Astilbe rivularis aka Tall False Buck's Beard

Astilbe rivularis is a clump-forming perennial in the Saxifragaceae family. Its common name is waterside astilbe. Its native range runs from the Himalaya to central China and Indo-China. It also grows naturally in Borneo and Java. Kew lists it as a plant of temperate climates. It is not native to Britain or Ireland.

The plant forms a large clump of divided green leaves. Bronze tones tint the foliage, which falls away each year. The RHS describes plants reaching about 6 feet [1.8 metres]. Its broader garden height range is 5–8 feet [1.5–2.5 metres]. Spread reaches about 1.6–3.3 feet [0.5–1 metre]. Plants take two to five years to reach their mature size. The leaves form a bold mass beneath the summer flowers. Large sprays of greenish-white blooms arch above the foliage. Their pale colour contrasts with the green and bronze leaves.

Grow this species in soil that holds moisture through summer. It suits moist ground and can also grow in boggy soil. The RHS lists both clay and loam as suitable soils. It accepts acid, neutral and alkaline conditions. Drainage may range from moist but well-drained to poorly drained. Give it dappled shade or a site with indirect sun. The RHS also lists full sun among possible positions. Yet its care notes warn that hot sun can cause damage. This plant does not tolerate drought. Choose a sheltered site rather than an exposed position.

Its need for damp ground makes it useful beside water. The RHS also suggests flower beds and borders. Its large form suits planting for shape and structure. Cottage gardens and informal schemes are other listed uses. The RHS gives this species a UK hardiness rating of H4. That rating covers minimum temperatures of about −10 to −5°C. Local shelter and growing conditions still matter when choosing a site.

Divide plants in late winter or early spring to propagate them. Keep the divisions under glass, then plant outside in late spring. Cut back old stems and leaves before new spring growth starts. The RHS reports few pest problems, though vine weevil may occur. Powdery mildew is another possible problem.