Please try our next iteration of the Michigan Flora Online here. Beginning on February 1, 2023, will point to this new site.

The new site offers several benefits over the existing website, including real coordinate mapping, giving a clearer view of the density of documentation as well as more precision about plant distributions and their link to landforms. We will also have the ability to update species pages more regularly, both in terms of new collections and as more existing Michigan specimens are georeferenced. In addition, we have a better photo display, and offer indented keys.


1. Leaves entire to deeply lobed, or (3 species) if coarsely serrate, then finely stellate-pubescent over the lower surface; nut an “acorn,” terete, seated (solitary) in a shallow to deep scaly cup which remains intact.


1. Leaves sharply and regularly serrate, glabrous to silky-pubescent (not stellate) along the veins beneath; nut slightly to strongly flattened on at least one side, enclosed (usually 2–3 together) in a prickly involucre (husk or bur), which splits into (2–) 4 valves.

2. Teeth of leaves mostly 2–5 mm long, acuminate and often somewhat incurved; flowers in midsummer, after leaves are fully developed, the staminate ones in elongate, stiff, essentially sessile aments; fruiting involucre over 2 cm long, densely covered with stiff and sharp branched spines and normally containing 2–3 somewhat flattened but not sharply angled nuts; winter buds less than 1 cm long; bark ridged and furrowed, brownish.


2. Teeth of leaves at most 1.5 (–2) mm long (measured along upper margin); flowers appearing in spring, at same time as the leaves, the staminate ones in a peduncled, pendent, spherical ament; fruiting involucre ca. 2 cm long or less, bearing weak unbranched spines and normally containing 2 sharply 3-angled nuts; winter buds over 1 cm long; bark smooth and gray.



MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. January 29, 2023.