Genus with around 70 rhizomatous perennials with impressive foliage. Some species have a clumping growth habit and these tend to have very large leaves, whereas other species have smaller leaves and tend to grow in a mat-forming manner. Foliage is rounded to oval to heart-shaped and normally strongly lobed and toothed at the edges. These are often placed by water edges and can provide architectural structure to a garden. Some species are favoured for their small green-yellow flowers, produced abundantly on thick, brushy spikes.