- Name also: Hairy Willow-herb, Great Willowherb, Great Hairy Willowherb, Codlins and Cream (USA)
- Family: Willowherb Family – Onagraceae
- Growing form: Perennial herb. Subterraneous runners white, thick, up to 20 cm (8 in.) long.
- Height: 50–150 cm (20–60 in.). Stem usually branched, round, with straight and glandular hairs all over.
- Flower: Corolla regular, purple, approx. 2–3 cm (0.8–1.2 in.) wide; petals 4, with notched tips. Sepals 4, densely covered with glandular hairs, sparsely straight-haired at tip. Stamens 8. Pistil formed from two fused carpels, stigma 4-lobed; ovary under tepals, densely covered with glandular hairs, sometimes also with straight hairs. Inflorescence a lax, leafy raceme.
- Leaves: Opposite (alternate in inflorescence), stalkless, semi-amplexicaul. Blade narrowly elliptic, largely and densely toothed, densely hairy.
- Fruit: Tubular, 4-valved, 6–9 cm (2.4–3.6 in.) long capsule. Seeds granular, plumed.
- Habitat: Ditches, shores, railway embankments, wasteland.
- Flowering time: July–August.
Besides rosebay willowherb (E. angustifolium), hairy willowherb represents the large end of Finland’s range of Willowherb family. This handsome specimen grows up to 1.5 m (60 in.) high with an abundantly branching stem and a crown that can almost disappear beneath a wonderful display of pink and purple flowers. Hairy willowherb’s flamboyance is only enhanced by its habit of forming a dense pure stand covering several square metres. At least half the plants have grown to their full height by June, and the flowering time is often towards the end of the summer, clearly later than other willow-herbs. Seeds that germinate in the spring seldom make any flowers in their first summer.
Hairy willowherb is a European species but it’s not native to Finland. It was first found growing in Finland in 1886 in Turku’s harbour area. There was an abundance of sightings over the following century and especially in the 1960s the species was more numerous and widespread. There are still plenty clay valleys, which suit the species well, uninhabited all over Finland. Hairy willowherb has expanded its habitat with the help of people, often spreading to dwelling centres and from busy hubs towards the countryside. The species stays within areas that people influence and doesn’t move into totally wild areas. Hairy willowherb is completely established in its old habitats, but pioneer stands are often short-lived. Its large size and stout basal structure make hairy willowherb a relatively strong competitor which is able to hold its own once it has settled down there.
Small-flowered Willowherb (Smallflower Hairy Willowherb)
Another eye-catching hairy willowherb species grows wild in Finland: small-flowered willowherb, which is native to south and south-west Finland. It has smaller flowers and a shorter stem than hairy willowherb, and its hair covering is solely comprised of straight hairs. Small-flowered willowherb is clearly rarer than hairy willow-herb: it grows quite commonly only on the Åland Islands and in Lohja on the mainland.