The California poppy (Eschscholzia californica) is native to grassy and open areas from sea level to 2,000m (6,500 feet) altitude in the western United States throughout California, extending to Oregon, southern Washington, Nevada, Arizona, New Mexico, and in Mexico in Sonora and northwest Baja California.
It can grow 5–60 cm tall, with alternately branching glaucous blue-green foliage. The leaves are ternately divided into round, lobed segments. The flowers are solitary on long stems, silky-textured, with four petals, each petal 2–6 cm long and broad; their color ranges from yellow to orange, and flowering is from February to September. The petals close at night or in cold, windy weather and open again the following morning, although they may remain closed in cloudy weather. The fruit is a slender dehiscent capsule 3–9 cm long, which splits in two to release the numerous small black or dark brown seeds. It is perennial in mild parts of its native range, and annual in colder climates; growth is best in full sun and sandy, well-drained, poor soil.
It grows well in disturbed areas. In addition to being planted for horticulture, revegetation, and highway beautification, it often colonizes along roadsides and other disturbed areas. It is drought-tolerant, self-seeding, and easy to grow in gardens. It is also pictured in welcome signs while entering California.
It is the official flower of California. April 6 is designated California Poppy Day.

Source: Wikipedia