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Eschscholzia californica (California poppy, golden poppy, California sunlight, cup of gold) is a species of flowering plant in the family Papaveraceae, native to the United States and Mexico, and the official state flower of California.
It is a perennial or annual growing to 5–60 in (13–152 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 to 6 cm (0.79 to 2.36 in) long and broad; flower color ranges from yellow to orange, with flowering 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 to 9 cm (1.2 to 3.5 in) long, which splits in two to release the numerous small black or dark brown seeds. It survives mild winters in its native range, dying completely in colder climates.
Its native habitat includes California, extending to Oregon, Washington, Nevada, Arizona, New Mexico, Sonora and northwest Baja California.
The Antelope Valley California Poppy Reserve is located in northern Los Angeles County, California. At the peak of the blooming season, orange petals seem to cover all 1,745 acres (706 ha) of the reserve. Other prominent locations of California poppy meadows are in Bear Valley (California, Colusa County), Point Buchon and numerous other locations.
The species is highly variable, with over 90 synonyms. Some botanists accept two subspecies — one with four varieties (e.g., Leger and Rice, 2003) — though others do not recognize them as distinct (e.g., Jepson 1993):
- E. californica subsp. californica, native to California, Baja California, and Oregon, widely planted as an ornamental, and an invasive elsewhere (see below).
- E. californica subsp. californica var. californica, which is found along the coast from the San Francisco Peninsula north. They are perennial and somewhat prostrate, with yellow flowers.
- E. californica subsp. californica var. maritima (E. L. Greene) Jeps., which is found along the coast from Monterey south to San Miguel Island. They are perennial, long-lived, glaucous, short in stature, and have extremely prostrate growth and yellow flowers.
- E. californica subsp. californica var. crocea (Benth.) Jeps., which grows in non-arid inland regions. They are perennial, taller, and have orange flowers.
- E. California subsp. californica var. peninsularis (E. L. Greene) Munz, which is an annual or facultative annual growing in arid inland environments.
- E. californica subsp. mexicana (E. L. Greene) C. Clark, the Mexican Gold Poppy, which is found in the Sonoran Desert. Some authorities refer to it as E. Mexicana. 
Eschscholzia californica was the first named member of the genus Eschscholzia, named by the German botanist Adelbert von Chamisso after the Baltic German botanist Johann Friedrich von Eschscholtz, his friend and colleague on Otto von Kotzebue’s scientific expedition to California and the greater Pacific in mid-1810s aboard the Russian ship Rurik.
E. californica is drought-tolerant, self-seeding, and easy to grow in gardens. It is best grown as an annual, in full sun and sandy, well-drained, poor soil. Horticulturalists have produced numerous cultivars with a range of colors and blossom and stem forms. These typically do not breed true on reseeding. Seeds are often sold as mixtures. The following cultivars have gained the Royal Horticultural Society's Award of Garden Merit:-
- E. californica
- 'Appleblossom Bush' (pink)
- 'Dali' (red)
- 'Lemon Bush' (pale yellow)
- 'Rose Chiffon' (pink and white)
- Thai Silk Series (mixed colours)
An aqueous extract of the plant has sedative and anxiolytic action. The extract acts as a mild sedative when smoked. The effect is far milder than that of opium. California poppy contains a different class of alkaloids:
"An aqueous alcohol extract of Eschscholzia californica has been evaluated for benzodiazepine, neuroleptic, antidepressant, antihistaminic and analgesic properties. The plant extract did not protect mice against the convulsant effects of pentylenetetrazol, and did not cause muscle relaxant effects, but appeared to possess an affinity for the benzodiazepine receptor. The extract induced peripheral analgesic effects in mice but did not possess antidepressant, neuroleptic or antihistaminic effects."
Because of its beauty and ease of growing, the California poppy was introduced into several regions with similar Mediterranean climates. It is commercially sold and widely naturalized in Australia, and was introduced to South Africa, Chile, and Argentina. It is recognized as a potentially invasive species within the United States, although no indications of ill effects have been reported for this plant where it has been introduced outside of California. Ironically, it has been displaced in large areas of its original habitat, such as Southern California, by more invasive exotic species, such as mustard or annual grasses.
In Chile, it was introduced from multiple sources between the mid-19th century and the early 20th century. It appears to have been both intentionally imported as an ornamental garden plant, and accidentally introduced along with alfalfa seed grown in California. Since Chile and California have similar climatic regions and have experienced much agricultural exchange, it is perhaps not surprising that it was introduced to Chile. Once there, its perennial forms spread primarily in human-disturbed environments (Leger and Rice, 2003).
Interestingly, the introduced Chilean populations of California poppy appear to be larger and more fecund in their introduced range than in their native range (Leger and Rice, 2003). Introduced populations have been noted to be larger and more reproductively successful than native ones (Elton, 1958), and there has been much speculation as to why. Increase in resource availability, decreased competition, and release from enemy pressure have all been proposed as explanations.
One hypothesis is that the resources devoted in the native range to a defense strategy, can in the absence of enemies be devoted to increased growth and reproduction (the EICA Hypothesis, Blossey & Nötzold, 1995). However, this is not the case with introduced populations of E. californica in Chile: the Chilean populations were actually more resistant to Californian caterpillars than the native populations (Leger and Forister, 2005).
As the official state flower of California Eschscholzia californica is pictured on welcome signs along highways entering California. It was selected as the state flower by the California State Floral Society in December 1890, winning out over the Mariposa lily (genus Calochortus) and the Matilija poppy (Romneya coulteri) by a landslide, but the state legislature did not make the selection official until 1903. Its golden blooms were deemed a fitting symbol for the Golden State. April 6 is designated California Poppy Day.
- Californidine, a chemical compound found in Eschscholzia californica
- "California poppy, golden poppy, copa de oro". Florida Museum of Natural History, University of Florida. Retrieved April 9, 2012.
- Eschscholzia mexicana at Arizona State University
- RHS Plant Selector Eschscholzia californica AGM / RHS Gardening
- RHS Plant Selector Eschscholzia californica 'Appleblossom Bush' (Thai Silk Series) AGM / RHS Gardening
- RHS Plant Selector Eschscholzia californica 'Dali' AGM / RHS Gardening
- RHS Plant Selector Eschscholzia californica 'Lemon Bush' (Thai Silk Series) AGM / RHS Gardening
- RHS Plant Selector Eschscholzia californica 'Rose Chiffon' (Thai Silk Series) AGM / RHS Gardening
- RHS Plant Selector Eschscholzia californica Thai Silk Series AGM / RHS Gardening
- Rolland, A.; Fleurentin, J.; Lanhers, M.C.; Younos, C.; Misslin, R.; Mortier, F.; Mortier, J.M. (June 1991). "Behavioural Effects of the American Traditional Plant Eschscholzia Californica: Sedative and Anxiolytic Properties". Planta Medica 57 (3): 212–216. doi:10.1055/s-2006-960076.
- Klvana, M.; Chen, J.; Lepine, F.; Legros, R.; Jolicoeur, M. (July 2006). "Analysis of Secondary Metabolites From Eschscholtzia Californica by High-performance Liquid Chromatography". Phytochemical Analysis 17 (4): 236–242. doi:10.1002/pca.913.
- MacLeod, B.P.; Facchini, P.J. (2006). "Methods for Regeneration and Transformation in Eschscholzia Californica: A Model Plant to Investigate Alkaloid Biosynthesis". Methods in Molecular Biology 318: 357–368. doi:10.1385/1-59259-959-1:357.
- Rolland, A.; Fleurentin, J.; Lanhers, M.C.; Misslin, R.; Mortier, F. (August 2001). "Neurophysiological Effects of an Extract of Eschscholzia Californica Cham. (Papaveraceae)". Phytotherapy Research 15 (5): 377–381. doi:10.1002/ptr.884.
- "California Government Code §421". State of California. Retrieved April 14, 2012.
- Blossey, B., and R. Nötzold. 1995. Evolution of increased competitive ability in invasive non-indigenous plants: a hypothesis. Ecology 83: 887-889.
- Elton, C. S. The ecology of invasions by animals and plants. Chapman & Hall, London.
- Leger, E. A. and K. J. Rice. 2003. Invasive California poppies (Eschscholzia californica Cham.) grow larger than native individuals under reduced competition. Ecology Letters 6:257-264.
- Leger, E. A., and M. L. Forister. 2005. Increased to generalist herbivores in invasive populations of the California poppy (Eschscholzia californica). Diversity and Distributions 11: 311-317.
- Jepson Flora Project (1993): Eschscholzia californica
- Jepson eFlora (2012) Treatment
- The California poppy and its relatives
- Folia: List of California Poppy Cultivars
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