Oenothera tetragona - Evening Primrose

Oenothera tetragona or Square-stemmed Evening Primrose is a vibrant perennial that produces numerous ephemeral flowers in a bright yellow colour during the summer. Widely used in European gardens, it is an essential plant for flower gardens. It is ideal for borders or as a standalone plant.

Originally from eastern North America, it was imported as a medicinal plant through the Evening Primrose (Oenothera biennis).

The Square-stemmed Evening Primrose is a charming perennial with a spreading habit, composed of upright stems reaching 30 to 40cm (12 to 16in) in height and 40cm (16in) in width. Its reddish-green stems bear bluish-green leaves in spring, lanceolate in shape with dentate margins. At the base of the stem, the leaves are arranged in a rosette and spiral alternately along the stem, almost pedunculate at the top. At the top of the stems, clusters of 70cm (28in) in height, composed of large ephemeral flowers, appear during the months of July to August. Its loose flowers display reddish buds that open up, for a day, into bright yellow flowers carried by reddish sepals. Although its flowers bloom at dawn and wither at dusk, its generous flowering can be admired for two months. After flowering, capsules containing numerous seeds will mature, so harvest them to prevent the plant from spreading throughout the garden.

Easy to grow, it thrives in ordinary, poor, well-drained, and slightly moist soil. It loves sunny exposures and pairs perfectly in grass gardens with Miscanthus, Stipa, as well as perennials like Asphodines or Gauras.