- Name also: Californian Poppy, Golden Poppy, California Sunlight, Cup Of Gold
- Family: Poppy Family – Papaveraceae
- Growing form: Annual, sometimes perennial herb.
- Height: 30–50 cm (12–20 in.). Stem erect–ascending, abundantly branching, glabrous blueish green, not containing latex.
- Flower: Regular (actinomorphic), 3–4 cm (1.2–1.6 in.) wide. Petals 4, uniformly coloured orange-yellow or yellow, or with orange-yellow base. White, orange and red-flowered species have also been bred. Sepals (2) fused forming a sharp-tipped hood, dropping when flower opens. Stem under flower with ring-like remains of calyx. Stamens many, yellow–orange, anthers longer than filaments. Gynoecium composed of many fused carpels. Flowers solitary, terminating long scape.
- Leaves: Alternate, long-stalked, biternate, lobes narrow, linear, thin, blueish green.
- Fruit: Narrow, 5–10 cm (2–4 in.) long, glabrous, clearly rutted capsule. (Unripe with sharp-tipped, glossy cone.)
- Habitat: Roadsides, landfill and wasteland. Ornamental, sometimes an escape from yards.
- Flowering time: July–September.
California poppy is a feral plant in North America, especially in the south-west, and it is the official flower of California (California Poppy Day is officially celebrated on the 6th of April). California poppy’s picture even features on the “Welcome to California” sign at the state line. In Finland the plant is grown as an ornamental, but it escapes to a certain extent into the wild, although it doesn’t form permanent stands there. In some countries, e.g. Australia, California poppy is classed as a nuisance established alien. California poppy has been bred to produce different varieties, whose flowers range in colour from white to red.
Other yellow-flowered poppies or their close relatives in Finland include at least Iceland poppy (Papaver croceum), yellow-horned poppy and Welsh poppy. The species are pretty easy to tell apart. Welsh poppy’s leaves with quite large lobes are alternate on stem (no rosette) and flowers are long-stalked. Iceland poppy’s leaves form a rosette and its stem is leafless. Yellow-horned poppy’s blue-green leaves are located in rosette and along stem amplexicaul, flowers are short-stalked.
Yellow-horned Poppy (Yellowhorn Poppy)
The leaves of yellow-horned poppy are pinnately lobed and greyish as the genus name glaucium tells us (Greece glaucos means bluish grey – greenish grey). Rosette leaves are stalked, stem leaves amplexicaul. Flower is short-stalked and capsule longer than that of California poppy.