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.
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.
Culms occasionally more than 60 cm, very slender, weak; nodes usually
glabrous; internodes often flattened, green, glabrous; fall phase
with reclining or decumbent culms and numerous axillary branches, branches elongated
and widely divergent, not forming fascicles. Cauline sheaths usually shorter
than the internodes, glabrous; blades slightly smaller than those of
the other subspecies, ascending or spreading, often lustrous, bright green,
glabrous throughout. Primary panicles slightly smaller and with fewer
spikelets than in the other subspecies (particularly subsp. dichotomum,
which it closely resembles). Spikelets 1.8-2.3 mm, ellipsoid, usually
glabrous, obtuse to subacute; upper florets 1.7-2 mm. 2n = unknown.
Dichanthelium dichotomum subsp. lucidum grows in wet woods, the
margins of cypress swamps, sphagnum bogs, and other similar, wet habitats. It
is primarily a species of the coastal plain, ranging from New Jersey to Florida,
southeastern Texas, and up the Mississippi embayment to western Tennessee and,
as a disjunct, on the Indiana Dunes of Lake Michigan.
Culms 30-100 cm, slender, erect or geniculate; fall phase freely
branching from all nodes, reclining from masses of branchlets and numerous reduced,
ciliate blades and secondary panicles; nodes conspicuously bearded with
retrorse hairs. Sheaths usually glabrous, lowermost sheaths sometimes
sparsely pubescent, occasionally with whitish spots between the veins, ciliate
along the margins; blades 5-14 cm long, 5-14 mm wide, thin, spreading
to reflexed, glabrous on both surfaces, bases with few to many papillose-based
cilia. Panicles 5-12 cm, well-exserted, dense. Spikelets 1.5-1.8
mm, usually glabrous, rarely slightly pubescent. Lower glumes usually
less than 1/4 as long as the spikelets; upper glumes usually shorter
than the lower lemmas; upper florets 1.3-1.6 mm long, 0.6-0.8 mm wide,
subacute. 2n = 18.
Dichanthelium dichotomum subsp. microcarpon grows in wet woods,
swamps, and wetland borders. It is a widespread subspecies, extending from southern
Michigan to Massachusetts and south to eastern Oklahoma and Texas and throughout
the southeast to central Florida.
Plants very similar in most respects to subsp. microcarpon. Fall
phase freely branching from all nodes, reclining from masses of branchlets
and numerous reduced, ciliate blades and secondary panicles. Cauline sheaths
and blades usually glabrous, lower sheaths and blades sometimes sparsely
pubescent. Spikelets 1.8-2.5 mm (rarely longer), puberulent or pubescent.
Lower glumes less than 1/3 as long as the spikelets, subacute; upper
glumes and lower lemmas subequal; upper florets 1.7-2 mm long,
0.7-1.0 mm wide, subobtuse. 2n = unknown.
Dichanthelium dichotomum subsp. nitidum grows in moist to wet areas,
and the borders of swamps. It is primarily a coastal plain taxon, ranging from
Virginia to southeastern Texas and Florida.
Dichanthelium dichotomum subsp. nitidum is very
similar to both subsp. microcarpon and subsp. mattamuskeetense, and intergrades with each occasionally.
Culms to 100 cm, erect; nodes usually glabrous; internode s terete,
usually glabrous, often slightly glaucous, sometimes olivaceous; fall phase
with erect or decumbent culms, branching at the mid- and upper culm nodes, with
numerous axillary branches, branches elongated and widely divergent, not forming
fascicles. Cauline sheaths glabrous or the lowest sheaths sparsely pubescent;
blades usually 5-8 mm wide, stiffly ascending or erect, often olivaceous
or purplish abaxially, glabrous or sparsely pubescent basally. Spikelets
1.5-1.8 mm (seldom longer), broadly ellipsoid or obovoid, often purplish at
the base, glabrous, obtuse to subacute. Upper florets 1.4-1.6 mm, broadly
ellipsoid. 2n = unknown.
Dichanthelium dichotomum subsp. roanokense grows in marshes, wet
pinelands, wet woods, and the borders of swamps. A relatively uncommon subspecies,
it grows on the coastal plain from Delaware to southeastern Texas and in the
West Indies. It is very similar to subsp. dichotomum and also exhibits traits of D. sphaerocarpon and D. erectifolium.
Culms few, erect, or geniculate at base, 6-10 dm, glabrous; sheaths glabrous or sparsely ciliate, especially distally, those of the primary stems usually with pale, glandular spots on the back; blades thin, bright green, 6-12 mm wide, glabrous, or sparsely ciliate at base; primary panicle 6-10 cm, about as wide, its lower branches ascending; spikelets ellipsoid, pointed, glabrous, 2-2.5 mm; first glume subacute, two-fifths as long; second glume and sterile lemma distinctly surpassing the fr; autumnal phase erect or nearly so, sparsely and loosely branched from the middle nodes, the branches 1-2 dm, the blades 2-5 cm נ2-5 mm, the panicles much reduced, about equaling the uppermost lvs; 2n=18. Moist or wet woods; N.J. to s. Ill., s. to Ga. and La. Vegetatively resembling luxuriant plants of no. 30 [Panicum dichotomum L.].
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.