Calylophus hartwegii: Hartweg’s Sundrops / Fendler’s Sundrops
Growth rate: Rapid.
Mature Size: 12-18″ high and 24″ wide.
Flowers: Bright yellow, four petals, 24
hour lifespan, open in the evening and close the next afternoon just before the next
set of flowers open.
Bloom: Spring and summer.
Fruit: Cylindrical seed capsule.
Leaves: Green, linear to thinly
Stems: No thorns. Drooping to erect and become woody.
Roots: Spreads by rhizomes.
Wildlife: Attracts butterflies, bees, birds.
Toxic / Danger: No.
Origin: Texas, New Mexico, Arizona
Cultivation and Uses
USDA hardiness zones: 5-9.
Heat tolerant: Yes.
Drought tolerant: Yes.
Sun: Full sun to part shade.
Water once established: Once or twice a month. Tolerates weekly water in very well drained soil.
Soil: Well drained, dry, pH 6.6-8.5 (neutral to alkaline).
Prune: Shear in late winter. Deadheading promotes more flowers.
Propagation: Seed, cuttings, root division.
Uses: Ornamental, ground cover.
Comments: This is a member of Onagraceae, the Willowherb or Evening Primrose family.