1. Underside of fully expanded leaf blades densely and evenly covered with a persistently adherent rust-colored tomentum concealing the entire surface between the veins; stems regularly with tendrils (or peduncles) at 3 or more consecutive nodes; ripe fruit at least 15 mm in diameter.
1. Underside of fully expanded leaf blades glabrous or with thin or very uneven (tufted) pubescence exposing much of the surface between the veins; stems with tendrils (or peduncles) at no more than 2 consecutive nodes; ripe fruit less than 10 (–15) mm in diameter.
2. Mature leaf blades distinctly whitened or glaucous beneath, with scattered or tufted pale to rust-colored cobwebby hairs at least along the principal veins; leaf margins with shallow, obtuse teeth usually not ciliate, the sinuses between lobes (if any) broadly angled or rounded.
2. Mature leaf blades green or yellowish green beneath, not glaucous, with sparse or no cobwebby hairs; leaf margins with teeth various but acute and minutely ciliate in common species, without lobes or (usually) with acute sinuses between lobes.
3. Lobes of leaf well developed, at least on later leaves of the season, pointed forwards; margins with acute teeth, also ± pointed forwards, ciliate; ripe fruit glaucous; common throughout Michigan.
3. Lobes of leaf none or weakly developed and pointing outwards; margins with obtuse teeth (except for a small apiculus), usually not or sparsely ciliate, except early in the season; ripe fruit purple-black, not glaucous; rare, in southernmost Michigan.
All species found in Vitis
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 18, 2017. http://www.michiganflora.net/genus.aspx?id=Vitis.