Oenothera heterophylla, commonly known as Largeflower Eveningprimrose, Variable-leaf Evening-primrose, or Nightwillow Sun Cup, is a perennial herb native to a variety of habitats including prairies, grasslands, open woodlands, and desert scrub in the Southwestern United States. It typically grows at a moderate rate to a height of 1-3 feet (0.3-0.9 meters) and a width of 1-2 feet (0.3-0.6 meters). This plant features lanceolate leaves and its stems are often reddish. The large, showy yellow flowers open in the evening and close by the next noon, blooming profusely in the summer. The flowers are highly attractive to pollinators such as moths and bees.

The Largeflower Eveningprimrose is valued for its ornamental flowers and its ability to adapt to dry conditions, making it suitable for xeriscaping. It is used in native plant gardens, rock gardens, and borders. It thrives in full sun and prefers medium or fast-draining sandy or loamy soils. While it requires medium amounts of water, it is drought-tolerant once established. Gardeners should be aware that it can self-seed and spread, potentially becoming weedy in ideal conditions.CC BY-SA 4.0