Geum rivale (Water Avens)
Geum rivale, the water avens, is a flowering plant of the family Rosaceae. Other names for the plant are nodding avens, drooping avens, cure-all, water flower and Indian chocolate. It is native to much of Europe, with the exception of Mediterranean areas, as well as some parts of Central Asia and North America. In North America, it is known as purple avens. It grows in bogs and damp meadows, and produces nodding red flowers from May to September.
The plant is a native perennial of slow-draining or wet soils and can tolerate mildly acidic to calcareous conditions in full sun or under partial shade. Habitats include stream sides, pond edges, damp deciduous woodland and hay meadows.
G. rivale is pollinated primarily by bees, less often by flies and beetles. As the flower matures, elongation of the stamens ensures it self-fertilises if not already cross-pollinated. The flowers stigmas mature before the stamens. It begins flowering a little earlier than G. urbanum, so early pollinations will be within the gene-pool of the single species. The seeds of Water Avens are burr-like, and are distributed after being caught in the coats of rabbits and other small mammals, and by rhizomal growth
G. rivale is parasitised by Podosphaera aphanis – a conidial powdery mildew. Yellow spots on the living leaf may be caused by Peronospora gei – a downy mildew.
Geum urbanum hybridises fairly regularly with Geum rivale as they are closely related and occur together.
It is a component of Purple moor grass and rush pastures is a type of Biodiversity Action Plan habitat in the UK. It occurs on poorly drained neutral and acidic soils of the lowlands and upland fringe. It is found in the South West of England, especially in Devon.
Culture
Grow in moist to wet soils in full sun to part shade. Prefers moist, fertile soils in cool climates. Needs afternoon shade in hot, humid climates. Tends to struggle with both summer heat and humidity south of Zone 7 where it is not recommended for planting. Likes boggy and swampy conditions. Not always reliably winter hardy in areas north of Zone 5. Plants may be propagated by seed or division. Deadheading spent flowers will encourage additional bloom.
Noteworthy Characteristics
Geum rivale, commonly known as water avens, purple avens or chocolate root, is a clump-forming herbaceous perennial of the rose family that typically thrives in boggy areas including wet meadows and swamps. It is native to Eurasia and North America (Labrador to British Columbia south to New Jersey, West Virginia, northern Illinois, Minnesota and in the mountains to New Mexico). It typically grows to 8-18” tall and features showy, nodding, bell-shaped, 5-petaled flowers (to 1/2”), 2 to 5 flowers per stem, which bloom late spring into summer (late May to early August) and compound dark green leaves. The brownish-purple calyx of each flower surrounds its cream to purple-pink petals. Each pinnate leaf has 3 to 6 pairs of small, lateral, unequally-toothed leaflets (1/4 – 3/4”), with a very large terminal leaflet (1-2” diameter) which is usually over twice the size of the lateral leaflets. Good ground cover for cool wet areas where many other plants often struggle. Will grow well in non-boggy areas as long as soils are kept consistently moist.
Genus name is the classical Latin name of the group.
Specific epithet means growing by streams.
If plant rhizomes are boiled in water, the resulting liquid has a faint taste of chocolate, hence the common name of chocolate root.
Problems
No serious insect or disease problems. May be short-lived in heavy clay soils and/or hot summer climates.
Garden Uses
Mass in borders or rock gardens. Foliage makes an attractive ground cover after bloom.
