Panicum subalbidum Kunth

Panicum subalbidum is a large vivacious grass (or annual), that develops in loose clumps, shortly rhizomatous. It first grows by spreading on the ground, then move upright to reach 1 to 2 m high. The stems are geniculate, glabrous, quite often soft and spongy, with blackish nodes. The leaves have a linear lamina, flat, smooth, very variable in size (7 to 40 cm long), with a short membranous ligule, ciliated at the apex. The inflorescence is branched, 15 to 40 cm long, often contracted, with close and erect or more ample branches and  with spreading branches. The spikelets are lanceolate, slightly compressed, 2.5 to 3 mm long, smooth, greenish yellow or stained with purple.
 
First leaves

The first leaves are simple, alternate, with rolled prefoliation, glabrous and more or less colored. The lamina is linear lanceolate flat or slightly rounded, of rather variable size, 8 mm to 2 cm long and 2.5 to 3 mm wide.

General habit

Large vivacious grass growing in loose clumps, shortly rhizomatous. It firstly grows by spreading on the ground, then gets erect and can reach 1 to 2 m in height.

Underground system

Roots are fibrous.

Culm

The culm of the grass is cylindrical, hollow, geniculate ascending or erect, 60 cm to more than 1.5 meters long. It is thick, spongy, reaching 5 to 10 mm in diameter at the base, glabrous, often tinged with purple, with blackish glabrous nodes.

Leaf

The leaves are simple, alternate, with glabrous sheath often purple. The ligule is membranous and short, truncated, ciliated with white hairs at the apex. The lamina is linear, flat or partially folded and then keeled, very variable in size, 7 to 40 cm long and 3 to 15 mm wide. The base is widened, rounded to cordate, the apex elongated acuminate. The faces are glabrous or sparsely hairy, the margin is entire, and scabrous.
 
Inflorescence
 
The inflorescence is a panicle, 15 to 50 cm long, quite often contracted, erect and close branches, or more ample and with spreading branches. Those of the base are slightly reflexed. The branches are solitary or more or less close together and sub-verticillate, filiform, scabrous, those at the base are undivided on a certain part of their length, up to 20 cm long. They are terminated by short racemes of 2 to 3 spikelets applied against the axis.

Spikelet
 
The spikelets are held on a short stalk, 0.5 to 3 mm long. The spikelet is oval lanceolate, slightly compressed, acute to acuminate at the top, 2.5 to 3.5 mm long, glabrous, greenish yellow or stained purple. The glumes are unequal, the lower is short, 1/4 to 1/3 of the length of the spikelet that embraces the base, with one or three ribs. The upper glume is of the size of the spikelet, acuminate, with 7 or 9 protruding ribs. The lower flower is void, with the lemma similar to the upper glume. The external fertile flower is significantly shorter than the spikelet, 2 to 2.2 mm long, oblong to elliptical, a little acute at the apex, with crustaceous smooth and shiny lemma and palea.

Grain

Grain oblong, 1.5 mm long.