Hydrocharis morsus-ranae
European frog-bit
Overview
Hydrocharis morsus-ranae is a small free-floating aquatic perennial that drifts on the surface of still fresh water, resembling a miniature water lily. Its rounded to kidney-shaped leaves are 0.4-2.4 inches (1-6 cm) across, glossy green, and held in rosettes that float on or just above the water, joined by slender stolons that bud off new plantlets. From June to August it bears small three-petalled white flowers 0.6-0.8 inch (15-20 mm) across with a yellow centre, held just above the surface. Male and female flowers grow on separate plants. The roots hang free in the water and do not reach the bottom in deeper sites. It grows in ponds, ditches, canals, and quiet backwaters across much of Europe and western Asia, favouring still, base-rich, nutrient-rich water. As autumn comes the plant forms dense winter buds called turions that sink and rest on the bottom, rising again in spring. It spreads quickly by stolons and turions and can blanket a still surface in one season. Outside its native range, in North America, it has become an aggressive invader of waterways. Its free-floating habit and kidney-shaped leaves separate it from rooted water lilies.
Native Range
Native to Europe and western Asia. It grows in still or slow fresh water, including ponds, ditches, canals, and quiet backwaters, on base-rich, nutrient-rich sites.Suggested Uses
Grown in wildlife ponds and still-water features for its floating leaves, summer flowers, and the surface cover it gives to pond life. It shades the water and shelters aquatic animals. It is kept to small, contained ponds because of its rapid spread.How to Identify
Appearance
Size & Dimensions
Height1" - 2"
Width/Spread1' - 2'
Bloom Information
Small white three-petalled flowers open from June to August just above the water surface. Male and female flowers are borne on separate plants, so seed set depends on both being present. The flowers are visited by small flies and other insects.
Detailed Descriptions
Flower Description
white with yellow centreFoliage Description
greenGrowing Conditions
Sun Requirements
Requires 4-10 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 morsus-ranae grows as a free-floating plant on still, base-rich fresh water in full sun to partial shade. It tolerates a water pH of about 6.5 to 8.0 and grows fastest in nutrient-rich, sheltered water. The plant spreads rapidly by stolons and overwintering turions, so it is thinned in small ponds to keep the surface open. It is hardy to USDA zone 4, surviving winter as resting buds on the pond floor. It needs no soil, drawing nutrients straight from the water. In closed waters it can cover the surface and shade out submerged plants.Pruning
Surplus floating rosettes can be netted off through the growing season to keep part of the surface clear. The plant dies back to sunken turions in autumn with no cutting needed. Removing plants before turions form limits its spread.Container Growing
✓ Suitable for container growing
Minimum container size: 5 gallons