Oenothera glazioviana aka Large Flowered Evening Primrose

Oenothera glazioviana is a biennial in the evening primrose family, Onagraceae. Its common names include large-flowered evening primrose and redsepal evening primrose. Kew records it as a cultivated plant that arose in Europe. Its parents are Oenothera elata and Oenothera grandiflora. It has no known wild habitat, according to Plants For A Future. It is not native to Britain or Ireland.

This upright plant reaches 3.3–4.9 feet [1–1.5 metres] in gardens. Its spread is about 0.3–1.6 feet [0.1–0.5 metres]. It forms a low rosette of oval leaves. The leaves have a crinkled surface, and the foliage is deciduous. Flowers appear in the second year, in summer and autumn. Clusters grow at the tops of the stems. Red buds open in the evening to reveal pale yellow flowers. Each flower has a bowl shape. The plant reaches its full size within one to two years.

Give it full sun and soil that drains well. The RHS recommends poor to moderately fertile ground. Sandy soil and loam both suit it. It accepts acid, neutral, and alkaline soil, with dry to moist conditions. Choose an open site with shelter. A south-facing or west-facing position suits its need for sun. The RHS rates its hardiness as H5. This covers winter lows of 5–14°F [-15 to -10°C]. Plants For A Future lists USDA zones 3–7.

Use it in flower beds, borders, or informal cottage gardens. The RHS also lists coastal gardens, gravel gardens, and wildflower meadows. Its upright form and evening flowers give these plantings seasonal interest. Plants For A Future lists it as scented and wildlife-attracting. Sow seed in early summer to raise new plants. Cut the stems back once flowering ends. Pests rarely cause trouble, according to the RHS. Powdery mildew and leaf spot can still affect it.

Plants For A Future lists roots, shoots, leaves, and oil as edible. Cooked roots can serve as a vegetable, much like salsify. Young shoots can be eaten raw or cooked. The seeds yield an edible oil, but hand harvesting is difficult. The source also records medicinal uses for this oil. These reports do not establish safe or effective treatments. It lists no known hazards, rather than confirming safety for every use.