18a. Trillium chloropetalum var. chloropetalum
Petals yellow, yellowish green, greenish purple, to deep purple, bronze-green or brown, never white, yellow pigment always present even when masked by purple.
Flowering late winter--spring (late Feb--early or mid Apr). Variable habitat: edges, openings in and along ravines in redwood forest, thickets and tangles of cut-over forest, stream flats in deciduous woods, chaparral brushland, open wooded sloped on dunes, brushy islands in surprisingly open grasslands, but usually where soil remains moist most of the season; 0--2000 m; Calif.
Trillium chloropetalum var. chloropetalum is found in San Mateo and Santa Clara counties and in the counties along the east side of San Francisco Bay, north to Napa and Lake counties in California. It is more frequent east and south of the San Francisco Bay region.
J. D. Freeman (1975) determined chemically that all plants of var. chloropetalum have yellow pigment present in petals, though it may be masked by purple. My own quite limited field observations seem to indicate that plants of this variety are somewhat shorter at flowering than those of var. giganteum, and that the bracts of var. chloropetalum show a slightly metallic luster at that stage of development.