1 Corolla 8-11 mm long; petioles mostly 1-8 mm long; [DE, MD, VA, KY, MO, OK northwards]

1 Corolla 3-8 (-9) mm long (or 8-10 mm long in D. laevigatum); petioles mostly longer, mostly 10-60 mm long (except D. ciliare and D. obtusum); [collectively widespread in our area].

  2 Loment with 1-3 segments, rounded below.

    3 Leaflets cinereous on the lower surface; corolla 6-7 mm long; loment with 3 (-4) segments

    3 Leaflets not cinereous on the lower surface; corolla 3.5-6 mm long; loment with 1-2 (-3) segments; [“Desmodium ciliare group”].

      4 Leaflets 3-5.5× as long as wide

      4 Leaflets 1.2-3.5× as long as wide.

        5 Terminal leaflet similar to the lateral leaflets; stem (near the middle) glabrous to pilose, or also with some uncinate-pubescence.

          6 Petioles 1-3 (-5) mm long; pedicels 3-8 mm long; stem usually pilose; leaflets sub-appressed pubescent (to glabrate)

          6 Petioles 10-25 mm long; pedicels 8-15 mm long; stem glabrous (to sparsely uncinate-puberulent); leaflets glabrous or with only a few scattered hairs

  2 Loment with 2-5 segments, mostly obtusely angled below.

             7 Leaves densely villous on the lower surface; stem densely pubescent with uncinate or non-uncinate hairs.

               8 Leaflets 1.5-2.0 (-2.2)× as long as wide; loment usually curved (the upper margin convex); loment with 2-4 segments; loment segments 4-7 mm long

               8 Leaflets 1.0-1.5 (-1.9)× as long as wide; loment straight; loment with (3-) 4-5 (-6) segments; loment segments 5-8 (-9) mm long

             7 Leaves glabrous to moderately appressed-villous on the lower surface; stem glabrate, pilose or uncinate pubescent.

                 9 Bracts (subtending clusters of 2-3 flowers) usually villous; plants moderately to densely villous; loment usually incurved (the upper margin convex); loment with 2-4 segments, each segment 4-5 mm long

                 9 Bracts (subtending clusters of 2-3 flowers) not villous; plants glabrous or slightly to moderately villous or pilose; loment usually nearly straight; loment with 3-5 segments, each segment 4-8.5 mm long.

                   10 Corolla 8-10 mm long; pedicels usually 10-15 (-20) mm long; stems and leaves glabrous; leaflets distinctly pale on the lower surface

                   10 Corolla 6-8 (-9) mm long; pedicels 3-12 mm long; stems and leaves pubescent or glabrate (but pubescent at least on the leaves); leaflets green or slightly pale on the lower surface; [“Desmodium paniculatum group”].

                     11 Leaflet lower surface glabrous, except for the conspicuous uncinate puberulence on the veins; stems and petioles glabrous or uncinate-puberulent; [plant of the Coastal Plain and possibly lower Piedmont]

                     11 Leaflet lower surface strigose to conspicuously sub-appressed-villous, and sometimes also uncinate-puberulent; stems and petioles glabrate to conspicuously pilose or uncinate-puberulent; [plants collectively widespread in our area].

                       12 Leaflets (2.5-) 3-8 (-10)× as long as wide; leaflet pubescence usually sparse, of straight, appressed hairs < 0.5 mm long (or sometimes of longer spreading hairs); leaflets usually lacking uncinate pubescence on either surface; mid-stems glabrous or glabrate, the pubescence usually uncinate puberulence.

                          13 Loment segments rounded on the lower margin (thus semicircular to gibbous); leaves subsessile to short-petiolate; [plant restricted to Coastal Plain]

                          13 Loment segments angled on the lower margin (thus triangular to sub-rhombic); leaves long-petiolate; [plant widespread in our area]

                       12 Leaflets 1.5-3 (-4)× as long as wide; leaflet pubescence usually evident, of spreading hairs > 0.5 mm long; leaflets usually with uncinate pubescence on the veins of the upper surface; mid-stems pubescent, either pilose or with uncinate pubescence (if not, evidently pubescent on the petioles).

                            14 Each side (from the isthmus on one side of the article to the broadest point) of the ventral margin of most articles straight to slightly convex; leaves gradually but noticeably reduced in size and petiole length distally along the stem, often with small leaves extending well onto the flowering branches; terminal leaflets lanceolate to broadly ovate (most specimens, especially of full sun habitats, are on the narrow end of this range), broadest nearer the base than the middle

                            14 Each side (from the isthmus on one side of the article to the broadest point) of the ventral margin of most articles concave; leaves mostly all the same size and not or little extending onto the flowering branches (the few leaves that do extend into the inflorescence branches will also be reduced in size but more abruptly so); terminal leaflets narrowly ovate to broadly elliptic-ovate (most specimens are on the wider end of this range), broadest nearer the middle than the base