Panicum alatum var. minus

Zuloaga and Morrone 1996, FNA 2003

Common Name: winged panicgrass Duration: Perennial Nativity: Native Lifeform: Graminoid General: Cespitose annual grass, 15-100 cm tall, tinted purplish; stems geniculate to erect, compressed at the base, branching at the lower nodes; nodes glabrous to short-pilose. Vegetative: Sheaths glabrous to hirsute, the margins papillose-hairy, at least distally; ligules membranous- ciliate, 0.7-1.8 mm; blades 2-18 cm long, 0.5- 1.5 mm wide, more or less erect to ascending, flat, glabrous or with sparse hairs on the lower surface. Inflorescence: Panicles lax, diffuse, to 25 cm long; primary branches spreading; secondary branches and pedicels appressed; spikelets ellipsoid, 3 mm long, tinted purple, and 2-flowered, the first floret reduced to a sterile lemmas and the second floret fertile; lower glume 1/2 to 3/4 the length of the spikelet; upper glume and sterile lemma similar to each other, 2.5 mm and 7-9 nerved; fertile lemma indurate, obovoid at maturity, 1.5 mm, straw colored to brown, pubescent, 7-nerved, short-stipitate, with a pair of fleshy elaiosomes at the base; caryopsis ovoid, 1 mm, beige. Ecology: Found in sand to clay soils and along roadsides, below 6,000 ft (1829 m); flowers August to September in the US southwest. Distribution: s AZ, south through MEX and C. Amer. to Venezuela and the Galapagos Islands. Notes: Panicum alatum is apparently identical to P. hirticaule except that the fertile floret has a pair of eleiosomes at the base, which are fleshy structures used to attract ants to aid in seed dispersal. This is not a useful field character, as the elaiosomes are not particularly obvious even under a dissecting scope. To confirm ID on any annual Panicum in the P. hirticaule group, it is advisable to make a proper collection that includes mature reproductive material. There are 3 varieties of P. alatum. The most common in our area is P. alatum var. minus which has spikelets 2.4 to 3 mm long, and seeds that are smooth and shiny. Ethnobotany: Seeds were used as a grain. Etymology: Panicum is the Latin name for millet; alatum means winged, referring to the pair of elaiosomes at the base of the seed; and minus means smaller. Synonyms: Panicum hirticaule var. minus, Panicum hirticaule var. majus Editor: AHazelton 2015