Bristly Locust, Robinia hispida

Bristly locust

If you want a shrub or small tree that will turn heads when it’s in bloom and that’s very easy to grow why not try a Bristly Locust, (Robinia hispida)?  This lovely plant is unusual, pretty in bloom and not very utilized in American gardens, which is a shame.  It’s native to the southern Appalachian Mountains of the U.S. but is hardy to at least zone 4. 

Bristly Locust can be a spreader if it’s happy where it’s planted but that shouldn’t stop anyone from planting this useful native.  It will grow almost anywhere, on poor soil and on steep banks and the USDA recommends it as erosion control for steep slopes. It will grow on very acidic or polluted soils and has been used to reclaim old mining and industrial sites. Bristly locust also tolerates alkaline soil.   It will grow in wet or dry spots, sun or semi-shade.  It takes nitrogen from the air and brings it into the soil, making conditions better for other plants too.

Bristly Locust is a small tree or shrub. Its natural tendency is to sucker and produce thickets but in a garden setting it can be trained into a small tree 8-10 feet high or a multi-stemmed bush. It has compound leaves of up to 13 rounded leaflets.  It gets its name from the tiny, purple red hairs that rise from sticky glands all up and down the stems, on the flower buds and seed pods.  These hairs are not prickly, although they do serve to discourage animal browsing and insect feeding.  Older limbs may also develop a few thorns that are prickly.

It’s the flowers of the prickly locust that are its most endearing feature.  They are rosy pink and shaped like large sweet pea flowers.  They appear in drooping clusters at the end of branches and the trees are covered in bloom in late spring or early summer.  The blooms are very attractive both to humans and to bees, butterflies and hummingbirds.  They have a light scent.

The flowers turn into flat, brown pea like pods about 4 inches long with several flat, hard black seeds inside. These eventually split to release the seeds. If you collect seeds to start plants plant them as soon as possible for best results. 

The Bristly Locust makes an attractive screening hedge, or it can be trained into a small specimen tree as mentioned above by keeping suckers pruned and allowing only one stem.  If you don’t want the plant to spread plant it so that it can be regularly mowed around.  Prickly locust will spread and take up a lot of room if it gets a chance so beware of that if bringing it into a small yard.

Bristly locust has few diseases or pests to worry about, isn’t fussy at all about soil and seems to resist deer browsing.

Finding a Bristly Locust

One of the hardest parts of growing a Bristly locust would be finding one to buy.  Few nurseries carry the plants, you may want to look at nurseries that carry native plants.  Some soil conservation districts may still offer the plants.  If you can find someone who has a large stand of them and they give you permission to dig a sucker – (new plant coming from rhizomous roots) dig it in early spring, get as much of the long horizontal root as possible and re-plant it as soon as you get home.  Smaller plants transplant better.

If you find seeds for sale plant them as soon as you can after receiving them.  Soak the seed in warm water for several hours, and then use a nail clipper to clip a tiny hole in one end of the seed.  Plant the seed in pots of moist soil and put them in the refrigerator for 6 weeks or leave the pots outside over winter.  Better yet plant them out where you want them to grow in late summer or fall.  Mark the spot so you’ll know what’s coming up in the spring.

Other uses for Bristly Locust

The native range of the Bristly locust is the original homeland of the Cherokee people and they had several uses for the plant. They used the wood for making bows and building.  The roots were used to cure toothache.  When the Cherokee obtained cattle they fed Bristly Locust to them for good health.

Modern herbalists do not list remedies using Bristly Locust and some references consider the plant poisonous.

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