Herbs, perennial, from thick caudices 0.5-2 cm or slender stolons. Leaves basal and cauline, simple; proximal leaves petiolate, distal leaves sessile or nearly so; cauline leaves alternate. Leaf blade unlobed, oblong-ovate to orbiculate-reniform or cordate, margins entire, dentate, or crenate. Inflorescences terminal or axillary, 1-6-flowered cymes or flowers solitary, to 22 cm; bracts leaflike, not forming involucre. Flowers bisexual, radially symmetric; sepals not persistent in fruit, 5-12, white, pinkish, yellow, or orange, plane, oval-orbiculate to narrowly obovate, 4-23 mm; petals absent; stamens 10-40; filaments filiform; staminodes absent between stamens and pistils; pistils 5-55, simple; ovules 15-35 per pistil; style 0.1-2 mm. Fruits follicles, aggregate, sessile or stipitate, linear-oblong to ellipsoid, sides prominently veined or not; beak terminal, straight or weakly curved, 0.2-2 mm. Seeds brown, elliptic to broadly elliptic, rugulose. x=8.

Distribution

Primarily temperate wetlands, worldwide.

Discussion

Species 10 (3 in the flora).

Selected References

Smit, P. G. 1973. A revision of Caltha (Ranunculaceae). Blumea 21: 119-150.

Lower Taxa

Caltha leptosepala, Caltha natans, Caltha palustris

Key

1	Stems leafless, or with 1 leaf; sepals white to yellow, not orange or pinkish.	Caltha leptosepala
1	Stems leafy; sepals white, yellow, or orange, or pinkish.	> 2
2	Stems creeping or floating, rooting at nodes; sepals white or pinkish, 4–7(–8) mm; follicles 20–55, bodies 3.2–6.5 mm; seeds 0.5–0.8 mm.	Caltha natans
2	Stems erect, or sprawling with age and then producing shoots and roots at nodes; sepals yellow or orange, (6–)10–25 mm; follicles 5–15(–25), bodies 8–15 mm; seeds 1.5–2.5 mm.	Caltha palustris