Black Locust

Robinia pseudoacacia

Copyright, Mark Brand, UConn Plant Database

John M. Randall, The Nature Conservancy

Black Locust is a medium-sized tree, growing up to 80 feet tall. It is easily recognized by its leaves and paired spines up to1/2 inch long.

Black Locusts prefer sandy or rocky soil, and are most often found in old fields, open areas, woods, and streamsides.

The leaves of this tree are pinnately compound, which means one leaf has many (7 - 19) leaflets on one main stem. Leaflets are always paired, except for the one on the end of the leaf. Leaf color is bluish-green on top, and pale underneath. The entire leaf is 6 to 12 inches long. Leaflets are oval-shaped and less than 2 inches long with no teeth and a bristle tip. At night leaflets fold up and droop.

James H. Miller, USDA Forest Service

James H. Miller, USDA Forest Service

Paul Wray, Iowa State University

Black Locust bark is light gray with deep furrows. The trunk is 1 to 2 feet wide.

Spines grow on twigs, close to where the leaves are attached. They are always in pairs.

Black Locust flowers are small, about 3/4 inch long, and pear-shaped. They each have five white petals, and many flowers grow together in a droopy cluster, 4 to 8 inches long. This tree blooms in late Spring.

If flowers get pollinated, fruits will grow. Locust fruits are pods, and Black Locust has dark brown pods up to 4 inches long. Pods stay attached to the tree in Winter, and each pod has up to 14 seeds in it.

Black Locust often grows alongside White Oak, Black Oak, Scarlet Oak, hickories, American Beech, Red Maple, Silver Maple, American Basswood, Yellow Poplar, Eastern Redcedar, American Elm, Black Cherry, White Ash, Black Walnut, Sassafras, Flowering Dogwood, Blackgum, and bluegrasses.

Black Locust flowers are pollinated by bees and hummingbirds. Seeds are eaten by Northern Bobwhite, Mourning Dove, Wild Turkey, White-tailed Deer, Eastern Cottontail, and squirrels. White-tailed Deer also eat leaves and twigs.

Many animals use this tree for cover, and cavities in Black Locust are good homes for bird and other animals, especially woodpeckers.

Bill Cook, Michigan State University

Copyright 2000, Joe DiTomaso

Paul Wray, Iowa State University

Black Locust is the host plant for Silver-spotted Skippers and Clouded Sulphur butterflies.

Black Locust does not compete well with other trees and does not tolerate shade, so it often gets crowded out. It grows very fast, but does not live long compared to most trees. It rarely lives to be 100 years old. Black Locust can survive drought and harsh winters.

This tree can send up new sprouts from roots and stumps, which may eventually turn into new trees.

Relationships in Nature:

Animals Using as Food Source
Animals Using as Shelter
Associations With Other Plants

White-tailed Deer

Downy Woodpecker

White Oak

Ruby-throated Hummingbird Po

Northern Bobwhite

Pileated Woodpecker

Mockernut Hickory

Golden Northern Bumble Bee Po

Eastern Gray Squirrel

Black Rat Snake

American Beech

Honey Bee Po

Honey Bee

Great Crested Flycatcher

Red Maple

Clouded Sulphur H

Golden Northern Bumble Bee


Eastern Redcedar

Silver-spotted Skipper H

Wild Turkey

Eastern Gray Squirrel

Yellow Poplar

Buffalo Treehopper Pa

Ruby-throated Hummingbird

Virginia Opossum

Silver Maple

Eastern Cottontail

Eastern Bluebird

Black Oak

Mourning Dove

Carolina Chickadee

American Elm

Silver-spotted Skipper

White-breasted Nuthatch

Black Cherry

Clouded Sulphur

Clouded Sulphur

White Ash

Buffalo Treehopper

Bald-faced Hornet


Buffalo Treehopper

Flowering Dogwood

Eastern White Pine

Kentucky Bluegrass

Bigtooth Aspen

Relationship to Humans:

Black Locust seeds are poisonous to humans. Wood is used for lumber, poles, fenceposts, paper, boxes, crates, pegs, stakes, and firewood. Black Locust is planted to stop soil erosion. It is also an important plant for bee-keeping. Locust trees are planted near hives so the bees can get nectar from the flowers and make honey.


Robinia pseudoacacia



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