Perennials, tufted, shoots extra- or intra-vaginal. Leaf sheath margins usually free, rarely connate, sometimes with auricles; leaf blades folded to conduplicate and filiform, sometimes flat; ligule membranous. Inflorescence an open, contracted or spikelike panicle. Spikelets with 2 to several florets, uppermost floret usually reduced; rachilla usually scabrid, rarely smooth or pubescent; disarticulating above glumes and between florets; glumes usually unequal, herbaceous to scarious, rarely subleathery, lower glume often small, 1-veined, upper glume usually shorter than lowest lemma, 3(–5)-veined; lemmas usually similar in texture to glumes, often subleathery at least with age, usually ± laterally compressed but not keeled, rounded on back at least toward base, usually 5-veined, veins sometimes prominent, apex acuminate, entire or notched, awned or awnless; palea subequal to lemma, keels scabrid, rarely smooth. Stamens 3. Ovary glabrous or hairy on top. Caryopsis oblong or linear, usually ventrally sulcate, usually free from lemma and palea, hilum long-linear. x = 7.

Many of the species are superficially very similar, particularly among the fine-leaved species. In these, the position of sclerenchyma tissue, as seen in a cross section of the leaf blade, is an important aid to identification. The type of branching of the basal vegetative shoots (tillers) is also important. If the shoot breaks through the base of the subtending leaf sheath a loose tuft results (extravaginal branching), but if it grows up inside the leaf sheath a denser tuft results (intravaginal branching).

The fine-leaved species include a number of species aggregates. The aggregate name has been used in the main key, as this will be sufficient for most users. Within the aggregates individual taxa are recognized either at specific or infraspecific rank, but the differences between the taxa are slight and often overlapping.

This large genus is divided into subgenera, which are indicated in the key. Recent molecular work is indicating that the larger broad-leaved species are not closely related to the fine-leaved species.

Most of the species provide good grazing, and some are important constituents of fine lawns.

About 450 species:temperate regions throughout the world, extending into the tropics on mountain tops; 55 species (25 endemic) in China.

(Authors: Lu Shenglian (卢生莲), Chen Xiang (陈翔); Susan G. Aiken)