LOW-MAINTENANCE STREET TREE CULTIVARS
What does that mean?
- A "cultivar" is a cultivated variety of a species. It is reproduced
from a single individual in such a way (usually asexual propagation) that
traits can be kept.
- A low-maintenance street tree cultivar is one that has been
selected for superior traits and that will increase safety and/or lower maintenance
costs.
- You can recognize a cultivar by the extra words that are added
to the species name. E.g., Crimson King Norway maple (Acer platanoides
‘Crimson King’).
What is important to know about them?
- Cultivars are predictably better than the species in some way (shape,
color, pest resistance, etc.).
- Cultivar populations--where all individuals have the identical
genetic makup--are less adaptable to change than species populations.
- Cultivars on their own rootstock are usually preferable to those
that have been grafted.
What are some good cultivars for urban use?
- Trees need to be selected for particular sites and uses, so there
is no such thing as a general list that can work for everybody.
- Here are some street tree cultivars that tolerate difficult urban
conditions in the NE United States (pH 7-8, full sun, USDA Zone 4, dry and
somewhat compacted soil):
Autumn Blaze hybrid maple (Acer x freemanii ‘Jeffersred’).
Combines the fall leaf color of red maple with the urban soil tolerance
of silver maple.
Greencolumn black maple (Acer nigrum ‘Greencolumn’). A narrower,
hardier and more drought tolerant cousin of sugar maple, with the same
fall color.
Prairie Pride hackberry (Celtis occidentalis ‘Prairie Pride’).
Selected for strong central leader and resistance to disfiguration by insects.
Patmore green ash (Fraxinus pennsylvanica ‘Patmore’). Seedless,
very cold hardy, and excellent branch structure.
Princeton Sentry ginkgo (Ginkgo biloba ‘Princeton Sentry’).
Fruitless male tree, very tolerant of urban conditions, narrower than the
species.
Skyline honey locust (Gleditsia triacanthos inermis ‘Skycole’).
Strong central leader, easy to raise for clearance, somewhat more resistant
to insects.
Macho Amur cork (Phellodendron amurense ‘Macho’). Upright
habit, smaller stature, and no seeds.
Autumn blaze maple
(Source: http://www.dawesarb.org/images/Acerfreemaniiautumnblaze_fall.jpg)
- Some of them are available at good regional nurseries, so
call and ask.
- Otherwise, order (6 months ahead of time) from the catalogue of
a wholesale nursery, preferably one noted for quality stock that has been
planted out under climate and pest conditions similar to yours.
Where can I get more information?
Gerhold, Henry, et al. 2002. Landscape Tree Factsheets.
University Park PA: Penn State Press. Excellent photos and descriptions
of many cultivars. For other information, advice and help on this topic,
call offices of your State Urban Forestry Coordinator or University Extension
service, visit urban forestry web sites.