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Dichanthelium
See list of 16 species in this genusSee references under Panicum for evidence for segregation of this genus. Many species of Dichanthelium flower twice during the growing season. In early to mid-summer, the chasmogamous primary panicle is produced at the summit of the main stem. Later, lateral branches and secondary panicles are produced, the secondary panicles are often partially or completely enclosed in leaf sheaths and are cleistogamous. Care needs to be taken when identifying species of Dichanthelium because the character states are sometimes different between the main stems and chasmogamous panicles and the lateral branches and cleistogamous panicles, the latter appearing in the later season. The following key is written for the main stems and chasmogamous panicles. Reference: Freckmann and Lelong (2003a).
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1a. Basal and lower stem leaf blades similar in shape, elongate and narrow, (6.3–) 9.6–30 times as long as wide, erect to ascending, crowded [Fig. 213]; reproductive stems with 2–4 leaves
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2a. Upper glume and lower lemma pointed at the apex and surpassing the upper (i.e., fertile) lemma by (0.2–) 0.5–1 mm; spikelets 3.2–4.3 mm long; terminal panicle with 7–20 (–25) spikelets
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2b. Upper glume and lower lemma rounded to subacute at the apex, not surpassing upper lemma or surpassing it by no more than 0.3 mm; spikelets 2–3.2 mm long; terminal panicle with (12–) 20–70 spikelets
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1b. Basal and lower stem leaf blades dissimilar, the crowded basal leaves ovate to lanceolate and spreading, 2.3–7.3 times as long as wide, the stem leaf blades longer and only rarely crowded; reproductive stems with 3–14 leaves
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3a. Leaf blades with a white or green-white cartilaginous margin, cordate at base; spikelets 1.4–1.8 mm long, obovoid-spherical, nearly as wide as long
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3b. Leaf blades without or with a poorly developed cartilaginous margin, cordate to narrowed at base; spikelets 0.8–5.2 mm long, ellipsoid to obovoid, distinctly longer than wide
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4a. Leaf sheaths viscid near the apex, especially on the surface away from the margins, long spreading-pubescent with ± soft hairs except near the base where moderately to densely retorse-pubescent above a prominent, glabrous, viscid band [Fig. 214]
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4b. Leaf sheaths not viscid near the apex, variously glabrous or pubescent, without or, less commonly, with a prominent band of retrorse pubescence at the base, lacking a viscid band at the base
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5a. Ligules composed of a membranous base that is ciliate apically; plants from rhizomes (usually from caudices in D. commutatum); leaf blades 5–40 mm wide, truncate to cordate at base (often narrowed to the base in D. xanthophysum)
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6a. Leaf blades strictly ascending to erect; panicle usually cylindrical, 1–4 (–5) cm wide, more than 2 times as tall as wide, with strictly ascending to erect branches [Fig. 215]; spikelets rounded at apex
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6b. Leaf blades spreading to ascending; panicle usually broader, (3–) 4–13 cm wide, mostly 1–2 times as long as wide, with spreading to ascending branches; spikelets pointed to bluntly pointed at apex
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7a. Leaf sheaths pubescent with pustulose-based hairs [Fig. 212]; rhizomes 3–5 mm thick; reproductive stems with (5–) 7–14 leaves
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8a. Upper glume and lower lemma obtuse to subacute (note: those of the secondary panicles often sharply acute at the apex), not or hardly surpassing the upper lemma; leaf blades 15–30 mm wide, flat to the tip; spikelets sparsely pubescent
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8b. Upper glume and lower lemma acute to long-acute, surpassing the upper lemma; leaf blades 7–15 mm wide, tapering to an involute tip; spikelets glabrous or sparsely pubescent
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7b. Leaf sheaths glabrous or pubescent with non-pustulose-based hairs; rhizomes up to 2 mm thick or absent; reproductive stems with 4–6 leaves
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9a. Stems densely crisp-puberulent; ligules up to 0.3 mm long; spikelets 2.2–3.2 mm long; stem leaf blades 5–10 mm wide; plants from caudices
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9b. Stems glabrous or shortly pilose; ligules 0.4–0.9 mm long; spikelets 2.9–5.2 mm long; stem leaf blades 15–40 mm wide; plants from knotty rhizomes
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10a. Spikelets 2.9–3.9 mm long; nodes nearly glabrous to sparsely (rarely moderately) pubescent with retrorsely oriented hairs, the longer hairs up to 0.8 (–1.4) mm long
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10b. Spikelets 3.8–5.2 mm long; nodes moderately to densely (rarely sparsely) pubescent with retrorsely oriented hairs, the longer hairs 1.3–3.4 mm long [Fig. 211]
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5b. Ligules composed entirely of hairs; plants from caudices; leaf blades 2–12 (–15) mm wide, narrowed to rounded at the base (truncate to cordate in D. boreale and some D. dichotomum)
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11a. Spikelets 2.7–4.2 mm long; upper glumes often with a purple or orange-tan to orange spot or blotch near the base, strongly veined
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11b. Spikelets 0.8–2.6 mm long; upper glumes usually without an orange or purple area at base, weakly to strongly veined
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12a. Ligule a conspicuous band of hairs 1–5 mm tall that protrudes above the summit of the sheath
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13a. Spikelets 0.8–1 (–1.1) mm long; stems 0.3–0.8 mm thick
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13b. Spikelets 1.3–2.6 mm long; stems thicker than (0.8–) 1 mm
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14a. Spikelets 1.3–2.1 mm long; sheaths glabrous or with hairs usually shorter than 2 (–3) mm
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14b. Spikelets 2.1–2.6 mm long; sheaths pubescent with hairs 2–4 mm long
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12b. Ligule nearly absent or up to 1 mm long, the hairs hardly protruding above the summit of the sheath
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15a. Spikelets pubescent; nodes of stem glabrous; leaf blades truncate to cordate at base; uppermost stem leaf erect or ascending; spikelets (1.9–) 2–2.2 (–2.3) mm long
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15b. Spikelets glabrous or pubescent; nodes of stem glabrous or the lower nodes slightly to evidently retrorse-pubescent; leaf blades narrowed to the base in common forms (varying to truncate to cordate); uppermost stem leaf usually spreading; spikelets 1.5–2.5 mm long
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Each photo represents one species in this genus.