Ranunculus flammula aka Lesser Spearwort

Ranunculus flammula is a perennial in the buttercup family. Its names include lesser spearwort and creeping spearwort. It grows wild across Eurasia and North America. It is native to Britain and Ireland. In the wild, it grows beside lakes and ponds. It also grows in other wet ground and shallow water.

Garden size varies between sources. NC State gives heights of 0.5–1 foot [0.15–0.3 metres]. RHS gives 1.6–3.3 feet [0.5–1 metre]. Reported spreads range from 0.3–3 feet [0.1–0.9 metres]. Its reddish stems creep and take root at their nodes. They can form a thick mat of leaves and stems. In water, stems spread on or just below the surface. Some leaves stand partly upright; others lie near the ground. The green leaves range from oval to narrow and spear-shaped. Their surfaces may feel smooth or bear fine hairs. Some leaves have a red tint. The plant loses its leaves for winter.

Bright yellow flowers open in summer, starting in early summer. Each flower stands alone on a thin, upright stalk. Most flowers have five petals, though the number can vary. Yellow stamens crowd around green styles at the centre. Sources differ on flower size. NC State reports flowers about one-third inch across; RHS gives about four-fifths inch. Bees and flies visit the flowers. The brown fruit appears in summer. Flowers and creeping growth suit wet ground in wildlife gardens.

Grow this plant in full sun or part shade. It needs moist or wet ground and tolerates standing water. RHS recommends still or slow water, 0.5–0.7 feet [0.15–0.22 metres] deep. It accepts clay, loam, or sand across a broad pH range. It suits pond edges, rain gardens, and streamside sites. Growth proceeds at a moderate rate. RHS lists hardiness H7; NC State gives USDA zones 4–8. Sow ripe seed or divide plants in spring or late summer. Cut plants back once flowering ends.

NC State reports no major growing problems. RHS lists possible aphids, slugs, and snails. Powdery mildew, rust, and grey mould may also occur. All fresh parts are poisonous to people and pets. Eating them can cause mouth pain, vomiting, and diarrhoea. The sap can burn skin and cause blisters. Wear gloves when handling the plant. PFAF lists no known food use. It records medicinal use, but this does not establish safety.