Leaves radical or cauline, mostly palmately compound, often with 3 leaflets; leaflets sessile or shortly petiolulate, entire or 2-lobed; stipules usually ciliate.
Inflorescences 1–many-flowered. Sepals and petals 5. Stamens 10. Carpels 5, united; ovary hairy inside loculii; styles 5, free.
A number of species are grown as ornamental plants. Some naturalized species are serious weeds of cultivated pastures.
| | Key to the species | |
| 1 | Aerial stem and branches absent or greatly reduced; leaves and peduncles radical | 2 |
| Aerial stem and branches erect, ascending or creeping; leaves often whorled; peduncles axillary | 10 |
| 2 | Petals yellow | 3 |
| Petals pale mauve, pink to purple, rarely white throughout
Back to 1 | 5 |
| 3 | Inflorescences 3–25-flowered; rhizome white and fleshy | Oxalis pes-caprae |
| Inflorescences 1-flowered; rhizome brown and papery
Back to 2 | 4 |
| 4 | Leaves 4–7-foliolate; leaflets narrow-elliptic to linear | Oxalis flava |
| Leaves 3-foliolate; leaflets oblong to obovate, never linear
Back to 3 | Oxalis perdicaria |
| 5 | Petioles densely hairy; hairs white; inflorescence 1-flowered, with flower on a peduncle that scarcely exceeds the leaves | Oxalis purpurea |
| Petioles glabrous or with scattered hairs; inflorescence mostly at least 3-flowered, with flowers on peduncles exceeding the leaves
Back to 2 | 6 |
| 6 | Numerous small bulbils produced | 7 |
| No small bulbils produced
Back to 5 | 9 |
| 7 | Leaflets transversely cuneate, with lobe apices 12–50 mm apart | Oxalis latifolia |
| Leaflets cuneate to obcordate, with lobe apices to 12 mm apart
Back to 6 | 8 |
| 8 | Petals 18–20 mm long; inflorescence 1–4-flowered; bulbils formed from old bulb on stolons to 15 cm long | Oxalis brasiliensis |
| Petals 12–18 mm long; inflorescence 8–15-flowered; bulbils formed from old bulbs, sessile
Back to 7 | Oxalis debilis |
| 9 | Bulbs ovoid, tapered; leaves borne on a short stem | Oxalis bowiei |
| Bulbs absent; leaves borne on a woody rhizome
Back to 6 | Oxalis articulata |
| 10 | Petals yellow, to 12 mm long; bulbils absent | 11 |
| Petals white, pink to mauve, 13–22 mm long; bulbils present
Back to 1 | 17 |
| 11 | Hairs on stem and branches mostly antrorse; stipules usually conspicuous, but not truncate | 12 |
| Hairs on stem and branches spreading or retrorse; stipules either inconspicuous, or scarious and truncate
Back to 10 | 15 |
| 12 | Taproot stout; fruits long and usually slender, 8–30 mm long, 1.5–2.5 mm diam., erect | Oxalis perennans |
| Taproot probably absent or only slightly developed; fruit long or short, but not slender and erect
Back to 11 | 13 |
| 13 | Leaflets cuneate-obcordate, appearing angular-shaped; fruit long, 15–18 mm long, often stout in the middle, 3–4 mm diam.; plant rather glaucous | Oxalis rubens |
| Leaflets cuneate-obovate; indumentum sparse or dense; fruit short and broad or if longer then straight-sided; plant green
Back to 12 | 14 |
| 14 | Fruit short and broad, 5–6.5 mm long, 2–3 mm diam., with simple hairs; apex tapering; seeds strongly ridged | Oxalis exilis |
| Fruit moderately long, 8–30 mm long, 1.5–2.5 mm diam., with flat septate hairs; apex abruptly narrowed; seeds almost smooth to shallowly ridged
Back to 13 | Oxalis thompsoniae |
| 15 | Fruit short and stout, 7–9 mm long, 3 mm diam.; branches long and trailing; leaves densely hairy | Oxalis chnoodes |
| Fruit long and relatively narrow, 8–16 mm long, 1.5–3 mm diam.; branches erect or trailing; leaves densely hairy or glabrescent
Back to 11 | 16 |
| 16 | Stipules keeled and inconspicuous; taproot stout and woody | Oxalis radicosa |
| Stipules truncate and obvious, usually thin and glabrous except for hairs at margin; taproot, if developed, not stout and woody
Back to 15 | Oxalis corniculata |
| 17 | Leaflets linear, bilobed with lobes c. 0.5 mm wide; bulbils formed on old bulb | Oxalis bifurca |
| Leaflets obcordate, bilobed with lobes 5–9 mm wide; bulbils formed on rhizome and in leaf axils
Back to 10 | Oxalis incarnata |
