This is a widespread (cosmpolitan) perennial. Its native origins and historical spread remain somewhat obscure (Cr; W; Lovett-Doust et al. 1985, Nesom 2009), perhaps bound up with early human history. There has been much confusion with florida (perhaps its closest relative), with dillenii and with corniculata (in earlier versions of Gray's Manual; F). The earliest definite records from Ky. are colls. of C.W. Short made during 1830-60 (GH etc.).. Under "corniculata" Gm (1914) noted: "A common weed of no great consequence, found about dwellingd, along roadsides, in pastures and cultivated ground thruout the summer months... It reaches finally a height of about a foot and then bears numerous elongate five-sided pointed pods, three or more on a stem... [unlike] O. stricts [meaning dillenii], a much smaller plant... Introduced with forage seeds from Europe." Compared to dillenii, stricta tends to have larger cymes (usually with 5-7 flowers versus 1-5), the pedicels erect to ascending (versus deflexed to horizontal) and more frequent bracteoles. Seeds are brown or "very rarely with light lines on the transverse ridges" (Lovett-Doust et al. 1985). O, stricta can also be diagnosed by the presence of relatively long spreading septate hairs on stems, petioles (leaves?) and capsules, at least on petioles or concentrated near nodes (as well as spreading non-septate hairs). In contrast, dillenii has stems (at least above) with dense antrorsely appressed non-septate hairs. O. stricta also differs in its obsolescent stipules (versus usually present) and lack of taproot, but often with "autumnal fleshy subterranean stolons" (F) or with "short herbaceous to lignescent rhizomes" (W) instead (versus usually just decumbent to slightly "stoloniform" or perhaps rhizomatous above a taproot). O. stricta is often a relatively tall weed in sunny habitats (up to 60 cm versus 40 cm); dillenii is also weedy but tends to be more shade-tolerant and more decumbent, especially where mowed. Although both species are potentially perennial, they often appear largely annual; descriptions of stolons or rhizomes have been somewhat inconsistent between treatments, and it is likely that much environmental and genetic variation exists in the degree or means of perenniation.