Onagraceae - Evening Primrose Family
Contents English Names Index

The Evening Primrose or Willow herb family - Onagraceae - comprises about 20 genera and 700 species of annual or perennial plants that live throughout the world. They are mainly herbs, but we also find trees and shrubs. Some genera such as Fuchsia or Oenothera are very valuable in gardening. Most species are found in temperate regions of the New World.
The flowers of this family are usually radially symmetrical, has 4 petals and 4 sepals, mostly separate, and growing in tall or branched clusters. The flower parts are attached at the top of the ovary. Number of stamens are 4 to 8, generally 8 and the pistil is single with a 4-lobed stigma in many cases.
The plants have leaves that are simple, alternate or opposite, without stipules.
The fruits are commonly contained in an long 4-chambered capsule and carry a white tuft of hair for wind dispersal.

Guide to Identify Presented Species of the Evening Primrose Family
Epilobium angustifolium - Fireweed
Perennial, 1-3 m tall, leafy, often in large colonies. Common on roadsides.
Flowers rose-purple to pink, 2-4 cm wide, with 4 broad petals, in tall clusters.
Leaves alternate, numerous, narrowly lance-shaped, stalkless and hairless.
Epilobium ciliatum - Purple-Leaved Willowherb
Perennial, 30-100 cm tall, branched and hairy above. Moist sites.
Flowers rose-purple to white, 5-15 mm wide, erect, with 4 notched petals
Leaves basal and opposite, lance-shaped, 3-7 cm long, shallowly toothed.
Epilobium hornemannii - Hornemann's Willowherb
Perennial, 15-30 cm tall, stems usually simple. Moist sites, montane-alpine.
Flowers rose to violet, 8-12 mm wide, few on stem tops, with 4 notched petals.
Leaves opposite, 1.5-5 cm long, oblong, blunt-tipped, short-stalked.
Oenothera cespitosa - Tufted Evening Primrose
Tufted, almost stemless perennial rarely up to 25 cm tall. Dry, bare hills.
Flowers white to pink, 5-9 cm wide, single from the base, open in the evening.
Leaves basal, oblanceolate, entire or toothed, 10-25 cm long, 1-2.5 cm broad.
Oenothera biennis - Common Evening Primrose
Robust biennial with hairy stems, 30-100 cm tall. Dry, moderately open sites.
Flowers fragrant, bright yellow, 3-4 cm wide, in tall cluster, with 4 broad petals.
Leaves alternate and basal, lance-shaped, numerous, entire to wavy-toothed.
Alphabetical listing with links to presented species of the Evening Primrose family:
Scientific Name English Name Swedish Name


Fireweed, Willowherb
Evening Primrose
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