6
Medium to Tall
Invasive, Non-Native Trees
Norway Maple (
Acer
platanoides
) has large leaves
similar to sugar maple. Break a
leaf or stalk – a drop of white
sap will show if it is Norway
maple.
Fall foliage is yellow.
(Exceptions: cultivars such as
“Crimson King," which have red
leaves in spring or summer, may
have red autumn leaves.) The
leaves turn color late, usually in
November.
This tree suppresses growth
of grass, garden plants, and
forest understory beneath it, at
least as far as the drip-line.
Our mixed deciduous forests
will give way to pure stands of
Norway maple in the next
century unless we control its
spread now.
Control: (1); (7), (8), (9), or
(10); (11) in mid-October to early
November, before the leaves turn
color.
Tree of Heaven (
Ailanthus
altissima
), known from
A Tree
Grows in Brooklyn
, is incredibly
tough and can grow in the
poorest conditions.
It produces huge quantities of
wind-borne seeds, grows rapidly,
and secretes a toxin that kills
other plants. Once established,
this tree cannot be removed by
mechanical means alone.
Control: (1) – seedlings only.
Herbicide – use Garlon 3a(9)
with no more than a 1" gap
between cuts, or (10); plus (11) on
re-growth. Or paint bottom 12" of
bark with Garlon 4 (in February
or March to protect surrounding
plants). Use maximum strength
specified on label for all herbicide
applications on Ailanthus.
Glyphosate is not effective
against Ailanthus.
Sawtooth Oak (
Quercus
acutissima
) – often recommended
for wildlife, this Asian tree has
spread into our region from
forestry plants, displacing
indigenous forest trees.
Control: (1); (7), (8), (9), or (10);
(11) on small trees and re-growth.
This Guide was compiled for the Maryland Native Plant Society by
Louisa Thompson, Master Gardener Consultant, Maryland Cooperative
Extension, March, 1999.
Sources include:
s
“Exotic Plants," by Gene Cooley, MD Natural Heritage Program
s
“Invasive Alien Plant Species of Virginia," by the Virginia Native
Plant Society and the VA Division of Natural Heritage
s
“Plant Invaders of Parks and Natural Areas," by the NPCI Alien
Plant Working Group
s
“Invasive Exotic Pest Plants in Tennessee," by the Tennessee Exotic
Pest Plant Council
s
“Element Stewardship Abstracts" of The Nature Conservancy
s
“Invasive Plants: Weeds of the Global Garden," by John M. Randall
and Janet Marinelli, 1996, Brooklyn Botanic Gardens Book Club
s
The Monsanto web-page (
www
.monsanto
.com).
The author would like to thank Rod Simmons, Jil Swearingen, Susan
Rudy, Susan Salmons, Philip Pannill, Marc Imlay, Marion deGroff, Jane
Baldwin, Graham Egerton, and Ray Bosmans for their comments.
Control of invasive exotic plants is a new endeavor; the
recommendations given here may not have been fully tested.
Recommended Native Grasses
Native grasses usually grow in
small clumps, in a mix of several
species.
Tall ones include Indian grass
(
Sorghastrum nutans
), Big
bluestem (
Andropogon gerardii
),
Purple top (
Triodi flava
), and, on
the coastal plain, Switch grass
(
Panicum virgatum
).
Small to medium grasses
include Little bluestem
(
Schizachyrium scoparium
),
Bottlebrush (
Hystrix patula
),
and Wild oats (
Uniola latifolia
).
