Bristly locust

Flowers and leaves of bristly locust.

Bristly locust is an upright, suckering shrub used to stabilize slopes. The purplish-pink pendulous flowers, blue-green foliage, bristle seed pods add seasonal interest. May be difficult to find in nurseries.

Botanical name:

Robinia hispida

All Common Names:

bristly locust; rose acacia; roseacacia locust

Family (English):

Pea

Family (Botanic):

Fabaceae

Tree or Plant Type:

  • Shrub

Foliage:

  • Deciduous (seasonally loses leaves)

Native Locale:

  • Non-native

Landscape Uses:

  • Hedge,
  • Massing,
  • Screen,
  • Windbreak

Size Range:

  • Large shrub (more than 8 feet)

Mature Height:

6 to 10 feet high

Mature Width:

10 to 15 feet wide

Light Exposure:

  • Full sun (6 hrs direct light daily),
  • Partial sun/shade (4-6 hrs light daily)

Hardiness Zones:

  • Zone 5 (Chicago),
  • Zone 6,
  • Zone 7,
  • Zone 8

Soil Preference:

  • Alkaline soil,
  • Dry soil,
  • Moist, well-drained soil,
  • Sandy soil

Acid Soils:

  • Tolerant

Alkaline Soils:

  • Tolerant

Salt Spray:

  • Tolerant

Soil Salt:

  • Tolerant

Drought Conditions:

  • Tolerant

Poor Drainage:

  • Intolerant

Planting Considerations:

  • Dangerous thorns,
  • Excessive sucker growth,
  • May be difficult to find in nurseries

Ornamental Interest:

  • Spring blossoms,
  • Persistent fruit/seeds,
  • Showy flowers,
  • Attractive bark

Season of Interest:

  • Late spring,
  • Early summer,
  • Mid summer,
  • Late summer

Flower Color & Fragrance:

  • Purple

Shape or Form:

  • Irregular,
  • Multi-stemmed,
  • Round,
  • Thicket-forming,
  • Upright

Growth Rate:

  • Fast

More Information:

Tree & Plant Care

A large, suckering shrub up to  8 feet high with a spreading fan-shaped crown. Spreads by suckers creating thickets.
Best planted in full to part sun in all soils, including those that contain clay or sand. 
Prune regularly to keep in bounds.
Bristly locust has appeared on some invasive lists.

Disease, pests, and problems

Stem canker, mildew, leaf spots, leaf miner, scale, and borer

Disease, pest, and problem resistance

Tolerant of salt spray

Native geographic location and habitat

Native to North America

Attracts birds, pollinators, or wildlife

The nectar of the flowers attracts honeybees, bumblebees, and other long-tongued bees; occasional butterflies (which are poor pollinators), and possibly the Ruby-throated Hummingbird.

Bark color and texture 

The bark of the trunk and larger branches is gray and fairly smooth. Young branches are zigzag, green with very bristly-hairs. These long bristly hairs are purple-brown and sticky.

Leaf or needle arrangement, size, shape, and texture

Alternate, pinnately compound with elliptical 7 to 15 leaflets. The green stalk (rachis) is sticky, hairy and has a pair of sharp spines at the base. Upper leaves are medium green while their lower surfaces are pale green.

Flower arrangement, shape, and size

Attractive, rose-colored, pea-like flowers in hanging clusters are located in leaf axis and at the end of branches. Bloom period is late spring to mid-summer.

Fruit, cone, nut, and seed descriptions

Fertile flowers are replaced by flat pod, 2 to 3 inches long and very bristly.  Not very prolific.

Location of Robinia hispida (Bristly locust) at the Arboretum