Hottonia palustris

Hottonia palustris, the Water Violet, is a native of temperate Europe and western Asia where it inhabits clear, still or slow-moving lakes, ditches, and bog pools with cool, soft, nutrient-poor water. In spring it sends up emergent flower spikes bearing pale lilac or white blossoms, one of the most beautiful aquatic flowering events in the temperate zone. Submerged, its stems carry whorls of finely divided, pinnate leaves that resemble feathers, creating a distinctive and elegant underwater appearance. The plant is a true cool-water species, thriving below 22°C and declining when temperatures climb into the tropical range. In the aquarium it is challenging due to its narrow temperature requirement and intolerance of hard, alkaline water. It is best suited to unheated or lightly cooled tanks designed as European temperate biotopes. When conditions are correct, it grows at a moderate rate and can be a spectacular specimen. Hottonia palustris is an advanced plant for dedicated hobbyists who value botanical authenticity and are willing to maintain precise cold-water conditions.

Placement Use in the mid-to-background of cool-water aquariums or unheated setups. Plant in small groups of 4–6 stems. Also suitable for outdoor tubs in temperate climates.

Lighting Moderate lighting (30–50 PAR) is adequate. This plant does not appreciate intense tropical-strength lighting, which combines poorly with the warm temperatures it generates. Natural daylight cycles are beneficial.

CO2 & Fertilisation CO2 injection at low-to-moderate levels (10–20 ppm) can help, but the plant is sensitive to sudden pH swings. Nutrient requirements are low; light micronutrient dosing monthly is usually sufficient.

Propagation Top cuttings 8–12 cm long can be replanted after trimming. The plant also forms vegetative side shoots in good conditions. Rooting is slow and may take 2–3 weeks.

Trimming Trim sparingly; this plant grows slowly and does not recover quickly from heavy cutting. Remove spent lower leaves and dead material as they arise. Trim tops only when the plant approaches the surface.