Rhizomatous perennials, growing in fresh water, with 6-petalled pink or white flowers and narrow foliage. Leaves triangular in cross-section and apparently unpalatable to cattle, hence the latin name, from Greek bous, 'cow' and temno, meaning 'to cut'.
B. umbellatus is a beautiful native plant of shallow, still and slow-moving water bodies, the flowers seem to be especially attractive to hoverflies and other flies. Those visitors are in a prime location to become prey for insect predators such as dragonflies and damselflies, the nymphal stages of which find refuge at the base of the emergent stems and indeed use those stems to haul themselves out of the water before becoming adult.