Willowherbs

Marsh Willowherb Hoary Willowherb Great Willowherb Rosebay Willowherb

What are they?

This is a group of very familiar plants, as willowherbs are common in human-influenced habitats. They form a readily recognisable group of pink-flowered, annual or perennial, herbaceous plants and are members of the Onagraceae family, along with fuchsias, evening-primroses and a number of half-hardy plants grown as ornamentals.

Where are they found?

Our native willowherbs mostly occur on damp soils, but they are also perfectly happy as weeds of waste or disturbed ground and in urban situations. Introduced species are common as garden weeds and in a variety of disturbed soils and urban locations. Rosebay Willowherb is something of an exception in doing best on drier, acid soils on heaths and open embankments, often with Bracken.

Identification

Most willowherbs are readily identified by their paired, opposite leaves, long seed capsules and four-petalled, pink flowers. Rosebay Willowherb is an exception to this in having the leaves arranged spirally and in having elongate, terminal spikes of flowers. Although a 'willowherb' is relatively easy to identify from other plants, telling the various species apart is far less easy - and hybrids are quite common! A combination of characters should be checked as follows: the shape of the stigma (the white, female part at the centre of the flower), the presence or absence of ridges on the stem, the shape of the leaf and whether it has a stalk, the type of hairs on the upper stem and on the seed capsules. While this might seem a lot, each species will show a different combination of these four features and most can be identified fairly easily with practice. Note that Rosebay and Great Willowherbs are tall plants, to 1.5m in height and this great size distinguishes them readily from all of the other species.



Rosebay Willowherb      Chamerion angustifolium

Native in the UK but perhaps only introduced in East Anglia (as a soil stabiliser). Now widespread and common, often forming extensive colonies on heathland and embankments. Often known as 'Fireweed' for its habit of rapidly colonising areas of heathland or railway embankments after they have been burned. Flowers July to September. Easily identified by its long spikes of large flowers which can form impressive and extensive colonies. Leaves alternate not in opposite pairs, often spirally arranged on the hairless stems.

Rosebay Willowherb Rosebay Willowherb Rosebay Willowherb Rosebay Willowherb
Habit
Habit
Flower
Flower
Rosebay Willowherb Rosebay Willowherb Rosebay Willowherb Rosebay Willowherb
Flower
Leaves
Upper stem
Seedheads


Great Willowherb      Epilobium hirsutum

Native in ditches and most types of damp places and waterlogged soils. Flowers July to August. A tall species, to 1.5m in height and forming large, spreading colonies. Basal leaves in the spring are hairless but later stem leaves are silky hairy, giving them a hoary look. Upper stems densely hairy, rounded and not ridged. Stigma four-lobed, spreading; petals much broader than those of other species.

Great Willowherb Great Willowherb Great Willowherb Great Willowherb
Habit
Habit
Flowers
Flower
Great Willowherb Great Willowherb Great Willowherb Great Willowherb
Basal leaves
Stem leaves
Upper stem
Seedheads


Hoary Willowherb      Epilobium parviflorum

Native and common in damp places as well as a weed of disturbed and urban environments. Flowers July to August. Grows to 100cm but typically much less. Leaves silky hairy, giving them a hoary look; untoothed margins and no (or less than 3mm) leaf stalk. Stems densely hairy, rounded and not ridged. Stigma four-lobed, with the lobes clustered together and not spreading.

Hoary Willowherb Hoary Willowherb Hoary Willowherb Hoary Willowherb
Habit
Habit
Flowers
Flower
Hoary Willowherb Hoary Willowherb Hoary Willowherb
Leaves
Leaves
Seedheads


Broad-leaved Willowherb      Epilobium montanum

Native in damp, often shady places as well as a weed of disturbed and urban environments. Formerly the most common willowherb as a garden weed but now more often replaced by Fringed Willowherb. Flowers June to August. Leaves broadly rounded at the base with strongly toothed margins and a short (2-6mm) leaf stalk. Stems with a mixture of short, straight hairs and, short, curled hairs; stems rounded and not ridged. Stigma four-lobed, with the lobes clustered together and not spreading.

Broad-leaved Willowherb Broad-leaved Willowherb Broad-leaved Willowherb
Habit
Flowers
Flower
Broad-leaved Willowherb Broad-leaved Willowherb Broad-leaved Willowherb
Leaves
Leaves
Stem


Fringed Willowherb      Epilobium ciliatum

(American Willowherb) Introduced from North America and now very common as a weed of disturbed and urban environments. Flowers June to August. Leaves rounded at the base with lightly toothed margins and a short (1.5-5mm) leaf stalk. Stems with a covering of glandular hairs, particularly towards the top; stems two-ridged near the base, becoming two- or four-ridged at mid stem and rounded towards the top. Stigma club-shaped. Petals pink but often very pale, whitish.

Fringed Willowherb Fringed Willowherb Fringed Willowherb Fringed Willowherb
Flowers
Flower
Basal leaves
Stem leaf
Fringed Willowherb Fringed Willowherb Fringed Willowherb Fringed Willowherb
Lower stem
Mid stem
Upper stem
Seed capsule


Square-stalked Willowherb      Epilobium tetragonum

Native and very common as a weed of cultivation, especially on heavier soils. Common in arable landscapes and along roadsides and tolerant of quite dry conditions. Flowers July to August. Leaves long-lanceolate, rounded at the base with toothed margins and no leaf stalk. Stems with a covering of stiff hairs, flattened against the stem; stems two-ridged near the base, becoming four-ridged at mid stem. Stigma club-shaped. Flattened hairs continue onto the seed capsules.

Square-stalked Willowherb Square-stalked Willowherb Square-stalked Willowherb Square-stalked Willowherb
Habit
Flower
Stem leaf
Stem leaf
Square-stalked Willowherb Square-stalked Willowherb Square-stalked Willowherb
Mid stem
Mid stem
Seed capsule


Short-fruited Willowherb      Epilobium obscurum

Native. Widespread but generally uncommon in a range of damp, often shady, habitats. Flowers July to August. Leaves elliptic-lanceolate, rounded at the base with weakly toothed margins and no leaf stalk. Stems with a covering of stiff hairs, flattened against the stem; stems typically four-ridged at mid stem. Stigma club-shaped. Flattened hairs continue onto the seed capsules but there are also glandular hairs at the top of the seed capsule and on the sepals.

Short-fruited Willowherb Short-fruited Willowherb Short-fruited Willowherb Short-fruited Willowherb
Habit
Flower
Flower
Stem leaf
Short-fruited Willowherb Short-fruited Willowherb
Seed capsule
Upper seed capsule and sepals


Marsh Willowherb      Epilobium palustre

Native. Widespread but generally uncommon in better-quality, wetland habitats. Flowers July to August. Leaves narrowly lanceolate with untoothed, downturned margins and a short stalk. Stems rounded with a covering of short and curled hairs. Stigma club-shaped. A distinctive species in its long leaves and gracefully arching upper stems.

Marsh Willowherb Marsh Willowherb Marsh Willowherb Marsh Willowherb
Habit
Habit
Flower
Flower
Marsh Willowherb Marsh Willowherb Marsh Willowherb Marsh Willowherb
Leaves
Leaf underside
Mid stem
Upper stem


Pale Willowherb      Epilobium roseum

Native. Widespread but rare in a variety of wet habitats as well as an occasional urban weed. Flowers July to August. Leaves broad with toothed margins but tapered (not rounded) at the base and with a long stalk (4-14mm). Lower stems 2-ridged (sometimes 4-ridged), upper stems rounded with a covering of glandular hairs. Stigma club-shaped. A distinctive species in its long-stalked, rounded leaves and pale flowers.

Pale Willowherb Pale Willowherb Pale Willowherb
Flowers
Flower
Flowers
Pale Willowherb Pale Willowherb Pale Willowherb
Leaf
Leaf stalk
Upper seed capsule and sepals


Hybrid Willowherb      Epilobium x floridulum

Native. Hybrid willowherbs are not common but are frequently encountered if searched for. Most species may hybridise with each other where they occur together and can usually be deduced by their mixed combination of characters from the parents. Flowers July to August. The photos here show the hybrid between Hoary and Fringed Willowherbs as an example of a typical hybrid. The plant shows a mixture of hairs from both parents, with lower stem hairs being simple and upper stem hairs being a mix of simple and glandular hairs. The leaves are intermediate in shape and hairiness.

Hybrid Willowherb Hybrid Willowherb Hybrid Willowherb Hybrid Willowherb
Flower
Stem leaf
Lower stem
Upper stem


Tall Annual Willowherb      Epilobium brachycarpum

Introduced from Western North America and first recorded around Colchester in 2004, where it is increasing steadily. First recorded in Norfolk with new plantings along the Northern Distributor Road in 2019. Likely to spread along roadsides and in newly planted areas where soil or mulch is brought in. Flowers July to August. A very different plant to any of our native species. Annual, not perennial, stems from 60cm to over a metre in height, much branched with wiry, spreading branches and small leaves. Flowers small (5-6mm across) with deeply divided petals. Seed capsules flattened in one plain and broad in the other, often slightly curved.

Tall Annual Willowherb Tall Annual Willowherb Tall Annual Willowherb Tall Annual Willowherb
Habit
Habit
Flower
Flower & seed capsule
Tall Annual Willowherb Tall Annual Willowherb Tall Annual Willowherb
Leaves
Leaves
Seed capsule