Rhizomatous perennials, bisexual or monoecious. Culms herbaceous to somewhat lignified, erect. Leaf blades broad, with pseudopetioles, ligules membranous or a fringe of hairs. Inflorescences branched or unbranched, the floral units subtended by bracts. Perianth green to brown or absent. Stamens 6; style branches and stigmas 3. Pollen monoporate, with an annulus, with channels in the exine, lacking scrobiculi. Ovule 1. Embryo lateral, differentiated with clear root and shoot meristems enclosed by sheaths (coleorhiza and coleoptile), several embryonic leaves, and a lateral haustorial organ (scutellum). Fruit indehiscent, with one seed, the seed coat fused to the inner wall of the pericarp, the hilum linear. Mesophyll with fusoid cells and cells with invaginated cell walls, midrib complex. Epidermis with multicellular microhairs, with alternating long and short cells, the short cells developing silica bodies. Photosynthetic pathway C3.