Contributed by John C. Kees & Alan S. Weakley
A genus of about 145 or more species (188 or more taxa), herbs, of America (especially temperate regions). This treatment provisional, with further revision likely, especially in the O. fruticosa complex.
ID notes:The key requires flowering or fruiting material. Mature fruits can usually be found lower down on the inflorescence axis in flowering material. Frequent reference is made to different types of pubescence on plant surfaces; a hand lens is helpful. Some definitions – strigillose: covered in short, straight, stiffly incurved or appressed hairs; hirtellous: covered in short, soft, spreading hairs; glandular-puberulent: covered in tiny stalked glands (will be sticky to the touch); hirsute: covered in long, stiff hairs; villous: covered in long, flexible, sometimes shaggy hairs; pilose: covered in soft, straight, long hairs. The presence or absence of hairs with pustular (swollen, blister-like) bases is sometimes used to distinguish closely related species. Free sepal tips refer to the horn-like tips of the sepals that project at the apex of flower buds.
Ref: Dietrich & Wagner (1988); Dietrich, Wagner, & Raven (1997); Munz (1938); Munz (1965); Sorrie, LeBlond, & Weakley (2018b) In Weakley et al. (2018b); Straley (1977); Towner & Raven (1970); Wagner (2014); Wagner (2021) In Flora of North America Editorial Committee (2021); Wagner, Hoch, & Raven (2007); Wagner, Hoch, & Zarucchi (2015); Wagner, Krakos, & Hoch (2013). Show full citations.