Epilobium ciliatum aka Purple Leaved Willowherb

Epilobium ciliatum has the common name fringed willowherb. It belongs to the evening primrose family. This herbaceous perennial has soft stems and lives for years. Its broad native range spans the Russian Far East. It also spans North America south to Guatemala, and southern South America. The plant grows in marshes, wet meadows, and swamps. It also grows along woodland edges and on rocky cliffs. It has spread beyond its native range, including into Britain.

This plant grows fast and forms upright clumps. It sheds its leaves as the seasons change. RHS gives a garden height of 3.3–4.9 feet [1–1.5 metres]. Its spread reaches about 1.6 feet [0.5 metres]. NC State reports taller plants, reaching 6 feet [1.8 metres]. Stems may stand alone or branch near their tops. They can be green, tan, or flushed with red. They have a somewhat square shape and short hairs above. The green leaves have fine teeth and clear veins. Most lower leaves grow in pairs. They form a basal rosette, a ring at the base. Upper leaves may alternate along the stem. Some leaves have red or purple edges.

NC State gives a June to October bloom time. The small blooms have a trumpet shape. Each has four petals with deep notches. Flowers may be white, pink, or rose-purple. Some have dark veins. They grow from leaf axils near the stem tips. These are the joints where leaves meet stems. Bees, flies, and hummingbirds visit the flowers. The plant also feeds the larvae of butterflies and moths. Long, narrow seed pods, called capsules, follow the blooms. They turn brown, and each has four chambers. Each splits open when dry. Tiny brown seeds bear soft white hairs. These hairs help the wind carry the seeds.

Choose moist soil and a bright site for best growth. The plant can grow in shade and many soil textures. It grows in acid, neutral, and alkaline ground. It also copes with a range of drainage. RHS rates its UK hardiness as H4. NC State lists USDA zones 8a–11b for the species. Plants reach full size within one to two years. They need no routine pruning. They serve as food sources in wildlife gardens and naturalized areas.

Its main drawback is fast spread through its freely formed seed. In good conditions, seedlings can set seed within ten weeks. Plants can be hard to remove once they take hold. It causes problems in nurseries. It soon takes hold on disturbed wet ground. Some regions beyond its native range class it as invasive. Stop seed set to help curb its spread. Serious pests and diseases rarely cause problems. Still, watch for powdery mildew. The supplied sources do not establish edible uses or toxicity.