Calamagrostis (reed grass or smallweed) is a genus of flowering plants in the grass family Poaceae, with about 260 species that occur mainly in temperate regions of the globe. Towards equatorial latitudes, species of Calamagrostis generally occur at higher elevations. These tufted perennials usually have hairless narrow leaves. The ligules are usually blunt. The inflorescence forms a panicle. Some may be reed-like.