They can be evergreen or deciduous perennials that grow from basal underground corms. The alternate leaves are cauline and ensiform (sword shaped). The blades are parallel-veined. The margin is entire. The corms form in vertical chains with the youngest at the top and oldest and largest buried most deeply in the soil. The roots of the lowermost corm in a chain are contractile roots and drag the corm deeper into the ground where conditions allow. The chains of corms are fragile and easily separated, a quality that has enabled some species to become invasive and difficult to control in the garden.