Culms not woody, usually erect, not branched above the base.
Caryopses longitudinally sulcate.
Its taxonomic treatment is contentious, partly because many members are allopolyploids derived from combinations of species that all taxonomists would place in different genera from each other. The large number of natural interspecific and intergeneric hybrids is an additional complication. The intergeneric hybrids are usually completely sterile, but the fertility of interspecific hybrids varies widely. The frequent occurrence of plants exhibiting varying degrees of morphological intermediacy suggest that introgression between some species is not uncommon. The key does not include intergeneric hybrids.