Butomus umbellatus aka Flowering Rush

Butomus umbellatus, or flowering rush, belongs to the Butomaceae family. It is a perennial that grows at water margins. Its native range spans temperate Eurasia and reaches parts of India. It also includes northwest Africa, Britain, and Ireland. Wild plants grow beside ponds, ditches, and canals. They favour open sites rather than shade.

Garden plants reach 3.3–4.9 feet (1–1.5 metres) in height. Their spread ranges from 0.3–1.6 feet (0.1–0.5 metres). Plants take two to five years to reach full size. The tufted growth has a rush-like look. Upright, twisted leaves give the plant its grassy form. The leaves show bronze-purple tones as they grow, then become dark green. This deciduous plant loses its foliage each year. Stiff stems carry the flowers above the leaves.

The flowers form umbels and open in late summer. Each pink flower measures about 0.8 inches (2 centimetres) across. The blooms have a scent. Their colour contrasts with the plant's dark green leaves. Flowering rush suits pond edges and bog gardens. It also fits wildlife gardens and loose, informal planting schemes. Its main garden use is as a waterside ornamental. Both the flowers and upright foliage contribute to that role.

Grow it in full sun and fertile mud. Pond margins suit it, as does shallow standing water. Water can reach 0.8 feet (0.25 metres) deep. It accepts clay, loam, or sand when the ground stays wet. Acid, neutral, and alkaline soils all suit it. RHS rates its hardiness H5; PFAF lists USDA zones 4–8. Cut the plant back once flowering ends. Sow seed when ripe, or divide rhizomes in spring. Water lily aphids may attack, though diseases seldom cause trouble. PFAF flags weed potential, so consider its spread when choosing a site.

PFAF lists the roots and seeds as edible. Cook the tubers after peeling them and removing small rootlets. Dried roots can provide flour or thicken soups. They contain more than half their weight in starch. The seeds are small and awkward to handle. PFAF reports no known hazards, but this is not proof of safety in every use. It lists no known medicinal uses.