The California poppy (Eschscholzia californica) is a perennial and annual plant, native to the United States, and the official state flower of 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.
Full-size version and further info: http://commons.wikimedia.org/wiki/File:Eschscholzia_californica_(Shallow_DOF).jpg