Summary ²

Robinia pseudoacacia, commonly known in its native territory as black locust, is a medium-sized deciduous tree native to the southeastern United States, but it has been widely planted and naturalized elsewhere in temperate North America, Europe, Southern Africa and Asia and is considered an invasive species in some areas.

Description ³

Family:
Fabaceae (Pea)

Height:
30 to 80 feet at maturity

Habit:
Single-stemmed tree; Crown shape irregular, typically rounded or upright; DBH typically 1½-3’, rarely growing up to 5’; Spreads rapidly via seed and root suckers; Fast-growing and short-lived

Leaves:
Leaves (4-16” long) are alternately attached and compound in groups of 7 to 23 leaflets. Leaflets (up to 2” long and ¾” across) are elliptic in shape, with smooth margins, rounded bases, and rounded tips that are occasionally notched.

Bark:
Young bark is green with white lenticels, turning red-brown with age. Young branches are covered in brown spines (up to ¾” long), which may persist or fall off with age. Mature bark is gray-brown with shallow furrows that become deep, forking ridges with age.

Flower:
Up to 30 white flowers hang in racemes (2-5” long) from branches. Individual flowers (up to 1” long and ¾” across) are irregular in shape, with 5 petals arranged in a pea-like structure. The upper petals form a banner with a greenish-yellow base, while the lower petals form a winged keel.

Fruit:
Fruit is a flat pod (up to 4” long), initially green in color, becoming reddish-brown at maturity. Pods contain up to 10 black and brown mottled seeds.

Bloom time:
June

Fall color:
Yellow to yellow-brown

Nicknames:
Common Locust, False Acacia, Pea Flower Locust, Green Locust, White Locust, Yellow Locust

Habitat:
Black locust prefers full sun, and moist to very well-drained soils with some loam content. It is commonly found in open woodlands, woodland edges, savannas, thickets, and roadsides, and is a commonly planted species in urban areas.

Wildlife Benefits:
Flowers are attractive to bees, butterflies, moths, and hummingbirds. Foliage is a food source for many species of caterpillars and other insects. Buds and seeds are a food source for rabbits and many species of birds. Provides nesting habitat and cover for birds and other wildlife.

Notes:
This species has a nitrogen-fixing root system.
Its bark, leaves, and seeds are highly poisonous if ingested.
This species is susceptible to storm damage, as well as insect damage from the locust borer (Megacyllene robiniae).
Black locust is an invasive species native to the Eastern United States.

References:
https://www.minnesotawildflowers.info/tree/black-locust
https://www.illinoiswildflowers.info/trees/plants/bl_locust.html
https://plants.ces.ncsu.edu/plants/robinia-pseudoacacia/
https://www.mortonarb.org/trees-plants/tree-plant-descriptions/black-locust-not-recommended

Range ³

Sources and Credits

1. (c) Ramsey-Washington Metro Watershed District, all rights reserved, uploaded by Ramsey-Washington Metro Watershed District
2. Adapted by Ramsey-Washington Metro Watershed District from a work by (c) Wikipedia, some rights reserved (CC BY-SA), https://en.wikipedia.org/wiki/Robinia_pseudoacacia
3. (c) Ramsey-Washington Metro Watershed District, some rights reserved (CC BY-SA)

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