The flowers of all our species have a yellow spot at the base of the standard, whatever the color of the rest of the corolla. All are shrubs or small to medium-sized trees in Michigan, escaped from cultivation or spread by the vigorous suckering habit. Other species and hybrids of Robinia are cultivated and may spread, at least by root suckers. 

1. Corolla white; branchlets smooth, the year-old ones glabrous.

R. pseudoacacia

1. Corolla pink to rose-purple; branchlets hispid or glandular-viscid.

2. Branchlets hispid with stiff spreading hairs (at most with tiny gland-tips).

R. hispida

2. Branchlets viscid with conspicuous sessile or subsessile warty glands, but not hispid.

R. viscosa