The most striking aspect of this shrub consists of the bristly purple-brown hairs that cover young stems, pedicels, calyces, and seedpods. These hairs probably discourage herbivory by some insects and deter nectar-robbing of the flowers by ants. Another species in this genus with a similar appearance is Robinia viscosa (Clammy Locust). While stems, calyces, seedpods, etc. of this shrub are covered by short sticky glands, they lack the long purple-brown hairs of Bristly Locust. Another species, Robinia pseudoacacia (Black Locust), is a tree that has spread northward into all areas of Illinois. This tree also lacks the long purple-brown hairs of Bristly Locust and its flowers are white, rather than rosy pink. In its native range in southeastern United States, Bristly Locust is a rather variable shrub and different varieties have been described. The typical variety (var. hispida) has been described here because it is more often encountered than other varieties of this shrub.