Trillium chloropetalum
Trillium chloropetalum, also known as giant trillium, giant wakerobin, or common trillium, is a species of flowering plant in the family Melanthiaceae. It is endemic to the western U.S. state of California, being especially frequent in and around the San Francisco Bay Area. Description. "Trillium chloropetalum" is a perennial, clump-forming herbaceous plant with a thick underground rhizome. Like all trilliums, it has a whorl of three bracts (leaves) and a single trimerous flower with 3 sepals, 3 petals, two whorls of 3 stamens each, and 3 carpels fused into a single ovary with 3 stigmas. Since its  flower has no stalk, "T. chloropetalum" belongs to subgenus "Sessilium", the sessile-flowered trilliums. It is one of the largest of all "Trillium" species, with a scape (stem) from long. The bracts are broadly ovate, long and wide, usually with brownish mottling but sometimes unmottled. Petal color is highly variable, typically ranging from pale greenish yellow to greenish bronze (or purplish green) to dark purple. A variety that lacks yellow pigments has petal colors ranging from white to reddish-purple. The flower petals enclose purple stamens, long, and a purple ovary. Flowering occurs from late February to early April. In  the San Francisco Bay Area, a white-petaled form of "T. chloropetalum" is often confused with "T. albidum", which also has white petals. The former is distinguished by the purple pigment in its anther connective tissue, a character lacking in "T. albidum". Taxonomy. In 1856, John Torrey described "Trillium sessile" var. "chloropetalum" based on a specimen collected by John Milton Bigelow two years earlier in the "redwoods" of California. At the time, Bigelow was exploring the valleys and tributaries of the Sacramento and San Joaquin rivers, but the precise original location of his specimen remains unknown. In 1903, Thomas Jefferson  Howell described the species "Trillium chloropetalum" based on Torrey's variety. The epithet "chloropetalum" means "green-petaled". In 1975, John Daniel Freeman published an influential revision of subgenus "Sessilium" that included the description of a new species "Trillium albidum" and a completely new circumscription of "Trillium chloropetalum" . By separating out white-flowered "T. albidum", Freeman was able to provide a rational circumscription of "T. chloropetalum" that includes the following taxa: The petals of "T. chloropetalum" var. "chloropetalum" always show yellow pigments but these are often masked by purple or other pigments. In contrast, the petals of "T. chloropetalum" var. "giganteum  lack yellow pigments altogether. The former is characterized by the green-petaled form described by Torrey while the latter includes a white-flowered form of T. chloropetalum" distinguished from "T. albidum" by the presence of dark purple stamens and carpels. Freeman's treatment of "Trillium chloropetalum" is widely (if not universally) accepted. Some authorities consider "Trillium chloropetalum" var. "giganteum" to be a synonym for "Trillium chloropetalum", but even those authorities cite Freeman. Distribution and habitat. "Trillium chloropetalum" is endemic to California. Some authorities claim the species ranges across ten California counties, from Monterey County on the central California coast to  Lake County in the north central part of the state: Other authorities claim that "T. chloropetalum" has a broader range that extends northward to Siskiyou County or southward to Santa Barbara County. "T. chloropetalum" is found at the edges of redwood forests and chaparral, usually on moist slopes, canyon banks, and alluvial soils. Uses. The variety "Trillium chloropetalum" var. "giganteum", with its deep maroon flower petals, gained the Award of Garden Merit (AGM) from the Royal Horticultural Society in 1993.