Epilobium parviflorum aka Smallflower Hairy Willowherb

Epilobium parviflorum, or hoary willowherb, belongs to the Onagraceae family. This perennial grows wild in Britain and Ireland. Its native range spans Europe, North Africa, and parts of Asia. It reaches India, with records also extending into China. Wild plants grow along streams, in marshes, and in fens. These damp places give a guide to its garden needs.

Plants form clumps with upright stems and fine hairs. Leaves grow along the stems, and some persist through winter. The plant often spends winter as a low leaf rosette. Garden plants reach about 1.6–3.3 feet [0.5–1 metre] tall. The RHS describes a height near 2.5 feet [0.75 metres]. Spread ranges from 0.3–1.6 feet [0.1–0.5 metres]. Plants take two to five years to reach full size. The leafy stems give the plant an upright form in summer.

Small, pale pink flowers appear during summer. Each flower has a long, tube-shaped ovary beneath it. This develops into a pod as the seeds ripen. The pods split open and free the seeds. Silky hairs help the wind carry them away. This lets the plant spread into new sites with ease. Removing spent flowers can limit the number of seedlings. The plant needs no other routine pruning.

Grow it in full sun or part shade. Both clay and loam suit it, across acid to alkaline soils. It accepts moist soil with good or poor drainage. Its wild habitats include ground that stays wet. The RHS gives it an H7 hardiness rating. This covers cold below −4°F [−20°C] under UK growing conditions. It suits exposed sites as well as sheltered ones. No single garden aspect is needed for it to grow.

Hoary willowherb suits wildlife gardens, wildflower meadows, and bog gardens. Its leaves feed elephant hawkmoth caterpillars and those of other moths. It can appear uninvited in gardens through wind-carried seed. Pests rarely cause trouble, and disease is not a major problem. Rust and powdery mildew can occur. PFAF lists the raw leaves as food for salads. It reports no known hazards, but gives no specific pet-safety assessment. The same source lists no known medicinal or other uses.