Perennial herbs. Culms triangular or rarely rounded. Leaves with prominent long leaf sheaths. Inflorescence usually composed of several cylindric spikes but (in spicato-paniculata) consisting of 1-2 pyramidal panicles arising from upper leaf sheaths. Flowers unisexual, in unisexual or bisexual spikes. In this genus, in addition to the normal glume subtending the flower, the female flowers are enclosed within a utricle, which is beaked above and broad below and hence shaped something like a bottle. Ovary with 2-3 stigmas protruding from the beak at the tip of the utricle. Male flowers with usually 3 stamens.