COMMON NAME

Black locust
False acacia
Yellow locust


FULL SCIENTIFIC NAME

Robinia pseudoacacia L.


FAMILY NAME COMMON

Pea family


FAMILY SCIENTIFIC NAME

Robinia pseudoacacia


IMAGES


Habit

Flowers

Bark

Flowers on Branch

Stipular Spines

Fruits

Clonal Growth

Flowers Close-up

NOMENCLATURE/SYNONYMS

Synonyms: Robinia pseudoacacia var. rectissima (L.) Raber


DESCRIPTION

Robinia pseudoacacia is a fast-growing tree that can reach up to 30.5 m (100 ft.) in height. The roots have nitrogen-fixing nodules. The trunk diameter can reach up to 1 m (3.5 ft.). The bark of the tree is gray to dark brown in color is deeply furrowed. The twigs of the tree have paired stipules that are modified into spines up to 1.5 cm (0.6 in.) long at each leaf. The bluish-green leaves are alternate and odd-pinnately compound, with leaflets occurring in pairs except for the terminal leaflet. These leaves measure 20-35.5 cm (8-14 in.) long. There are 7-19 oval leaflets that are each 2.5-5.0 cm (1-2 in.) in length. The margins of the leaflets are entire, and the leaves turn yellow-green in the fall. The leaves of Robinia pseudoacacia drop early in the fall. Leaf miners often attack the trees turning all of the leaves brown prematurely. The flowers of Robinia pseudoacacia are showy and fragrant. The white flowers with yellow centers are in dense racemes that can be 18-25 cm (7-10 in.) long. The calyces can be either red or green in color. The fruits are brown, flat pods that are glabrous and 5-10 cm (2-4 in.) long. Each of these pods contains 4-8 seeds that are reddish to brown in color. The pods develop from September to October and often remain on the tree well into the winter. Page References Bailey 560, Fernald 902, Gleason & Cronquist 280, Holmgren 262, Magee & Ahles 651. See reference section below for full citations.


SIMILAR SPECIES

Gleditsia triacanthos L. (honey locust) Gleditsia triacanthos leaves can be either pinnate (like Robinia pseudoacacia) or bipinnate. Gleditsia triacanthos also has much larger spines than R. pseudoacacia. The flowers of G. triancanthos are yellow-green and smaller, and its pods are long and twisted as opposed to the straight pods of R. pseudoacacia.


REPRODUCTIVE/DISPERSAL MECHANISMS

This tree mostly spreads by vegetative root suckers, though it can also spread via mechanical dispersal of its seeds.


DISTRIBUTION

Robinia pseudoacacia is native to the Appalachian Mountains from central Pennsylvania to northern Alabama and Georgia. It is also native to the Ozark Mountains of southern Missouri, north and west central Arkansas and eastern Oklahoma. It has been planted and naturalized as far north as Nova Scotia and in all the contiguous United States. It has become extensively naturalized in Europe as well as other areas where it has been introduced into cultivation.


HISTORY OF INTRODUCTION IN NEW ENGLAND

Even though Robinia pseudoacacia is native in the United States, it is not native to New England. It made its way to New England by being planted for utilitarian purposes, such as erosion control, and for its wood, which considered to be on of the most durable in North America. The wood can be used for items such as fence posts and ladder rungs.


HABITATS IN NEW ENGLAND

Abandoned Field,Edge,Open Disturbed Area,Pasture,Railroad Right-of-Way,Roadside,Utility Right-of-Way,Vacant Lot,Yard or Garden

Since Robinia pseudoacacia does not tolerate low light situations, it is usually found in disturbed areas where it can get full sun. It prefers sandy, well-drained soils, and does not grow well in poorly-drained situations.


THREATS

Robinia pseudoacacia rapidly spreads via root suckers and crowds out native vegetation. Damage to this plant only causes more root suckers and stump spouts to form. The seedlings also show this ability for rapid growth, however there is not a large amount of germination due to the inhibiting seed coat. It has been reported to grow up to 0.6 m (2 ft.) per year. Thus, it can form tall, dense, monotypic stands. It is also a great producer of nectar, which may allow it to compete with other species for pollinators. Finally, when growing in sandy areas this plant can enrich the soil by means of its nitrogen-fixing nodules, allowing other species to move in.


MANAGEMENT LINKS

Wisconsin Department of Natural Resources

The Connecticut Invasive Plant Working Group Invasive Plant Management Guide
Comprehensive management information.

Plant Conservation Alliance fact sheet
Includes management information


DOCUMENTATION NEEDS

Documentation required: Photograph of the habit or the flowers.
Best time for documentation: Spring, summer


ADDITIONAL INFORMATION

Integrated Taxonomic Information System
Has general taxonomic information about the species.

The PLANTS database
General information and a map

Virginia Tech Dendrology
Description and photographs

Ohio Perennial and Biennial Weed Guide
Photographs, general information, Facts and Folklore

Wisconsin Department of Natural Resources
General information and control


REFERENCES

Bailey, L. H.  1949.  Manual of Cultivated Plants.  Macmillan, New York.

Boring, L.R. and W.T. Swank. 1984. The role of black locust (Robinia pseudoacacia) in forest succession. Journal of Ecology 72: 749-766.

Britton, N.L. and A. Brown.  1972.  An Illustrated Flora of the United States and Canada vol. 2.  Dover Publications Inc., New York.

Dirr, M.A. 1983. Manual of Woody Landscape Plants. Stipes Publishing Company, Champaign, Illinois. 

Fernald, M.L.  1950.  Gray's Manual of Botany 8th edition.  American Book Company, New York.

Fire Conference 2000.  Proceedings of the Invasive Species Workshop: The Role of Fire in the Control and Spread of Invasive Species. The First National Congress on Fire Ecology, Prevention, and Management.  Tall Timbers Research Station, Miscellaneous Publication No. 11.

Gleason, H.A. and A.C. Cronquist.  1991.  Manual of Vascular Plants of the Northeastern United States and Adjacent Canada. 2nd ed.  New York Botanical Garden, Bronx, New York.

Hirschfeld, J.R., J.T. Finn and W.A. Patterson III 1984. Effects of Robinia pseudoacacia on leaf litter decomposition and nitrogen mineralization in a northern hardwood stand. Canadian Journal of Forestry Research 14: 201-205.

Holmgren, N.H. 1998. Illustrated Companion to Gleason and Cronquist's Manual.  New York Botanical Garden, Bronx, New York.

Magee, D.W and H.E. Ahles. 1999.  Flora of the Northeast. University of Massachusetts Press, Amherst.

USDA, NRCS.  2001.  The PLANTS Database, Version 3.1. (http://plants.usda.gov).  National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Yatazawa, M., G.G. Hambali and F. Uchino. 1983. Nitrogen fixing activity in warty lenticellate tree barks. Soil Science and Plant Nutrition 29: 285-294.