The sedges are a family of grass-like or rush-like perennials with unstalked linear leaves, sometimes reduced to a sheath. The flowers, generally grouped into spikelets, are tiny, with petals and sepals reduced to a bristle. Several male and female flowers on the same stalk may form a spike. There are about 120 genera and 5,000 species. Sedges can be told from grasses by their solid, often three-sided, unjointed stems. They typically grow on poor acid soils and have little nutritional or economic value.