Comarum palustre aka Marsh Cinquefoil

Comarum palustre, or marsh cinquefoil, belongs to the rose family. Sources also list it under the name Potentilla palustris. It grows across the subarctic and temperate Northern Hemisphere. Its range includes parts of Asia, North America and Greenland. The RHS also records it as native to Britain and Ireland. Wild habitats include marshes, bogs, acid fens and wet heaths. These wet places help explain its main need in gardens.

This deciduous perennial has a woody base and spreads by rhizomes. It forms clumps with loose, upright stems. Garden plants reach about 0.3–1.6 feet (0.1–0.5 metres) tall. Their spread reaches about 1.6–3.3 feet (0.5–1 metre). The grey-green leaves each have five to seven leaflets. Plants lose their leaves for winter. They take around two to five years to reach full size. Allow space for the clump to reach its full width.

Deep red flowers open in loose groups in early summer. Large sepals carry a red flush around each flower. These sepals add to the dark colour of the display. The flowers also provide a source of red dye. The RHS describes the fruit as ornamental and warns against eating it. Its warning applies to people and pets. It also advises gloves and other protective gear when handling plants.

Grow marsh cinquefoil in full sun with soil that stays wet. The RHS recommends neutral or alkaline soil, including clay and loam. Its wild habitats also include acidic sites. A bog garden suits its need for lasting moisture. It also fits wildlife gardens and informal planting schemes. The RHS rates its cold hardiness as H7. Plants For A Future lists USDA zones 3–7. Plants need no pruning and have few reported pest problems. Honey fungus may cause disease. Propagate by seed or divide plants in spring or autumn.

Plants For A Future records dried leaves as a tea substitute. This use does not establish that every plant part is safe. That source reports no known hazards, unlike the RHS fruit warning. It gives the plant a low food-use rating. It also records past medicinal use of the astringent root. A root decoction was used for dysentery and stomach cramps. These records describe past use, not proven treatment. The roots also yield tannin.