hairy panicgrass (tapered rosette grass)
Dichanthelium acuminatum (Sw.) Gould & C.A. Clark

Three subspecies below, click thumbnail to see larger image

western panicgrass
Dichanthelium acuminatum subsp. implicatum (Scribner) Freckmann & Lelong


tapered rosette grass
Dichanthelium acuminatum subsp. fasciculatum (Torr.) Freckmann & Lelong


Lindheimer panicgrass
Dichanthelium acuminatum subsp. lindheimeri (Nash) Freckmann & Lelong


Hairy panicgrass is widespread in Iowa except in the western two tiers of counties where it is recorded only from Harrison and Sioux Counties. This species can be found in thin woods, moist meadows, and low prairies and it is rare to common. Its range extends from south-central Canada to the midwestern and northeastern U.S. and it is also found in the western U.S. Like other species of Dichanthelium, hairy panicgrass is characterized by two distinct blooming periods. The conspicuous primary flowering heads are terminal to the culms and are produced in June and early July. Fruiting begins in mid-June, and spikelets begin to drop in late June. Secondary flowering heads are produced from the leaf axils from July through September. The primary flowering heads usually have a lower seed set than the secondary ones, which have flowers that remain closed and are self-pollinated.

Hairy panicgrass is a tufted perennial with usually long-hairy stems with tufts of hairs at the nodes. The leaf sheaths are usually hairy, and the leaf blades are sparsely hairy above and hairy below although occasionally they lack hairs. Hairy panicgrass is considered taxonomically difficult due to extensive variation in leaf hairness and leaf dimensions, and it also crosses with several other species of Dichanthelium. This species is considered to be most similar to stiff-leaved panicgrass (Dichanthelium ovale), but differs from it in having shorter spikelets and hairs on the leaves no more than 3 mm long.

Several subspecies are recognized within hairy panicgrass, and of these three occur in Iowa: subsp. fasciculatum, subsp. implicatum, and subsp. lindheimeri. The latter subspecies, known as Lindheimer’s panicgrass, is perhaps the easiest to recognize and is sometimes considered to be a good species. Unlike the rest of the subspecies in Iowa, Lindheimer’s panicgrass has at least the upper leaf sheaths completely smooth, without any hairs, but often all of the sheaths lack hairs. In addition, the leaves are smooth above and either smooth or softly hairy below. This subspecies is found only in the eastern third of Iowa. and it is usually rare on sandy or gravelly soils where it occurs. The other two subspecies have hairy sheaths and the leaves are smooth or hairy above and always hairy, usually densely so, below. Subsp. fasciculatum has wider leaves (6-12 mm wide) and slightly longer spikelets (1.5-1.8 mm) than subsp. implicatum, which has leaves 2-6 mm wide and spikelets 1.3-1.6 mm long. The leaves of subsp. implicatum are always hairy on both surfaces. Both of these subspecies cover the range of the species in Iowa, but subsp. implicatum is the more common and widespread.

Etymology: : Dichanthelium from the Greek di = twice and anth = flowering, referring to the occurrence of two distinct flowering periods; acuminatum from the Latin acuminatus = having a gradually diminishing point, a reference to the leaf shape.

Plants Plants perennial, densely tufted. Culms usually 15-75 cm, slender, more or less erect to spreading; nodes more or less densely hairy (smooth in subsp. lindheimeri); internodes usually hairy. Fall phase branching extensively from the lower and middle nodes, with conspicuous, fan-shaped fascicles of branches and reduced blades. Basal rosettes usually well differentiated. Leaves along the culms with sheaths shorter than the internodes, the lower sheaths usually covered in soft, distinct, thin hairs, the upper sheaths often short-pubescent with hairs of less than 3 mm, but smooth in subsp. lindheimeri; blades 2-11 cm long, 2-12 mm wide, often yellowish-green, usually hairy above but sometimes smooth, usually hairy below, sometimes densely so, margins often with warty-based hairs near the base, the base rounded or almost heart-shaped. Primary flowering heads terminal, borne above the leaves, 3-10 cm long, 2-6 cm wide, egg- or pyramid-shaped in outline, branches spreading. Spikelets 1.3-1.8 mm long, 0.6-1 mm wide, usually obovoid, shortly hairy; lower glumes 0.4-0.7 mm long, usually 1/3 as long as the spikelet, more or less triangular; upper glumes and lower lemmas usually subequal, about as long as the upper florets at maturity. Chromosome number 2n = 18.

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