Oenothera macrocarpa aka Missouri Evening Primrose

Oenothera macrocarpa is a low plant that spreads and lives for years. It has soft growth, not woody stems. Its other names are Missouri primrose and Ozark sundrops. It belongs to Onagraceae, the evening primrose family. It grows wild in the central and east-central United States. Its range extends south into Coahuila, Mexico. This plant comes from temperate lands and sheds its leaves. It does not stay green all year.

Leafy stems creep and trail across the ground. The RHS gives a height of about 0.5 feet [0.15 metres]. Chicago Botanic Garden reports 1 foot [0.30 metres]. The RHS also lists a wider height range. This reaches 1.6 feet [0.5 metres]. Its listed spread reaches 1.6 feet [0.5 metres] too. Trailing stems can reach 1 foot [0.30 metres] long. Red stems bear narrow, oblong leaves with clear, silvery midribs. These ribs run down the middle of each leaf. Plants reach full size in two to five years.

Large yellow flowers stand out above the low leaves. Each bloom grows alone, spanning about 0.33–0.42 feet [0.10–0.13 metres]. Missouri Botanical Garden notes their scent and showy look. It gives a bloom season of May through August. The RHS lists late spring through early autumn instead. Chicago also gives May through August as the bloom season. The fruit adds interest once the blooms fade.

Grow it in full sun, in soil that drains well. Poor soil suits it, as does soil with a moderate level of nutrients. It also grows on stony sites. The RHS lists chalk, loam, and sand as suitable soils. It accepts acidic, neutral, and alkaline soil. Missouri Botanical Garden also lists clay and shallow, rocky soil. It suits dry to moderately moist sites and withstands drought. Keep excess winter rain from leaving its roots wet. The RHS gives it a UK hardiness rating of H5. Missouri Botanical Garden lists USDA zones 3–7. Chicago lists zones 4–7.

Its low growth suits border edges, rock gardens, and gravel beds. It also fits cottage gardens, meadows, and native plant gardens. The RHS lists pots, banks, and slopes as uses too. It needs little care and no pruning. Sow seed in pots in a cold frame in early spring. Missouri Botanical Garden reports few serious pest or disease problems. The RHS warns that slugs may still cause harm. Leaf spots, mildews, and root rot can also occur. Wet soil that drains poorly raises the risk of root rot.