good form, tolerance of harsh conditions. All tree plantings are
site specific and careful species selection represents a fundamental part of any
good urban forestry project. |
Rowan ( Sorbus aucuparia var.)
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Rowan can be slow to establish on exposed sites, however it grows well on clay soils and so is tolerant of the soil conditions in
London. A pioneer species it is a small to medium sized tree, a native with oval
crown and producing fruits much loved by wildlife. The variety Asplenifolia was
used in plantings last season, for it's unusual serrated leaf and it's fiery red
autumn colour and improved performance.
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Street tree suitability rating 5/10
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Field Maple ( Acer campestre Var. )
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Acer campestre Elsrijk |
Very tolerant of the urban environment in terms of climate and soil conditions.
Only native maple to the British Isles, Acer campestre is a tree with many
virtues, not least it’s show of bright yellow in Autumn and lobed leaves.
Fastigiate hybrids are now sold for street tree planting.
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Street Tree suitability rating 9/10
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Hornbeam ( Carpinus betulus )
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Fastigiate Hornbeam planted outside Globe Road Primary
School |
The same Hornbeams after 6 years
growth |
Fantastic architectural form, foliage can ‘burn’ ( become desiccated ) on
exposed sites, it is a tough tree tolerating pollution and compacted soils.
Considered indigenous to the south of England and once prevalent in the forests
that surrounded London, many examples can still be seen in Epping Forest. The
fastigiate form makes for an attractive street tree, being densely foliated. It bears fruits which
in no way resemble those borne by any other British tree, they grow in clusters
and hang in long tassels. If you have the space ( 10m for its crown ) then the
singular species is magnificent, best examples are Golden Square W1.
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Street tree suitability rating 7/10
Cherry (Prunus Ssp.)
Historically one of the most planted street trees. Unfortunately it's spreading habit and greedy surface roots cause problems in the Highway. In response nurseries have produced many fastigiate forms which pale in comparison to Prunus avium or padus, two great trees for open spaces. Of all prunus species subhirtella is probably bet suited to a street situation having a small medium canopy and flowers in winter.
Street tree suitability rating 4/10
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Birch (Betula Ssp.)
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| Steady growing, the Birch tolerates a wide range of conditions, it is a hardy
tree widespread in parks and along roadsides. There are around 40 species of
Birch, which can most easily be recognized by their bark and light foliage.
Little or no pruning required. Birch species will grow where the soil is poor
and thin, however does need weekly irrigation for first 1 -2 years and when
young can be ‘whipped’ by the wind if planted in locations where the wind is
strong, this can lead to problems with form. Interest provided by the bark year
round, when in leaf it sways gently in the breeze and in autumn can provide a
beautiful display of light yellow leaves. |
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Street Tree suitability rating 8/10
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Hawthorne
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| This tree is infrequently planted as it is slow growing and takes time to
find form , if used at all it is probably worth planting larger stock. Small
native tree, fragrant flowers in May, excellent for wildlife. It is not invasive
and it's adaptability has given rise to around 35 different species of Hawthorn
which flourish in a range of soils. |
Street Tree suitability rating 4/10
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Alder (Alnus SSp.)
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Alnus spaethii planted in the road |
Quick to establish, related to the birch, the Alder is a hardy tree and
disease resistant, however, like many trees it does suffer from sudden death
syndrome. Alders grow in symbiosis with certain bacteria (Actinomycetes) which
absorb Nitrogen from the air. These organisms live in the roots and their
presence actively improves soil fertility. It is a medium tree ( 20 Metres at
maturity ) and the species Spaethii produces a magnificent show of 6in long
catkins in the winter months. Can be prone to problems with form i.e. forking of
the leader,
also known for its speed of growth which should be taken into account when planting on narrow roads and streets
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Street tree suitability 6/10
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Chanticleer Pear (Pyrus calleryana ‘chanticleer’ )
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First planted in Westminster 25 years ago this new species was also planted
on Oxford street in the mid nineties and like the ‘plane’ is tolerant of
pollution. Able to cope with of harsh conditions both wet and dry, a superb tree
for planting in the highway, it is even tolerant of salt. Although regarded as
unadventurous by some it is a tree that is reliable and will do well in
difficult locations. It is fast growing, oval in form, a medium-sized tree
producing pure white blossom, a tree of considerable merit with attractive
orange and red foliage in the autumn, however as with other trees, this flush is not always vivid in trees planted in streets due to poor soil conditions and other associatesd stresses caused in urban environments ( compaction, dessication etc ).
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Street tree suitability rating 9/10
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Dawn Redwood (Metasequia glyptostroboides )
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Good examples of Dawn Redwood are on Regency St and Kinnerton St SW1. A
deciduous conifer the species was not discovered alive until 1941 since which
time it has increasingly been used as a street tree in North America. Although
non-native the Redwood is praised for it's attractive conical form and is
regarded as a clean tree producing negligible leaf litter. Can require
irrigation for several years and likes moist soil conditions. Works well for
avenue planting where space is an issue
Street tree suitability rating 8/10 |
London Plane (Platanus x Hispanica)
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This non native hybrid probably reaches 10 metres after 15 years and is
therefore one of the fastest growing species and is akin to Eucalyptus species
for growth rates. It is a cross between European and North American Planes and
is thought to climax between 2-300 years. This tree is an iconic tree for London
hence the name and was widely planted, by the Victorians.
Attractive bark when mature although cannot rival the single species plane
trees. Recently plane varieties have been grown on as cultivars with the
cuttings taken from trees growing in London’s Squares. e.g. Platanus x hispanica
‘Portland’
One drawback is their contribution to Suspended Particulate Matter when hairs
are distributed into the atmosphere as they shed their sterile seed in spring
and summer. Furthermore, although majestic in the correct location when allowed
to approach it’s true spreading form this large tree has been over-planted and
as a result, can be seen growing up against buildings and blocking light etc
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Street tree suitability 6/10
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Broad leaved Privet (Ligustrum lucidum)
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Chinese Privet planted 5 years ago |
This non native from China has a very vigorous habit smaller than many trees only reaching 10-15 Metres. It may be regarded by some as a ‘lollipop’, however it is functional and thrives in tough urban condition
It has an excellent semi evergreen crown that only takes a few years to give a
good rounded canopy and requires little maintenance although an allowance must be made for canopy as it is dense and can block light. Some good examples are at
the north end of Hatton Garden.
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Street Tree suitability 8/10
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Alternatives
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The above list is by no means exhaustive and may be regarded as
unadventurous, however when dealing with plantings in the highways it is
necessary to consider issues of liability and reliability. The trees mentioned
are functional and their characteristics are well known and many are native
which for some is a key consideration.
However in recent years local authorities have trialled other species whether
for reasons of site conditions, anticipated changes in climate patterns or
novelty, to change the aesthetic of the street environment. It is no longer rare
to see Photinia, Ginkgo, or Magnolia planted in the street and the list
continues to grow.
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