1 Tendrils simple; bark adherent (on all but the largest stems), with prominent lenticels; pith continuous through nodes; leaves relatively small (< 10 cm long and wide) and coarsely toothed, pentagonal in outline but never deeply lobed

1 Tendrils bifid to trifid; bark shedding, the lenticels inconspicuous; pith interrupted by diaphragms at nodes; leaves relatively large (well-developed leaves usually > 10 cm wide and long) and finely toothed, often deeply lobed.

  2 Flowers bisexual; berries ellipsoid, longer than broad; berry with pulp adhering to skin; [exotic and cultivated, rarely persistent]

  2 Flowers functionally unisexual; berries globose (isodiametric); berry with skin separating from pulp; [native, collectively widespread].

    3 Mature leaves glaucous beneath (the glaucescence sometimes rather obscured by pubescence); nodes often glaucous; inflorescence rachis (flowering and young-fruiting) orange-red arachnoid-pubescent; [series Aestivales].

      4 Mature 3-4-seeded berries < 9 mm in diameter; mature leaves glabrous to glabrate beneath; nodes usually glaucous; nodal diaphragms usually < 2 mm in diameter

      4 Mature 3-4-seeded berries > 9 mm in diameter; mature leaves slightly to strongly arachnoid-pubescent beneath; nodes usually not glaucous; nodal diaphragms usually > 2 mm in diameter

        5 Twigs and petioles nearly or completely glabrous

        5 Twigs and petioles rusty-tomentose.

          6 Mature 3-4-seeded berries > 14 mm in diameter; [west of the Mississippi River]

          6 Mature 3-4-seeded berries 9-14 mm in diameter; [east of the Mississippi River]

    3 Mature leaves not glaucous beneath; nodes not glaucous; inflorescence rachis (flowering and young-fruiting) glabrous, hispid, or white-floccose.

             7 Leaves densely pubescent beneath, so as to obscure the surface; [series Labruscae or hybrid involving that series].

               8 Tendrils or inflorescences present at 3 or more consecutive nodes.

                 9 Lower leaf surface densely arachnoid-tomentose when young, sparsely so at maturity, the surface visible through the hairs, or the hairs only on the veins; tendrils usually not at all nodes

                 9 Lower leaf surface densely and persistently arachnoid-tomentose, the surface (except major veins) hidden by the hairs; tendrils at almost all nodes.

                   10 Fruits many, 25-50 in well-developed clusters, the clusters ovoid and well branched, distinctly longer than broad; leaves densely arachnoid-tomentose at maturity

                   10 Fruits few, < 20, in a simple globose or spheroidal cluster, about as wide as long; leaves moderately arachnoid-tomentose at maturity

               8 Tendrils or inflorescences present at only 2 consecutive nodes.

                     11 Stipules 1.5-4 mm long; nodal diaphragms 1.5-3 mm thick; [AL, MS, LA, TX, and OK]

                     11 Stipules < 1 mm long; nodal diaphragms 2.5-6 mm thick; [FL and s. AL]

             7 Leaves glabrous or somewhat pubescent beneath (but not so densely as to completely obscure the leaf surface).

                       12 Leaves reniform (wider than long when flattened), folded along the midvein (V-shaped); leaf lower surface glabrous at maturity; tendrils either absent, or when present, only opposite the uppermost nodes (or sometimes extending down the stem); inflorescence rachis (flowering or early-fruiting) glabrous or glabrescent; [series Ripariae]

                       12 Leaves cordate to cordate-ovate (about as wide as long, or longer than wide), not prominently folded along the midvein (near planar); leaf surface glabrous to pubescent at maturity; tendrils present opposite most nodes; inflorescence rachis (flowering or early-fruiting) glabrous, glabrescent, hispid, or white-floccose.

                          13 Nodal diaphragms < 1 mm wide, usually < 0.5 mm wide; growing shoot tips enveloped by enlarging, unfolded leaves; inflorescence rachis (flowering or early-fruiting) glabrous or glabrescent; [section Ripariae]

                          13 Nodal diaphragms > 1 mm wide; growing shoot tips not enveloped by enlarging, unfolded leaves; inflorescence axis (flowering or early-fruiting) hispid and/or white-floccose.

                            14 Branchlets of the season more or less terete, glabrous or arachnoid-pubescent; mature 3-4 seeded berries usually > 8 mm in diameter; nodes usually not banded with red pigmentation; inflorescence rachis (flowering or early-fruiting) densely hispid (never floccose); [series Cordifoliae].

                              15 Nodal diaphragms > 2.5 mm wide; leaves strongly 3-lobed, the tips usually long-acuminate; branchlets of the season with a red or purplish cast

                              15 Nodal diaphragms < 2.5 mm wide; leaves unlobed or shallowly lobed, the tips acute to short-acuminate; branchlets of the season gray, green, or brown (sometimes purple only on one side)

                            14 Branchlets of the season angled, arachnoid-pubescent and/or hirtellous-pubescent (or nearly glabrous); mature 3-4 seeded berries < 8 mm in diameter; nodes frequently banded with red pigmentation; inflorescence rachis (flowering or early-fruiting) white-floccose (and sometimes also hispid); [series Cinerescentes].

                                16 Branchlets of the season sparsely to densely hirtellous pubescent, often with arachnoid pubescence as well; leaf undersurfaces usually more-or-less uniformly hirtellous on the veins; [western, east to w. KY, w. TN, sc. AL, and Panhandle FL]

                                16 Branchlets of the season lacking evident hirtellous trichomes (if present, obscured by the arachnoid pubescence; leaf undersurfaces lacking hirtellous pubescence, or only very sparsely so; [collectively widespread in our area].

                                  17 Branchlets glabrate to only slightly arachnoid-pubescent; nodes usually banded with red pigmentation; leaves glabrous to very slightly arachnoid-pubescent beneath; [mostly of the Piedmont and Mountains]