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 through yellow, orange and red, with flowering from February to September in the northern hemisphere (spring, summer, autumn).
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 numerous small black or dark brown seeds.
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.
The California poppy has been used as an herbal treatment for tooth pain. The odontalgic properties are found in the plant´s root, which is cut and applied directly to the affected area.
As a tincture, it is used for its antimicrobial properties applied externally to cuts and scrapes. The herb´s analgesic and antispasmodic properties have been found useful in the relief of acute nerve and muscular centered pain.
It has been used as a remedy in cases of high fever, rapid pulse, and persistent spasmodic cough. A tincture made from the root of the California poppy is prepared as an external wash for suppressing lactation (the production of milk) in breastfeeding women.