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Herbs annual or short-lived perennial, caulescent, rhizomes present, <short>, 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>. 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. Inflorescences usually regular cymes, rarely irregular cymes, (1–)5–7(–15)-flowered; peduncles 3–9(–11) 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. Capsules ± cylindric, nearly terete, abruptly tapering to apex, 8–15 mm, villous to puberulent or glabrate, <hairs septate>. <Seeds brown, transverse ridges rarely white>. 2n = 18, 24.
Erect or ascending, sts scrambling herb up to 2-(3) dm. tall, from a stout to slender sts multicipital stock merging into a long taproot. Lower branches wiry decumbent then ascending; upper ± spreading, glab. to pilose. Lvs trifoliolate, on slender glab. to pilose petioles up to 2 cm. or more long; stipules 0 or occ. present and minute. Lflts rather pale green, obovate, emarginate, cuneately narrowed to base, 8-10-(20) mm. diam., us. glabrate, margins sts ciliate, sinus us. rather broad. Peduncles up to ± 15 cm. long, (1)-5-(8)-fld; pedicels up to ± 1 cm. long; bracteoles linear-lanceolate, minute. Fls ± 5 mm. diam.; sepals narrow-ovate, subacute, ± 6 mm. long; petals yellow, obovate to cuneiform, ± 8 mm. long. Capsule 10-15 mm. long, cylindric, clad in long hairs or glabrate; styles persistent. Seeds several to many, brown, glossy.
Perennial from long slender rhizomes, prostrate to more often erect and to 5 dm; stems pubescent with spreading, blunt-tipped, septate hairs, sometimes also strigose, seldom glabrous; stipules none; lfls 1–2 cm wide, usually glabrous to merely ciliate; peduncles usually exceeding the fls, 2–7-fld; pet 4–9 mm, yellow; fr 8–15 mm, provided with spreading, flexuous, septate hairs; 2n=18–24. Nearly cosmopolitan weed, often in natural habitats as well, probably originally native to N. Amer. Numerous infraspecific taxa are often defined on the distribution and orientation of the hairs. (O. europaea; O. corniculata, misapplied; Xanthoxalis stricta; X. bushii; X. cymosa; X. rufa)
An upright herb. It has an underground stem or rhizome. It has a taproot. It is hairy. The stems are 30 cm tall. They form roots at the nodes. The leaves have 3 heart shaped leaflets. The leaflets have a crease in the centre. The flowers are yellow.
