Groundcover
Mexican Evening Primrose
Oenothera speciosa · Onagraceae
Also called: Pink Evening Primrose, Showy Evening Primrose, Mexican Primrose, Pink Ladies
Mexican Evening Primrose (Oenothera speciosa) is a low-water groundcover well suited to Tucson and the low desert. It thrives in full sun to partial shade, with a fast growth rate.
Mexican Evening Primrose at a glance
- Water use
- Low (established)
- Sun
- Full sun to partial shade; afternoon shade reduces summer heat stress.
- Mature size
- 10-18 in H x spreading 2-4 ft+ (spreads indefinitely by rhizomes)
- Growth rate
- Fast
- Bloom
- Pink (pale pink with yellow centers; fades lighter), Spring (March-May), with a peak flush; may rebloom lightly in fall.
- Cold hardiness
- Cold hardy to about 0-10 F (USDA zones 5-11); dies back in winter and regrows.
- Soil
- Adapts to most well-drained soils including poor, sandy, and rocky soils; spreads most aggressively in richer, moister soil.
- Native range
- Native to the south-central United States and Mexico (including parts of Texas and northern Mexico); naturalized widely. Not considered native to the Sonoran Desert of Arizona.
- Best used as
- Groundcover for large informal areas, Slope cover and erosion control, Naturalized/wildflower areas, Filler in low-water beds
- Wildlife
- Flowers attract bees, butterflies, hawk moths, and other pollinators.
- Toxicity
- Not known to be significantly toxic to people or pets.
How to grow Mexican Evening Primrose in Tucson & the low desert
Watering
Drought tolerant once established; in Tucson water every 1-2 weeks in spring for best bloom and reduce in summer. Excess water and fertility make it spread invasively.
Fertilizer & nutrients
None needed; rich soil and fertilizer encourage aggressive, invasive spread. Withhold feeding to keep it in check.
Pruning & care
Mow or shear back hard after the spring bloom to control rangy growth and reseeding; cut to the ground when it goes dormant or looks ragged. Control its rhizomatous spread by edging or removal.
Notes
A fast-spreading, rhizomatous perennial groundcover prized for its showy pink spring flowers but notorious for aggressive, sometimes invasive spread in irrigated Tucson landscapes. Best confined to areas where its spread is acceptable or contained by hardscape. Goes summer/winter dormant.
Sources: University of Arizona Cooperative Extension; AMWUA Landscape Plants for the Arizona Desert; Arizona-Sonora Desert Museum; Tohono Chul / Tucson Botanical Gardens references