Hydrocotyle sibthorpioides aka Lawn Marshpennywort

Hydrocotyle sibthorpioides is known as lawn pennywort or water pennywort. It is a small perennial that creeps across damp ground. The RHS places it in the Araliaceae family. Plants For A Future lists China and Japan as its native range. Useful Tropical Plants reports a wider range across Africa and Asia, reaching eastern Australia. It grows in shady lowlands, along streams, and in wet forest grassland. It is not native to Britain or Ireland.

This plant forms a close mat rather than upright growth. It reaches about 0.33 feet [0.1 metres] in height. Garden spread ranges from 0.33–1.64 feet [0.1–0.5 metres]. Useful Tropical Plants also describes clumps that spread beyond their stated width. Plants take two to five years to reach mature size. The small leaves range from round to kidney-shaped. They have shallow lobes and teeth along their edges. The RHS lists the foliage as deciduous. Tiny green flowers grow in small groups from late spring into summer. Insects pollinate the flowers, and the plant is self-fertile.

Grow lawn pennywort in sun or part shade. Its soil must stay moist throughout the growing period. It suits bog beds and the edges of ponds. It can also grow beneath shallow water. The RHS gives a maximum depth of 0.82 feet [0.25 metres]. Clay, loam, sand, and chalk are all suitable soil types. It tolerates acid, neutral, and alkaline soils, including poorly drained ground. The RHS rates its UK hardiness as H4. Plants For A Future lists USDA zones 5–9.

Its low mat suits damp spaces where ground cover is needed. The RHS classes it as a low-maintenance plant. Divide clumps to make more plants. Cut back growth often to keep its spread in check. Sources differ on its weed risk. Plants For A Future records no weed potential. Useful Tropical Plants reports weeds in damp lawns and warns of invasive growth there. The RHS reports few pest problems but lists mint rust as a possible disease.

The leaves and whole plant have recorded food uses. People eat it uncooked or cook it as a green. Its scent resembles parsley. Both food-use sources report no known hazards, though this does not establish pet safety. Traditional medicine uses include plant juice for fever. People also apply plant paste to wounds and boils. These records describe past uses, not proof that such treatments work.