Panicum amarum
Panicum trichoides
bitter beachgrass, bitter panicgrass, bitter panicum
small-flower panicgrass, tropical panicgrass
20-250 cm tall, 3-10 mm thick, erect or decumbent, simple or branched from the lower nodes;
nodes glabrous;
internodes glabrous, glaucous.
15-100 cm tall, 0.5-1(2) mm thick, sprawling to erect, without cormlike bases, freely branching and rooting from the lower nodes;
nodes prominent, glabrous or pubescent;
internodes not succulent, pilose.
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.
shorter than the internodes, rounded, hairs papillose-based;
collars pilose;
ligules 0.2-0.5 mm;
blades 2-7 cm long, 5-20 mm wide, 4-6 times longer than wide, lanceolate, thin, flat, sparsely to densely pilose, hairs papillose-based, bases asymmetrically cordate to subcordate, lower margins ciliate, papillose.
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.
4-24 cm, almost as wide as long, diffuse, partially included or exerted;
primary branches to 10 cm, alternate, ascending to reflexed, branching in the distal 2/3;
pedicels 9-20 mm, threadlike.
4-7.7 mm long, 1.5-2 mm wide, narrowly ovoid, glabrous, acuminate;
lower florets staminate.
1-1.4 mm long, 0.5-0.6 mm wide, not secund, lanceoloid to narrowly ovoid, plano-convex in side view, sparsely pubescent.
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.
glumes 0.4-0.8 mm, 1/3 – 1/2 as long as the spikelets, 1-3-veined, subacute;
upper glumes 0.8-1.2 mm, arising 0.2 mm above the lower glumes, 3-5-veined;
lower florets sterile;
lower lemmas 0.1-0.2 mm longer than the upper glumes, 3-5-veined;
lower paleas 0.5-0.8 mm, hyaline;
upper florets 0.8-1.2 mm long, 0.4-0.6 mm wide, finely rugose, lemmas strongly convex.
= 36, 54.
= 18.
Panicum amarum
Panicum trichoides
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 trichoides grows in moist, often weedy fields, woodlands, and savannahs of Mexico, Central and tropical America, and the Caribbean. It has been found, as a weed, in Brownsville and Austin, Texas, and is probably introduced to the Flora region. It has also been introduced into Africa, tropical Asia, and the Pacific islands. In the Flora region, it flowers from August through October.
(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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