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 trees in Michigan, escaped from cultivation or spread by the vigorous suckering habit.
Shrubs resembling a Robinia but with yellow flowers and inflated fruit (over a third as broad as long) are likely to be Colutea arborescens L., bladder-senna, a native of Europe and northern Africa which has been collected in Muskegon Co., but without notation of whether escaped or planted.
1. Corolla white; branchlets smooth, the year-old ones glabrous.
1. Corolla pink to rose-purple; branchlets hispid or glandular-viscid.
2. Branchlets hispid with stiff spreading hairs (at most with tiny gland-tips).
2. Branchlets viscid with conspicuous sessile or subsessile warty glands, but not hispid.
All species found in Robinia
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. August 16, 2017. http://michiganflora.net/genus.aspx?id=Robinia.