Garden Oracle / Drought and Heat Tolerant Gardening / Tucson - Phoenix - Arizona - California

Growing Calylophus hartwegii:
Hartweg's Sundrops

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Form: Herb.
Lifespan: Perennial.
Growth rate: Rapid.
Mature Size: 12-18" high and 24" wide.
Flowers: Bright yellow, four wrinkled petals, with a 24 hour lifespan. Each flower opens in the evening, then closes the next afternoon just before the next set of flowers open up, and dries to a pinkish, crumpled wad.
Bloom: Spring and summer.
Fruit: A long, cylindrical seed capsule with four chambers that open lengthwise.
Leaves: Green, linear to thinly lance-shaped.
Stems: Drooping to erect, becoming woody with age, no thorns.
Roots: Taproot.
Wildlife: Attracts butterflies, sphinx moths, bees, and birds. This plant is pollinated by sphinx moths.
Toxic / Danger: No.
Origin: Texas, New Mexico, Arizona and Mexico.

Cultivation and Uses
USDA hardiness zones: 5-9.
Heat tolerant: Yes.
Drought tolerant: Yes.
Sun: Full sun, even with reflected heat, to part afternoon shade. The flowers open earlier in the evening with part afternoon shade.
Water once established: Once or twice a month. This plant tolerates weekly water only in very well drained soil. It does not like high humidity.
Soil: Well drained, dry, pH 6.6-8.5 (neutral to alkaline), saline tolerant.
Mulch: Gravel or bare soil. Avoid organic mulch which keeps the soil too wet.
Prune: In late winter after the last freeze, prune to 1-2" tall and remove dead growth. Hard pruning triggers new growth and blooms.
Litter: Low.
Propagation: Cuttings taken in spring, rootball division, seed sown in the fall and overwintered.
Uses: Ornamental, ground cover.

This plant is a member of the Evening Primrose family (Onagraceae).

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Calylophus hartwegii: Sundrops - flower

Calylophus hartwegii: Sundrops

Latest update: September, 2021
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