Flora of North America species comparison

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Oxalis stricta

Oxalis illinoensis

common yellow oxalis, common yellow wood sorrel, European wood-sorrel, upright yellow oxalis, upright yellow wood-sorrel, yellow woodsorrel

Illinois wood-sorrel
Habit Herbs annual or short-lived perennial, caulescent, rhizomes present, short, stolons absent, bulbs absent. Herbs perennial, caulescent, rhizomes present, with horizontal, white, fusiform tubers or tuberlike thickenings, stolons absent, bulbs absent.
Aerial stems

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.

1(–3) from base, erect, 15–40 cm, herbaceous, glabrate to sparsely to densely villous, hairs ± straight, spreading, septate and nonseptate.
Leaves

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.

cauline;

stipules rudimentary;

petiole 4–7.5 cm, hairs septate and nonseptate;

leaflets 3, green, obcordate, (12–)20–30(–35) mm, lobed 1/5 length, lobes apically truncate, margins green, ciliate, surfaces glabrous, oxalate deposits absent.
Inflorescences

usually regular cymes, rarely irregular cymes, (1–)5–7(–15)-flowered;

peduncles 3–9(–11) cm.

regular or irregular cymes, 1–3(–6)-flowered;

peduncles 3–10 cm.
Flowers

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, mostly at level of leaves;

sepal apices without tubercles;

petals yellow, with prominent red lines proximally, 12–18 mm.
Capsules

± cylindric, nearly terete, abruptly tapering to apex, 8–15 mm, villous to puberulent or glabrate, hairs septate.

oblong-ovoid, 7–10 mm, sparsely puberulent to villous.
Seeds

brown, transverse ridges rarely white.

brown, transverse ridges brown.
2n

= 18, 24.

Oxalis stricta

Oxalis illinoensis
Phenology Flowering (Apr–)Jul–Oct. Flowering Apr–Sep.
Habitat Prairie ravines, riverbanks, sandbars, low woods, mesic forests, floodplains, roadsides, fields, lawns, gardens. Slopes, bluffs, ravines, flood plains, mesic forests, sometimes forming dominant ground cover, commonly on limestone, shale, or calcareous loess.
Elevation 20–1200 m. (100–3900 ft.) 200–500 m. (700–1600 ft.)
Distribution
from FNA
AL; AR; AZ; CO; CT; DC; DE; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NY; OH; OK; PA; RI; SC; SD; TN; VA; VT; WA; WI; WV; WY; BC; MB; NB; NF; NS; ON; PE; QC; SK [Introduced in Europe, Asia, Africa, Pacific Islands (New Zealand), Australia]
[WildflowerSearch map]
[BONAP county map]
from FNA
IL; IN; KY; TN
[BONAP county map]
Discussion

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.)

Differences between Oxalis illinoensis and O. grandis are subtle, but they appear to be correlated with geography. Oxalis illinoensis occupies the western part of the range of O. grandis in the wide sense. The tuberous portions of the rhizomes of O. illinoensis are diagnostic, but they are commonly broken off during collection. M. E. Medley (1993) observed that the two taxa intergrade, and a hybrid population has been identified in Indiana (A. L. Heikens 2003).

Oxalis illinoensis is listed as threatened in Illinois and rare in Indiana.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 12, p. 143. FNA vol. 12, p. 145.
Parent taxa Oxalidaceae > Oxalis Oxalidaceae > Oxalis
Sibling taxa
O. albicans, O. articulata, O. bowiei, O. brasiliensis, O. caerulea, O. californica, O. colorea, O. corniculata, O. debilis, O. decaphylla, O. dichondrifolia, O. dillenii, O. drummondii, O. florida, O. frutescens, O. grandis, O. hirta, O. hispidula, O. illinoensis, O. incarnata, O. intermedia, O. latifolia, O. laxa, O. macrantha, O. metcalfei, O. montana, O. oregana, O. pes-caprae, O. pilosa, O. purpurea, O. suksdorfii, O. texana, O. triangularis, O. trilliifolia, O. violacea
O. albicans, O. articulata, O. bowiei, O. brasiliensis, O. caerulea, O. californica, O. colorea, O. corniculata, O. debilis, O. decaphylla, O. dichondrifolia, O. dillenii, O. drummondii, O. florida, O. frutescens, O. grandis, O. hirta, O. hispidula, O. incarnata, O. intermedia, O. latifolia, O. laxa, O. macrantha, O. metcalfei, O. montana, O. oregana, O. pes-caprae, O. pilosa, O. purpurea, O. stricta, O. suksdorfii, O. texana, O. triangularis, O. trilliifolia, O. violacea
Synonyms O. bushii, O. coloradensis, O. cymosa, O. europaea, O. europaea var. bushii, O. fontana, O. fontana var. bushii, O. interior, O. rufa, O. stricta var. decumbens, O. stricta var. piletocarpa, O. stricta var. rufa, O. stricta var. villicaulis, Xanthoxalis bushii, X. cymosa, X. rufa, X. stricta
Name authority Linnaeus: Sp. Pl. 1: 435. (1753) Schwegman: Phytologia 50: 467. (1982)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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