Oxalis stricta
Oxalis pes-caprae
common yellow oxalis, common yellow wood sorrel, European wood-sorrel, upright yellow oxalis, upright yellow wood-sorrel, yellow woodsorrel
African wood-sorrel, Bermuda buttercup, soursob
1(–3) from base, erect or later leaning or falling over and decumbent, not rooting at nodes, 20–60(–90) cm, herbaceous, villous, hairs ± straight, spreading, usually nonseptate and septate, septate hairs commonly concentrated at nodes, very rarely only nonseptate.
basal and cauline;
stipules rudimentary;
petiole 2–8 cm, hairs septate and nonseptate;
leaflets 3, light green to yellowish green, obcordate, (8–)10–20(–30) mm, lobed 1/5–1/3 length, surfaces glabrous, oxalate deposits absent.
basal, rarely absent at flowering;
petiole 3–12 cm;
leaflets 3, green, rarely mottled with purplish red spots, angular-obcordate, (5–)7–20 mm, lobed 1/4–2/5 length, lobes apically convex, margins and abaxial surface villous, adaxial surface glabrous, oxalate deposits absent.
usually regular cymes, rarely irregular cymes, (1–)5–7(–15)-flowered;
peduncles 3–9(–11) cm.
umbelliform cymes, 2–12(–20)-flowered;
scapes often becoming fistulose proximally, 15–30 cm, sparsely villous to pilose.
homostylous or slightly to strongly heterostylous, usually within or slightly above level of leaves;
sepal apices without tubercles;
petals yellow, without red lines, (6–)8–11 mm.
tristylous in diploids and tetraploids, consistently short-styled in pentaploids;
sepal apices with 2 orange tubercles;
petals deep golden yellow, 15–20 mm.
± cylindric, nearly terete, abruptly tapering to apex, 8–15 mm, villous to puberulent or glabrate, hairs septate.
not seen.
brown, transverse ridges rarely white.
= 18, 24.
= 14, 28, 35.
Oxalis stricta
Oxalis pes-caprae
Oxalis stricta is uncommon and probably adventive in Canada and the western United States. The species is recognized by the combination of its tall (rarely up to nearly a meter), erect stems from a short, simple rhizome; septate hairs; cymose inflorescence; and small flowers. Septate hairs on the stems and petioles are easily recognized (lens) by their colored cross-walls, but they vary greatly in density. In villicaulis forms, the hairs are dense and evenly distributed, but in most plants over the range they are localized around the nodes and intermixed with nonseptate hairs. Often they are sparse; rarely they appear to be absent on plants with greatly reduced vestiture overall.
A. Lourteig (1979) identified this species as Oxalis fontana, typified by a plant from northern China, and applied the name O. stricta to the species identified by G. Eiten (1955, 1963) and here as O. dillenii. The basis for the difference lies in selection of lectotypes. Choice of stricta as the correct epithet acknowledges that the description of O. stricta by Linnaeus best matches these plants and that selection of a Morison illustration as lectotype characterizes the species long-naturalized and weedy in Europe and probably known first-hand by Linnaeus. C. E. Jarvis (2007) has confirmed this choice of lectotype. Oxalis dillenii is appropriately lectotypified by a John Clayton collection from Virginia. The situation has been summarized well by D. B. Ward (2004).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.)
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