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Scientific: Eschscholzia californica ssp. mexicana (Synonym: Eschscholzia mexicana)
Common: Mexican poppy (Mexican poppy or Mexican prickly poppy is also the common name of Argemone mexicana), California poppy
Family: Papaveraceae
Origin: Arizona, Southern Utah, to west Texas, south into Sonora, Mexico

Taxonomic clarification: Once thought to be a separate species due to geographic separation, Mexican poppy is now classified as a subspecies cline of Eschscholzia californica, the California poppy (state flower of California). Phenotypic distinctions between Mexican and California poppy are horticulturally insignificant, possibly distinguished only by differences in cotyledons. Reports of differences in flower morphology between California poppy (larger, more orange) and Mexican poppy (smaller, more yellow) are likely due to abiotic factors such as air temperature (desert heat or warmer weather makes California poppy flower size smaller and color more yellow) and available soil moisture.

Pronounciation: Esch-SCHOL-ze-a kal-a-FOR-ni-ka mex-i-CA-na

Hardiness zones:
Sunset 12-24
USDA 9-11 (arid and semi arid regions are best - though try telling that to the Eschscholzia freaks in England)

Landscape Use: Desert wildflower displays in gardens or along roadways or other open desert landscape areas, rock gardens.

Form & Character: Low and small, quite graceful, informal, freely colonizing disturbed areas. Tends to self propagate into a massive display of festive winter/spring color.

Growth Habit: Evergreen, herbaceous winter annual across the Sonoran and Mojave Deserts. Eschscholzia californica is an annual in inland valleys of California or a short-lived perennial in fog prone areas along the California coast. Basally clumping to less than 12-inches tall.

Foliage/Texture: Grayish, glaucous, highly dissected into narrow segments, leaf size varies much with water availbility; fine texture.

Flowers & Fruits: Orange petals, 0.75- to 2.25-inches long that fade to yellow, fruit capsule to 4-inches long, tapers vertically to a point.

Seasonal Color: Flowers in late winter through spring. In Phoenix, flowers from mid-February through March.

Temperature: Mexican poppy grows best when temperatures are between 35o and 85oF. Flower petal color responds to temperature; more orange during cooler weather of winter and more yellow during warmer weather of spring.

Light: Bright, full sun

Soil: Has a wide range of tolerances to different soil textures, but grows best in a light, fast draining soil.

Watering: Give light applications of supplemental water only if winter rains are inconsistent.

Pruning: None, rogue dead or declining plants.

Propagation: Seed, will naturally disperse and colonize Phoenix urban landscapes if plants each spring are left to fruit and age in place (seed will self disperse).

Disease and Pests: Crown rot if soil is chronically wet and poorly drained.

Additional comments: Mexican poppy is an excellent native cool season (winter and spring flowering) annual that should be apart of everyone's winter desert wildflower garden - definitely two thumbs up! Cultivar 'Sun Shades' has a dense array of flowers and grows more prostrate. Other Mexican poppy cultivars with atypical flower colors include 'Champagne & Roses' (champagne pink flower petals) and 'Purple Cap' (reddish purple flower petals). Poppy flowers attract bees.

Biomedical footnote: California or Mexican poppy have been used traditionally as a remedy by native Americans for toothaches (the root cut and the juices applied directly), and as a tea for headaches, anxiety, and insomnia.