Introduced Species Summary
Norway maple (Acer platanoides)
Common Name: Norway
Scientific Name: Acer platanoides
broad, rounded crown that is densely limbed. The bark begins smooth and grayish, but later becomes darker and narrowly and vertically fissured. The leaves are opposite and can be very large, up to 7” both long and wide and are palmately veined and notched with 5 distinct lobes. The top surface is a dull green, and the underside is hairless, glossy and pale. They turn bright yellow in autumn. The leaf stalk is long and narrow and produces a milky sap when broken at the end. Flowers are bright green, 5/16” wide, with 5 upright petals clusters which occur just before leaf out. Fruit is 2 “helicopter blades”, or samaras, each about 1-2” long that contain a seed in the middle. The samaras mature by the end of summer and are dispersed by the wind. It is possible that some seeds are eaten and dispersed by birds and small mammals as well. Buds are very large, much larger than the buds of sugar and red maples ( Acer saccharum & Acer rubrum ). They are glabrous,
stocky and usually turn green to red with large scales surrounding. The terminal bud is especially large and is an easy indentifier from native maples in the winter (but not to be confused with the sycamore maple, Acer psuedoplatanus, another invasive species, which has a large terminal bud that remains green).
Acer is the name for maples within the family Aceraceae and platanoides means “like platanus”, or like the sycamore because its leaves resemble that tree. It is, however, not related to it.
In addition to its native range, the Norway maple is widely planted in the
Site and Date of Introduction:
The Norway maple was first introduced to
Mode(s) of Introduction:
It reached the East Coast, and later the West Coast by ship sailing from
Reason(s) Why it has Become Established: The
All of these factors have led up to the Norway maple easily escaping cultivation and spreading out into fields, edge habitats, disrupted habitats, and mature forests. It quickly shades out other tree, shrub and herbaceous species and establishes itself as the primary canopy cover. Since its seedlings and saplings grow well in the shade of the bigger seed-source tree, it forms monotypic stands that perpetually expand.
Ecological Role: The Norway maple is predominately a shade tree, and even in a dense canopy
tends to retain a relatively
expansive crown. As a pioneer species,
in its natural habitat for shade tolerant second-succession conifers, such as hemlocks. Also, as mentioned, its seeds can be eaten by birds and small mammals. In lean acorn years, squirrels and porcupines might also strip away the bark to gnaw on the cambium layer (provided there are no sugar or red maples nearby, both of which provide a tastier and more copious sap).
Benefit(s): The Norway maple seems to offer little commercial benefit other than firewood. As a strong fairer in unhealthy soils, it creates important root structures on nutrient poor soils found on steep slopes that would otherwise be prone to erosion. Its primary function in cultivation has been as an ornamental shade tree. It is very tolerant of temperature extremes and so performs well in open, hot areas such as lawns, municipal parks and along streets. They grow quickly and without much care so one can occupy a newly landscaped area as a large tree in little time. They also provide an aesthetic function in towns and cities as they turn bright yellow in autumn.
The greatest threat the Norway maple presents to
Once it has established itself as the dominant canopy species, the Norway maple works to both vigorously propagate its own seedlings and shade out other species seedlings. In a study done by Peter Wyckoff and Sara Webb of Drew University, it was determined that even the sugar maple (Acer saccharum) and American beech (Fagus grandifolia), which are the only two canopy species in the northeast U.S. that are not shaded out by the Norway maple as they reach for the canopy, did not fair well as seedlings under a Norway maple canopy. Yet under the same canopy Norway maple seedlings comprised up to 98% of all seedlings found. Therefore, the Norway maple monotypic culture not only spreads quickly, but is established quickly.
The Norway maple is also a primary host to the Asian longhorn beetle (Anoplophora glabripennis). This is a large insect that lays its eggs within the bark of the tree. The larvae then tunnel into the wood and create extensive galleries within the heartwood and cambium. This creates great damage to the trees’
structure and nutrient flow. Adults then chew their way out to infest other nearby trees. The Asian longhorn beetle is fast becoming a danger to eastern hardwood forests.
The steady take-over of many
natural forests in the
almost impossible proportions
since the tree has become so abundant in natural areas already. The continued planting of the
tree, both on private and public lands, and the continued offering of it
Control Level Diagnosis: The control of the Norway maple is of the highest priority. Complete eradication seems unlikely but immediate control will at least slow its rapid spread and give forests that are already infested with it a chance to recover while there are still other species present in those forests to help in such an effort.
Control Method: Methods of removing or halting the growth of the Norway maple vary and can be determined by the severity of the infestation, the type of environment they are found in, and resources available. Preventative control should also not be overlooked for land managers seeking to plant large, hardy, shade-bearing trees.
However, if the same stand
Herbicides are effective in
speeding up the killing process by applying to both cut stumps and girdled
trees. Tryclopyrs and glyphosate agents are readily available and effective.
Group of the New York City Parks Department. This method also keeps the dead tree in place.
If only seedlings and saplings
require removing, hand weeding may be the only process needed. A weed wrench, which is a long-handled
device that grips a sapling at its base, uses leverage to pull
Finally, the best thing landscapers
and developers can do in this effort is: do not plant
Gargiullo, Dr. Margaret B., Plants of New York City Natural Areas, NYC Parks, Natural Resources Group, 2002
Little, Elbert L. , The Audubon
Society Field Guide to North American Trees, Alfred A. Knopf, New
Swearingen, J.,K. Reshetiloff,
Webb, Sara L., T.H. Pendergast IV, M.E. Dwyer, “ Response of native and exotic maple seedlings banks to removal of the exotic, invasive Norway maple (Acer platanoides)”, Journal of the Torrey Botanical Society, 128(2), 2001, pp. 141-149
Forestry team of the Natural
Natural Resources team,
Photo from: http://oregonstate.edu/dept/ldplants/acpl1.htm
Author: Rich Love
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