Kingdom Plantae Family Crassulaceae | Order Saxifragales Genus Rhodiola
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Rhodiola is a genus of perennial plants in the family Crassulaceae that resemble Sedum and other members of the family. Like sedums, Rhodiola species are often called stonecrops. Some authors merge Rhodiola into Sedum.
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Rhodiola species grow in high-altitude and other cold regions of the Northern Hemisphere. Den virtuella floran gives the number of species as 36, the Angiosperm Phylogeny Group gives it as 60, and the Flora of China gives it as about 90, with 55 in China and 16 endemic there. Flora of North America lists only three species in the United States and Canada.
Among the distinguishing characters of the genus are two series of stamens totaling twice the number of petals; free or nearly free petals (not joined in a tube); a stout rhizome from whose axils the flowering stems rise; and a basal rosette of leaves. This genus contains the only species of Crassulaceae that have unisexual flowers.
The Holarctic species Rhodiola rosea is used in herbal medicine. A number of species are grown as ornamentals, but growing them is difficult outside their native subarctic and alpine climates.
The name combines the Greek rhodon, meaning rose and referring to the rose-like smell of the roots, with the Latin diminutive suffix -iola.
Chemical composition
Rhodionin is a herbacetin rhamnoside found in Rhodiola species.
Ecology
Dioecy, having separate male and female flowers, has evolved at least three times in the genus, and reversals to a hermaphrodite condition have also occurred, which is a rare occurrence in flowering plants. It has been suggested that dioecy in the genus may correlate with abiotic pollination in the cold environment.
Species list
Species include: