Mapping is provisional; there has been confusion with tetragona or brevistipata and some records remain dubious. O. perennis is a largely northeastern species of varied open habitats on seasonally damp acid soils, concentrated in the Great Lakes area, central Appalachians, New England and adjacent Canada (K). Some disjunct records to the south and west need revision, but the extensions into se. Ind. (D), se. Ohio and the southern Appalachians (W) are verified. O. perennis appears close to the largely more southern tetragona-fruticosa complex, but it differs as follows (Munz 1937, Straley 1977; F, Y, W): overwintering basal rosettes (on shallow stolons) relatively well-developed and often persistent into early growing season (but with leaves only 2-4 cm long versus 3-12 cm); inflorescence stipitate-glandular when fresh (versus glandular or pubescent), often nodding or secund (versus rarely so, relatively elongated); flowers generally smaller, with sepals 2-4 x 0.5-1 mm (versus 5-20 x 2-3 mm), petals mostly 5-10 x 4-10 mm long (versus 15-25 x 10-20 mm); capsules ca. 5-10 x 2-3 mm (versus 5-20 x 2-6 mm), more or less clavate (versus clavate or oblong), tapering to stipe 1-4 mm long (versus tapering or abruptly contracted to stipe 1-10 mm); seeds mostly 0.6-0.8 x 0.2-0.3 mm (versus 0.8-1.0 x 0.3-0.5 mm). The species is reportedly just diploid (2n = 14), but a "complex heterozygote" with potential for much self-pollination: "stigma and anthers held at the same level at anthesis [versus above], the anthers shedding pollen directly on the stigma" (Straley 1977; Cr). Compared to the tetragona-fruticosa complex, perennis is much less common in Ky. A few colls. mapped here should perhaps be transferred to tetragona, including those from Appalachian riverbanks or nearby; see notes under tetragona. Plants in western regions of Ky. and Tenn. that have been called perennis by JC and MM (especially in MARS), now appear closer to brevistipata; see notes under O. tetragona var. sharpii.