Romneya coulteri

Subshrub perennial with a perennial base and semi-woody stems, from the Papaveraceae family, native to southern California and northern Baja California (Mexico). It naturally grows in dry scrublands, sunny canyons, embankments, and disturbed grounds with sandy or gravelly soil, in arid to semi-arid conditions.

It forms large bushy masses, vigorously suckering, reaching 2 to 2.5 meters in height under favorable conditions, and spreading very widely. The stems are erect, glaucous, bearing deeply pinnatifid foliage, with a very characteristic bluish-gray green.

The flowers are spectacular, among the largest of the genus: up to 12 to 15 cm in diameter, with six slightly crumpled satin white petals, surrounding a dense cluster of bright yellow stamens. The flower buds are globular, covered with well-visible bristly hairs. In its natural habitat, blooming extends from May to July. In cultivation under temperate climates, it generally blooms from June to August.

It requires full sun, very well-drained soil, poor to moderately fertile, and sufficient summer heat. Its suckering root system can become invasive; any disturbance of the roots stimulates the production of new shoots.