Scape. - One to three feet high, bearing the flowers in whorled, panicled branches. Leaves. - From the root, oblong, lance-shaped or linear, mostly rounded or heart-shaped at base. Flowers. - White or pale pink, small, in large, loose clusters which branch from the scape. Calyx. - Of three sepals. Corolla. - Of three petals. Stamens. - Usually six. Pistils. - Many, on a flattened receptacle.

The water-plantain is nearly related to the arrow-head, and is often found blossoming with it in marshy places or shallow water.