Bristly locust
Robinia hispidaFabaceae
Whole Plant
Whole PlantFlowerLeafStem
Photos (c) Cheryl Comeau Beaton unless otherwise noted

The Plant:

  • A deciduous shrub, around 8 feet tall.

The Leaves:

  • alternate
  • pinnately compound
  • 7 to 13 egg-shaped leaflets
  • stems hairy
  • thorns around some buds

The Stem:

  • young twigs covered with stout, bristly hairs

The Flowers:

  • Pink and pea-like, five-petaled flowers fragrant and growing in hanging clusters. Blooms from June through July.

The Fruits:

  • often does not produce fruit
  • long flat pod, very bristly
  • October
  • persists
  • dried brown

The Habitat:

  • full sun
  • tolerant of dry, sandy conditions
  • fixes nitrogen


  • mechanically dispersed seeds
  • spreads vegetatively by root suckers

Key ID Features:

  • stout, bristly hairs on young and green stems

Similar Species:

  • Honey locust (Gleditsia triacanthos) has pinnate leaves or it may have bipinnate leaves. It also has much larger spines, smaller, yellow-green flowers and long twisted pods, while Bristly locust has straight pods.
  • Two other locusts that also have invasive tendencies are Black locust (R. pseudoacacia), which has smooth stems, elliptic leaflets, and white flowers, and Clammy locust (R. viscosa), which has sticky, gland-covered stems and paler pink flowers.


  • On Nantucket, this species can be found in the wild in Quaise, Squam and Quidnet, though it is not clear what the source of the populations was.

Growth Form: Shrub

Origin: Southeastern United States, North Central United States, Lower Northeastern United States

Level of Invasiveness for Nantucket: Do not list at this time

Level of Invasiveness for Massachusetts: Not evaluated

Massachusetts Cultivation Restrictions: no

Credits: The Electronic Field Guide to the Invasive Plants of Nantucket (c) 2005-2006 Maria Mitchell Association, EFG Project, UMass Boston