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 Sessilia 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: •
Trillium chloropetalum var.
chloropetalum •
Trillium chloropetalum var.
giganteum 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==