Panicum amarum
Panicum diffusum
bitter beachgrass, bitter panicgrass, bitter panicum
spreading witchgrass, West Indian panicgrass
20-250 cm tall, 3-10 mm thick, erect or decumbent, simple or branched from the lower nodes;
nodes glabrous;
internodes glabrous, glaucous.
(6)25-100 cm, 0.5-3.5 mm thick, spreading to weakly ascending, usually freely branching;
nodes pilose, hairs spreading to ascending;
internodes pilose, with papillose-based hairs, or sparsely hispid.
shorter or longer than the internodes, not keeled, glabrous;
collars often glaucous and purplish;
ligules 1-5 mm;
blades 7-50 cm long, 2-13 mm wide, erect or ascending, firm, thick, flat basally, more or less involute towards the apices.
rounded, glabrous, margins shortly ciliate distally;
ligules 0.6-4 mm, of hairs;
blades (3)6-15 cm long, 1-5 mm wide, spreading, abaxial surfaces sparsely hirsute, adaxial surfaces more densely so, hairs papillose-based, midribs prominent and not white, margins involute, bases cuneate, apices subulate.
10-80 cm long, 2-17 cm wide, contracted, slightly nodding;
primary branches whorled or opposite, strongly ascending to appressed;
pedicels 0.5-15 mm, appressed to slightly divergent.
4-7.7 mm long, 1.5-2 mm wide, narrowly ovoid, glabrous, acuminate;
lower florets staminate.
2.1-2.9 mm long, 0.8-1 mm wide, glabrous.
and lower lemmas relatively thick;
lower glumes 2.8-4 mm, 1/2 - 4/5 as long as the spikelets, 3-9-veined, apices of the midveins sometimes scabridulous;
upper glumes and lower lemmas extending 1.5-3 mm beyond the upper florets, apices stiffly gaping;
upper glumes 3.9-7.6 mm, 5-9-veined;
lower lemmas slightly shorter than the upper glumes, 7-9-veined, lower paleas 3-7 mm, oblong-hastate, folded over the anthers;
lower florets staminate;
upper florets 2.4-3.9 mm long, 1-1.8 mm wide, narrowly ovoid to oblong, glabrous, smooth, shiny, lemma margins clasping the paleas only at the base.
panicles 3-35 cm long, about 1/2 as wide, shortly exserted;
axillary panicles smaller, not fully exserted;
rachises scabridulous;
primary branches usually solitary, sometimes paired, divergent and widely spaced, secondary branching mostly on the distal 1/3 of the primary branches;
pedicels 1-4 mm, spreading to appressed, confined to the distal portions of the secondary branches.
glumes 1-1.2 mm, to 1/2 as long as the spikelets, attenuate, 5-9-veined, veins anastomosing apically;
upper glumes and lower lemmas similar, extending about 0.5 mm beyond the upper florets, 11-13-veined;
lower florets sterile;
lower paleas 1-1.3 mm;
upper florets 1.5-1.8 mm long, 0.6-0.8 mm wide, smooth.
= 36, 54.
= 36.
Panicum amarum
Panicum diffusum
Panicum amarum grows in the coastal dunes, wet sandy soils, and the margins of swamps, along the Atlantic Ocean and the Gulf of Mexico from Connecticut to northeastern Mexico. It is also known, as an introduction, from a few inland locations in New Mexico, North Carolina, and West Virginia, as well as in the Bahamas and Cuba.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Panicum diffusum grows along river banks, ditches, and disturbed areas in wet, loamy or clayey soils. Its range extends from Texas to the Caribbean and northern South America.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Rhizomes short or ascending; culms often bunched and decumbent, usually more than 120 cm tall; lower glumes with 3-5 less evident veins, the midvein smooth distally; spikelet density high; panicles with 2 or more main branches per node; spikelets 4-5.9 mm long | subsp. amarulum |
1. Rhizomes horizontally elongate; culms mostly solitary, less than 150 cm tall; lower glumes with 7-9 prominent veins, the midvein scabridulous distally; spikelet density moderate; panicles with 1 or 2 main branches per node; spikelets 4.7-7.7 mm long | subsp. amarum |
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