Oxygenating pond plant
Water violet
Hottonia palustris
A native submerged aquatic (Hottonia palustris) that acts as a good oxygenator, grows in up to 60 cm of water and flowers in late spring (May–June); it needs clear, still or very slow-moving water and good water quality.
PLANT PROFILE
About Water violet
Water violet (Hottonia palustris) is a submerged aquatic plant native to Great Britain and Ireland, valued in garden ponds for its underwater foliage and upright flower spikes. The plant grows with stems and leaves entirely under (or just floating on) the water surface, with only the flower spike projecting above. RHS lists it as a good oxygenator and suitable for wildlife gardens, and Freshwater Habitats Trust describes it as characteristic of ponds, ditches and slow backwaters.
Cultivation guidance from RHS advises planting directly in margins or in baskets in clear, still or very slow-moving water in full sun. Mature plants are reported to tolerate up to 60 cm of water; a numeric planting depth for soil placement is not given in the supplied sources. Vegetative height is given by RHS as up to 0.1–0.5 m, while flower spikes can reach up to 80 cm according to Freshwater Habitats Trust. RHS gives a maximum spread of 0.5–1 m. Hottonia palustris is listed as H5 for hardiness by RHS.
Propagation is supported by RHS recommendations to divide in spring or grow from seed; RHS also notes that plants sometimes produce resting buds that sink to the bottom to overwinter and then produce fresh growth in spring. Maintenance is generally straightforward—RHS lists it under 'Low Maintenance' planting locations and states no pruning is required—but the species is very susceptible to poor water quality and can be smothered by filamentous algae. RHS also notes a possible pest, the false leaf-mining midge. Freshwater Habitats Trust highlights conservation concern and decline in parts of England, so keepers should be mindful of water quality and local conservation status.
Legislation-wise, Water violet appears in the schedules of The Wildlife (Northern Ireland) Order 1985 (Northern Ireland); no equivalent restriction for England, Wales or Scotland was identified in the supplied searches. Follow local guidance where relevant.
POND SUITABILITY