Panicum philadelphicum
Panicum hemitomon
panic de philadelphie, Philadelphia panic grass, Philadelphia witchgrass
maidencane, mountain panic
8-100 cm tall, about 1 mm thick, erect to decumbent, simple to profusely branched;
nodes sparsely to densely pilose.
50-200 cm, mostly erect and sterile, glabrous, often rooting from the lower nodes if submerged.
usually glabrous, or pilose or hirsute at the lowermost sheath, especially distally;
ligules shorter than 1 mm;
blades 8-35 cm long, 5-15 mm wide, ascending or spreading, abaxial surfaces glabrous, adaxial surfaces usually scabridulous or pubescent, bases slightly narrowed, margins scabrous, apices long-tapering.
often crowded basally;
sheaths rounded, usually longer than the internodes, hispid, hairs papillose-based, to 5 mm;
ligules 0.5-1.5 mm;
blades 3-30 cm long, 2-12 mm wide, linear, ascending to erect, flat, hirsute to sparsely pilose, greenish or purplish, bases truncate to subcordate and ciliate on the margins, apices acute.
7-27 cm long, 4-24 cm wide, 1/4 - 1/3 as long as the plants, diffuse, usually exserted at anthesis, not breaking at the base of the peduncles to become a tumbleweed;
rachises glabrous or sparsely pilose basally;
primary branches spreading, secondary branches and pedicels confined to the distal 2/3 secondary branches diverging to appressed, with 1-4 spikelets;
pedicels 3-15 mm, spreading to appressed, scabrous or hirsute;
pulvini glabrous or pilose.
10-30 cm long, less than 1 cm wide;
branches mostly short, appressed-ascending, with fascicles of congested spikelets; ultimate branchlets 1-sided;
pedicels 0.2-1.8 mm.
1.4-2.4 mm long, 0.5-0.7 mm wide, usually green, glabrous.
2-2.8 mm, subsessile, lanceoloid, slightly laterally compressed, glabrous, acute.
0.5-0.9 mm, usually less than 1/2 as long as the spikelets, 3-4-veined, truncate to acuminate;
upper glumes 1.6-2 mm, 7-veined, veins not prominent;
lower lemmas 1.6-1.9 mm, 7-9-veined, veins not prominent;
lower paleas absent;
lower florets sterile;
upper florets 1.5-1.7 mm long, about 0.4 mm wide, often dark brown, sometimes disarticulating, apices minutely papillose.
about 1/2 as long as the spikelets, slightly keeled along the midveins, 3-veined, acute;
upper glumes and lower lemmas similar, glumes slightly shorter than the lemmas, faintly keeled on the back, acute;
lower florets staminate;
lower paleas subequal to the lower lemmas;
upper florets 2-2.5 mm, 2/5 to almost as long as the spikelets, narrowly ellipsoid;
upper lemmas relatively thin, flexible, pale, acuminate, clasping the paleas only at the base.
= 18.
= 36, 40.
Panicum philadelphicum
Panicum hemitomon
Panicum philadelphicum grows in open areas such as fallow fields, roadside ditches, receding shores, and rock crevices. It is restricted to the eastern part of the Flora region. It intergrades with P. capillare, possibly as a result of hybridization, especially in the southeastern United States. Seeds germinating on receding shores in late summer often produce tiny plants.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Panicum hemitomon forms extensive, nearly pure stands in water or wet soils such as marshes, swamps, and along the shores of streams, canals, ditches, lakes, and ponds. It is restricted to the United States.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Spikelets less than 1/2 as wide as long; plants purplish | subsp. lithophilum |
1. Spikelets usually more than 1/2 as wide as long; plants green or yellow-green. | → 2 |
2. Spikelets 1.9-2.4 mm long; apices of the upper glumes and lower lemmas straight; secondary branches and pedicels divergent; blades often 6-12 mm wide, those of the flag leaves usually more than 1/2 as long as the panicles | subsp. gattingeri |
2. Spikelets 1.4-2.1 mm long; apices of the upper glumes and lower lemmas curving over the upper florets at maturity; secondary panicle branches and pedicels appressed; blades usually 2-6 mm wide, those of the flag leaves usually less than M as long as the panicles | subsp. philadelphicum |
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