Maine
Tree Species Fact Sheet
 Common
Name:
Black
Locust (Yellow Locust)
Botanical
Name:
Robinia pseudoacacia
Tree
Type: Deciduous
Physical
Description:
Growth Habit:
Black locust is a rapidly growing tree that grows naturally on a wide
range of sites but does best on rich moist limestone soils. It has the
ability to fix nitrogen and in this way partially creates its own
nitrogen supply. The branches are small, brittle, occasionally
multi-angled, and when young have short stiff spines in pairs at the
base of leaves. It is one of the last trees to send out foliage in the
spring. The bark is rough, yellowish brown in color becoming deeply
furrowed into distinct, thick, rounded ridges, which are not scaly. The
leaves are alternate, compound, from 8 to 14 inches long, with 7 to 19
entire leaflets arranged along a central stem. The leaflets are usually
odd in number, short-stalked, oval in shape and from 1 1/2 to 2 inches
long.
Height:
Black locust reaches a height of about 50 feet and a trunk diameter of
8-20 inches.
Shape: Black
locust is often an upright tree with a straight trunk and a narrow
oblong crown, which becomes ragged and scraggly with age. It will
develop thickets as it freely seeds, and develops shoots from roots.
Some forms of this tree have a spreading habit with several trunks.
Fruit/Seed
Description/Dispersal Methods:
The fragrant,
whitish flowers, borne in showy racemes, appear after leaf emergence.
The perfect flowers originate in the axils of the current year’s leaves
and are pollinated by insects, primarily bees. The fruit is a
flattened, oblong, 2-4 inch, smooth brown-black pod that ripens in the
fall and contains 1-8 beanlike seeds. The fruit opens on the tree and
seeds are dispersed from September to April. Black locust begins seed
production at about six years of age.
Range within
Maine:
Black locust is
not a native to the state of Maine, but it is extensively planted. It
is abundant in some localities and is found mostly near dwellings or on
abandoned farmlands, where it often becomes naturalized. This tree is
hardy in Zones 4-8.
Distinguishing
Features:
The black locust
has compound leaves with oval leaflets and small downy buds that are
depressed in the bark. It also has short stiff spines and papery seed
pods.
Interesting
Features:
Although black
locust is not an important timber tree in the United States, it is used
for a wide variety of products and is planted for many specialized
purposes. The wood is heavy close-grained, strong and very durable. It
is used for fence posts, poles, railroad ties, ship timber, tree nails
for wooden ship construction, boxes, crates and stakes. It is said by
some native New Englanders to last “3 years longer than a stone wall.”
The flowers are
exceedingly fragrant and the bees produce honey from them.
Relationship to
Wildlife:
Black locust
provides cover for wildlife, browse for deer, and cavities for birds.
Landscape Use:
Black locust is
not recommended for home landscapes. It is a good tree for highway cuts
and fills, sandy and poor soils. It is a species that can survive in
the toughest of conditions.
Common Problems
or Pests of the Tree in Maine:
Canker,
dampening-off, leaf spots, powdery mildews, wood decay, witches’ broom,
locust borer, carpetworm, locust leaf miner, locust twig borer, and
scales affect Black locust. The most destructive pest is the locust
borer, which can riddle whole trees.
References:
Forest Trees of
Maine, Twelfth Edition.
Maine Forest Service/Department of Conservation. 1995.
Know
Your Trees. Cope, J.A. and
Fred E. Winch, Jr. Cornell Cooperative Extension. 1992.
Manual of Woody
Landscape Plants, 5th Edition.
Dirr, Michael A. Publishing L.L.C.
1998.
United
States Dept. of Agriculture: Silvics of North America
http://www.na.fs.fed.us/spfo/pubs/silvics_manual/volume_2/robinia/pseudoacacia.htm
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