Leaves alternate, cauline or radical; lamina ± circular to lanceolate, margins toothed, crenate or ± entire, petiolate; stipules present, usually leafy.
Flowers solitary on axillary scapes with a pair of bracteoles near or below the middle. Sepals produced into small basal appendages. Lower petal spurred or pouched at base, lateral petals often bearded within. Anthers with a flat membranous appendage; the 2 lowest anthers with a spur at the base. Ovary glabrous or hairy; style usually bent.
| | Key to the genus Viola | |
| 1 | Annual or biennial; stipules to 4 cm long, green, deeply lobed; lower petal broad-cuneate | Viola arvensis |
| 1* | Perennials; stipules small, often brownish, translucent; lower petal ovate to linear-oblong | 2 |
| 2 | Plants not stoloniferous but stems sometimes elongated and decumbent; lower petal spurred; flowers scentless; styles thickened towards apex | 3 |
| 2* | Plants stoloniferous, stems rarely elongated; lower petal shallowly pouched but lacking a spur or if spurred then flowers sweetly scented; style not apically thickened | 4 |
| 3 | Stems lax, elongated; leaves cauline, lamina ovate to circular, cordate at base; corolla white, rarely pale violet | Viola caleyana |
| 3* | Stems erect, short; leaves radical, lamina lanceolate to oblong, the base cuneate or shallowly cordate; corolla violet to almost white, yellow at base | Viola betonicifolia |
| 4 | Petiole with short deflexed hairs, flowers strongly scented; lower petal spurred; capsule hairy | Viola odorata |
| 4* | Petiole glabrous, or if hairy the hairs not deflexed; flowers scentless or faintly scented; lower petal shallowly pouched but not spurred; capsule usually glabrous | 5 |
| 5 | Flowers mostly discolorous, petals 7–10 mm long; leaves with lamina reniform to more or less circular, mostly truncate or cordate at base | 6 |
| 5* | Flowers usually concolourous, petals less than 7 mm long; leaves with lamina ovate to rhombic, base cuneate and tapering into petiole | 7 |
| 6 | Leaves reniform to semicircular, more often wider than longer; flowers weakly to strongly discolourous bright to pale violet with white or pale violet tips, rarely concolourous; anther glands purplish or dull green, found in moderately dry to moist sites (not swamps) particularly forest habitats | Viola hederacea |
| 6* | Leaves orbicular with a deep sinus, flowers strongly discolourous, bright violet with prominent white tips; anther glands whitish (never purplish), found on coastal headlands and in lowland swamps and rainforest or moist sclerophyll forest margins | Viola banksii |
| 7 | Flower scapes 3–8 cm long, usually exceeding the leaves; flowers pale mauve to white, petals usually 4–7 mm long | Viola sieberiana |
| 7* | Flower scapes usually shorter than or scarcely exceeding the leaves; flowers blackish violet or cream, petals less than 4 mm long | 8 |
| 8 | Corolla blackish violet, lower petal c. 2 mm wide, obovate to elliptic | Viola fuscoviolacea |
| 8* | Corolla cream, often with a purplish tinge towards the centre; lower petal c. 1 mm wide, linear to oblong | Viola cleistogamoides |
