Flora of North America species comparison

Outside its native range, Oxalis pes-caprae is mostly represented by a sterile pentaploid morph, although tetraploids also are known. The occurrence of both pentaploid and tetraploid individuals in the exotic range may be the result of independent introductions (P. Michael 1964; R. Ornduff 1986). Fruit production has not been observed in North America, and the plants are assumed to be seed-sterile (Ornduff 1987). Bulbs of O. pes-caprae are rarely collected, as they detach easily from the vertical, rootlike stems. Each bulb may produce over 20, small, whitish bulblets each year. Bulblets may also be formed at the soil surface crown.

Oxalis pes-caprae was reported by J. K. Small (1933) to occur in waste places and cultivated grounds in northern Florida, but as noted by D. B. Ward (2004), no Florida specimens are known.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Oxalis montana of eastern North America and O. oregana of the Pacific region have sometimes been treated as disjunct geographical taxa of the European (or Eurasian, depending on taxonomic interpretation) O. acetosella Linnaeus. The three are very similar and surely are closely related. Section Acetosellae Reiche also includes the Asian O. griffithii Edgeworth & Hooker f., O. leucolepsis Diels, and O. obtriangulata Maximowicz, as well as O. magellanica G. Forster (South America, New Zealand, Tasmania); the first two of these also have been treated as taxa within O. acetosella (see synonyms in Liu Q. R. and M. F. Watson 2008). Among all these, typical O. acetosella, the two American taxa, and O. magellanica have erect flowers, while those of the strictly Asian taxa are distinctly nodding, perhaps suggesting that the latter are monophyletic.

Oxalis oregana stands apart from O. montana and typical O. acetosella in its larger leaves and flowers and its strigose-villous (versus glabrous) sepals. Each of the three is distinct in petal coloration and this difference between O. acetosella and O. montana is perhaps the only one between them besides the geographical disjunction. In O. montana, the orange-yellow region near the petal base is constricted to a spot (versus a lateral band in typical O. acetosella) and a light and diffuse but distinct rose colored band lies immediately distal to the spot, connecting among the petals to form a circle. Oxalis acetosella in the strict sense occurs from Iceland to southern Europe (and possibly northern Africa), reportedly stretching as a broad band completely across Eurasia to Japan to Korea (J. F. Veldkamp 1971; Liu Q. R. and M. F. Watson 2008). Attributions of O. acetosella to Pakistan and other Himalayan localities apparently are based on plants of O. griffithii.

(Discussion copyrighted by Flora of North America; reprinted with permission.)