Panicum dichotomiflorum |
Panicum dichotomiflorum subsp. dichotomiflorum |
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fall panicgrass, fall panicum, knee grass, panic d'automne, smooth witchgrass |
fall panic grass, fall panicum, panic d'automne dressé, panic à fleures dichotom, smooth witchgrass, western witchgrass |
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Habit | Plants annual or short-lived perennials in the Flora region, perennial in the tropics; usually terrestrial, sometimes aquatic but not floating. | |||||||||
Culms | 5-200 cm tall, 0.4-3 mm thick, decumbent to erect, commonly geniculate to ascending, rooting at the lower nodes when in water, simple to divergently branched from the lower and middle nodes, usually succulent, slightly compressed, glabrous; nodes usually swollen, sometimes constricted on robust plants, glabrous; internodes glabrous, shiny, pale green to purplish. |
5-200 cm. |
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Sheaths | compressed, inflated, sparsely pubescent near the base, elsewhere mostly glabrous, sparsely pilose, or hispid, hairs sometimes papillose-based, margins or throat ciliate, with papillose-based hairs; ligules 0.5-2 mm; blades 10-65 cm long, 3-25 mm wide, glabrous or sparsely pilose, often scabrous near the margins, midribs stout, whitish. |
glabrous or sparsely pilose, not hispid with papillose-based hairs. |
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Panicles | 4-40 cm, diffuse, lax, with a few spikelets; branches to 15 cm, alternate or opposite, occasionally verticillate, ascending to spreading, stiff, scabrous; pedicels 1-6 mm, sharply 3-angled, scabrous, expanded to cuplike apices, appressed mostly to the abaxial side of the branches. |
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Spikelets | 1.8-3.8 mm long, 0.7-1.2 mm wide, ellipsoid to narrowly ovoid, light green to red-purple, glabrous, acute to acuminate. |
2.3-3.8 mm, tapered from below the middle to the acuminate apices; upper glumes and lower lemmas subcoriaceous. |
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Lower glumes | 0.6-1.2 mm, 1/4 - 1/3 as long as the spikelets, 0-3-veined, obtuse to acute; upper glumes and lower lemmas similar, exceeding the upper florets by 0.3-0.6 mm, 7-9-veined; lower paleas vestigial to almost as long as the lower lemmas; lower florets sterile; upper florets 1.4-2.5 mm long, 0.7-1.1 mm wide, narrowly ellipsoid, smooth, shiny, stramineous to nigrescent, with pale veins. |
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Pedicels | usually less than 3 mm and shorter than the spikelets. |
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2n | = 36, 54. |
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Panicum dichotomiflorum |
Panicum dichotomiflorum subsp. dichotomiflorum |
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Distribution |
AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; HI; PR; BC; NB; NS; ON; QC
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Discussion | Panicum dichotomiflorum grows in open, often wet, disturbed areas such as cultivated and fallow fields, roadsides, ditches, open stream banks, receding shores, clearings in flood plain woods, and sometimes in shallow water. It is probably native throughout the eastern United States and adjacent Canada, but introduced elsewhere, including in the western United States. Its size and habit may be partly under genetic control, but these features also seem to be strongly affected by moisture levels, soil richness, competition, and the time of germination. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Panicum dichotomiflorum subsp. dichotomiflorum is the most common of the three subspecies and is found throughout the range of the species. In the past, members of this subspecies have been treated as two different taxa, var. geniculatum (Alph. Wood) Fernald and var. dichotomiflorum, with more erect, slender plants having fewer long-exserted panicles with slender, ascending branches and less crowded spikelets being placed in var. dichotomiflorum. Such plants are more common in the southern part of the subspecies' range, but the traits are poorly correlated and the differences are at least in part affected by photoperiod, nighttime temperatures, and the time of seed germination. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 25, p. 469. | FNA vol. 25, p. 469. | ||||||||
Parent taxa | Poaceae > subfam. Panicoideae > tribe Paniceae > Panicum > subg. Panicum > sect. Dichotomiflora | Poaceae > subfam. Panicoideae > tribe Paniceae > Panicum > subg. Panicum > sect. Dichotomiflora > Panicum dichotomiflorum | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Synonyms | P. dichotomiflorum var. geniculatum | |||||||||
Name authority | Michx. | unknown | ||||||||
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