Dichanthelium dichotomum
Plants in small or large clumps, with knotty crowns. Basal rosettes well-differentiated; blades ovate to lanceolate. Culms 20-100 cm, decumbent to erect, sometimes geniculate; nodes usually glabrous, sometimes sparsely pilose or densely bearded with retrorse hairs; internodes often purplish or olive green, lowest internodes usually glabrous, varying to sparsely pubescent; fall phase usually branching freely, especially from the nodes above the middle, ultimately forming dense, reclining fascicles of divergent branchlets with numerous reduced, thin, often involute blades, secondary panicles often reduced, with few spikelets. Cauline leaves 4-7; sheaths usually shorter than the internodes, usually glabrous, occasionally the lower sheaths sparsely to densely soft-pubescent, sheaths of the uppermost leaves sometimes with whitish glandular spots between the prominent veins, margins of all sheaths glabrous or ciliate; ligules absent or shorter than 1 mm, of hairs; blades 3.5-14 cm long, 5-14 mm wide, usually thin, distant, spreading to reflexed or (occasionally) ascending, yellow-green to purplish, usually glabrous on both surfaces or (at least the lower blades) more or less densely and softly pubescent, bases constricted (in narrow-bladed subspecies) or narrowly subcordate (in wide-bladed subspecies), margins glabrous or ciliate basally, glabrous distally, blades of the flag leaves usually spreading. Primary panicles 3-12 cm, long-exserted, usually with many spikelets; branches wiry, mostly spreading or ascending, usually glabrous, sometimes scabridulous. Spikelets 1.5-2.7 mm, usually ellipsoid or obovoid, green or purplish (at least at the base), glabrous or (less commonly) sparsely pubescent or puberulent, often prominently veined, obtuse to acute to beaked. Lower glumes usually less than 1/3 as long as the spikelets, obtuse to acute; upper glumes usually slightly shorter than or as long as the lower lemmas and upper florets (occasionally extending beyond the floret); lower florets sterile; upper florets 1.3-2 mm long, usually less than 1 mm wide, ellipsoid, subacute to obtuse.
Distribution
Conn., N.J., N.Y., Va., Del., D.C., Wis., W.Va., N.B., Ont., Mass., Maine, N.H., R.I., Vt., Fla., Tex., La., Tenn., N.C., S.C., Pa., Puerto Rico, Ark., Iowa, Md., Ala., Ill., Ga., Ind., Okla., Ohio, Mo., Minn., Mich., Miss., Ky.
Discussion
Dichanthelium dichotomum grows in dry, sandy, clayey, or rocky ground, often in woods, or (more commonly) in moist or wet places, including marshes, bogs, low woods, swamps, and the moist borders of lakes and ponds. Its range extends south from the Flora region into the Caribbean. It is a polymorphic and ubiquitous species, with many of its intergrading subspecies exhibiting traits of other widespread and variable species such as D. commutatum, D. laxiflorum, and D. sphaerocarpon, which often grow at the same sites.
Selected References
None.
Lower Taxa
Key
| 1 | Lower nodes hairy. | > 2 |
| 2 | Spikelets 1.5-1.8 mm long, upper floret 0.6-0.8 mm wide | Dichanthelium dichotomum subsp. microcarpon |
| 2 | Spikelets 1.8-2.5 mm long; upper floret 0.7-1.0 mm wide. | > 3 |
| 3 | Spikelets usually glabrous; midculm blades usually 5-7 mm wide | Dichanthelium dichotomum subsp. dichotomum |
| 3 | Spikelets pubescent; midculm blades usually 7-14 mm wide. | > 4 |
| 4 | Lower sheaths and blades glabrous or sparsely pubescent | Dichanthelium dichotomum subsp. nitidum |
| 4 | Lower sheaths and blades more or less densely velvety pubescent | Dichanthelium dichotomum subsp. mattamuskeetense |
| 1 | Lower nodes glabrous. | > 5 |
| 5 | Larger blades more than 1 cm wide; sheaths often with pale glandular spots between the prominent veins; spikelets 1.9-2.6 mm long, acute to beaked | Dichanthelium dichotomum subsp. yadkinense |
| 5 | Larger blades less than 1 cm wide; sheaths without glandular spots; spikelets 1.5-2.3 mm long, obtuse to subacute. | > 6 |
| 6 | Culms weak, ultimately reclining or sprawling, often flattened | Dichanthelium dichotomum subsp. lucidum |
| 6 | Culms erect, terete. | > 7 |
| 7 | Blades usually spreading; spikelets ellipsoid, 1.8-2.3 mm long, rarely purplish at the base | Dichanthelium dichotomum subsp. dichotomum |
| 7 | Blades usually ascending or erect; spikelets broadly ellipsoid or obovoid, 1.5-1.8 mm long, often purplish at the base | Dichanthelium dichotomum subsp. roanokense |