Bristly locust | The Morton Arboretum

Family (English) Pea
Family (botanic) Fabaceae
Tree or plant type Shrub
Foliage Deciduous (seasonally loses leaves)
Native locale North America
Size range Large shrub (more than 8 feet)
Light exposure Full sun (6 hrs direct light daily), Partial sun / shade (4-6 hrs light daily)
Hardiness zones Zone 5 (Northern Illinois), Zone 6 (City of Chicago), Zone 7, Zone 8
Soil preference Alkaline soil, Dry soil, Moist, Sandy soil, well-drained soil
Tolerances Alkaline soil, clay soil, Dry sites, Occasional drought, Road salt
Season of interest late spring, early summer, midsummer, late summer
Flower color and fragrance Purple
Shape or form Irregular, Multi-stemmed, Round, Thicket-forming, Upright
Growth rate Fast

Native geographic location and habitat:

Bristly locust is 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 Ruby-throated hummingbirds can be seen.

Bark color and texture:

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

Leaf or needle arrangement, size, shape, and texture:

Leaves are alternate and pinnately compound with 7 to 15 elliptical 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 axils 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 a flat pod, 2 to 3 inches long and very bristly. They are not very prolific.

Plant care:

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