- Name also: Evening Star, Common Evening-primrose
- Family: Willowherb Family – Onagraceae
- Growing form: Biennial herb. Taproot stout.
- Height: 40–60(–100) cm (15–25(–40) in.). Stem hairy, green (sometimes reddish).
- Flower: Corolla regular (actinomorphic), yellow (sometimes reddish), approx. 2–3 cm (0.8–1.2 in.) long; petals four, 25–30 mm (1–1.2 in.) long. Sepals 4, narrowly triangular, recurved. Stamens 8. Pistil formed from two fused carpels, stigma 4-lobed. Inflorescence a spiked raceme. Flowers fragrant.
- Leaves: In basal rosette and alternate on stem. Rosette leaves long-stalked, wither during flowering time, stem leaves short-stalked. Rosette leaves’ blade ovate–narrowly elliptic, stem leaves’ blade elliptic–narrowly ovate, small-toothed–with entire margins.
- Fruit: Narrow, round, blunt-edged capsule, 25–35 mm (1–1.4 in.) long, hairy when young, with 4 capsules.
- Habitat: Gardens, graveyards, railwaysides, roadsides, harbours, wasteland, rubbish tips.
- Flowering time: July–August.
Almost all the primroses are native to North America. Evening primrose’s ancestors also travelled from North America to Europe, but proper speciation probably didn’t happen until after this. Primroses are interesting from the point of view of genetics, but they are also popular in gardens thanks to their wonderful yellow flowers and long flowering time. Evening primrose is a nocturnal plant whose corolla opens in the evening and closes in the morning – many other primroses only open in bright sunshine and close up for the night. Evening primrose attracts different kinds of night butterflies such as hawk moths and bees too. Finches readily eat its and other primrose’s seeds. Primrose spreads easily through its seeds in inhabited areas and it can also be found in the wild wasteland brought by traffic.
Primrose’s useful qualities were known already to Native Americans who used it to treat wounds and bowel problems. Nowadays evening primrose has become a leading medicinal plant. Its seeds are pressed to release the oil which has a positive influence on heart and vascular diseases, and tests on its effectiveness in treating MS are also promising. Evening primrose’s leaves are edible and traditionally have been used as a leaf vegetable. In some countries evening primroses is classified as an invasive weed.
Red-stalked Evening Primrose
Oenothera muricata (Oenothera rubricaulis)
Apart from evening primrose, related plants that can be found in and around Finnish gardens include red-stalked evening primrose, which was previously classed as the same species as evening primrose. Other possible primrose species include hairy evening primrose (O. depressa) and large-flowered evening primrose (O. glazioviana, also known as redsepal evening primrose). Differentiating between different primrose species is generally difficult, and a number of other species and hybrids grow casually in Finland.