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Hydrocharis spp.
Overview
Hydrocharis spp. is a genus of small floating aquatics in the frogbit family, Hydrocharitaceae, with two or three species native to ponds, ditches, and slow streams of Europe, Asia, and Africa. The plants float free on the surface or root loosely in shallow mud, sending out runners that bud off new rosettes, so a few plants can cover open water in a season. Each rosette carries rounded to kidney-shaped leaves 0.5-2.5 inches (1.5-6 cm) wide on long stalks, glossy green above with a spongy purple-tinged underside that aids buoyancy. In summer small three-petalled white flowers with a yellow centre open just above the water, the sexes on separate plants. The plants overwinter as dense turions that sink to the bed and rise again in spring. H. morsus-ranae, European frogbit, has naturalised in parts of North America, where mats can shade and crowd native plants and slow water flow. The genus needs still, sheltered, nutrient-rich fresh water in sun and declines in fast or deep water.
Native Range
Native to still and slow-moving fresh waters of Europe, temperate and tropical Asia, and Africa; H. morsus-ranae has naturalised in northern North America.Suggested Uses
Grown in container ponds, wildlife ponds, and still water features in regions where it is not restricted, as floating cover and shade. The floating mats reduce algae by shading the water and give cover to pond life. It is kept out of plantings in areas where it is listed as invasive.How to Identify
Appearance
Size & Dimensions
Height1" - 2"
Width/Spread4" - 1'
Bloom Information
Flowering runs through summer, about June to August. The small white three-petalled flowers open just above the water for a few days each. Male and female flowers occur on separate plants, so seed is set only where both are present.
Detailed Descriptions
Flower Description
White with yellow centreFoliage Description
Glossy greenGrowing Conditions
Sun Requirements
Requires 4-8 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Hydrocharis spp. grows on still, sheltered, nutrient-rich fresh water in full sun to light shade and spreads quickly by runners in warm conditions. It needs calm water out of strong current and wind, which break up the floating mats. The plants draw nutrients directly from the water, so no rooting medium or feeding is required. They are hardy and overwinter as turions on the pond bed, regrowing in spring. In small ponds the mats are thinned by hand to keep open water and light for submerged plants. Because H. morsus-ranae is invasive in some regions, its sale and movement are regulated there.Pruning
No pruning is needed. Excess rosettes are netted or raked off the surface through summer to limit cover, and removed plants are kept out of natural waterways. Turions can be cleared in autumn to reduce the following year growth.Container Growing
✓ Suitable for container growing
Minimum container size: 3 gallons