Plants perennial; strongly rhizomatous. Culms 10-150(217) cm, mostly erect and unbranched, usually with 3-4 nodes. Leaves not aromatic; sheaths open, ciliate at the margins of the collars; ligules membranous; blades of the basal leaves linear to lanceolate, sometimes ciliate basally, those of the cauline leaves reduced. Inflorescences terminal, cylindrical to conical panicles with an evident rachis; rachises often with numerous long hairs; inflorescence branches 1-7 cm, usually shorter than the rachises, with spikelets in unequally pedicellate pairs; disarticulation below the glumes. Spikelets homogamous and homomorphic, unawned; calluses very short, hairy, hairs 7-16 mm. Glumes equal to subequal, membranous, 3-9-veined, with hairs longer than the florets over at least the lower 1/2; lower florets reduced to hyaline or membranous lemmas; upper florets bisexual, lemmas, if present, hyaline, unawned; anthers 1-2, yellow to brown; stigmas elongate, purple to brown; styles connate or free. Pedicels not fused to the branch axes, terminating in cuplike tips. Caryopses ovate to obovate, light to dark brown. x = 10. Named after Ferrante Imperato (1550-1625) of Naples, an apothecary and author of a folio work on natural history.