Overview
Hydrocotyle ranunculoides is a creeping, mat-forming aquatic perennial that roots in mud at the water's edge and trails out over the surface on floating stems. The shiny, rounded to kidney-shaped leaves are 2-7 cm (0.8-2.8 in) wide, with three to seven shallow lobes and scalloped edges, held just above the water on stalks 5-35 cm (2-14 in) long. Stems root at the nodes and branch freely, so a few fragments build into thick floating rafts that can blanket still and slow-moving water. The tiny flowers, greenish white and only 1-3 mm (0.04-0.12 in) across, gather in small clusters and are easy to miss. The plant spreads almost entirely by stem fragments, each piece able to start a new colony, which is why it has become a serious invasive weed of waterways in Britain and Europe. Dense mats cut light and oxygen to the water below and clog drainage. It is native to the Americas, but its sale and movement are banned across much of Europe.
Native Range
Hydrocotyle ranunculoides is native to North, Central, and South America, growing in ponds, ditches, and the slack margins of streams. Introduced to Europe through the aquatic trade, it is now banned from sale and listed as an invasive species in Britain and the European Union.Suggested Uses
In its native American range it is sometimes used as an oxygenating pond plant in contained water features. Elsewhere it has no garden use and is the target of control programmes. Its banned status and invasive spread rule it out of planting across Europe and many other regions.How to Identify
Appearance
Size & Dimensions
Height2" - 6"
Width/Spread2' - 10'
Bloom Information
Small greenish-white flowers appear from July to September (mid to late summer) in tight clusters on short stalks. The flowers are inconspicuous and set little viable seed in cool climates. Spread is driven by fragmenting stems rather than by flowers.
Detailed Descriptions
Foliage Description
glossy greenGrowing Conditions
Sun Requirements
Requires 4-12 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
Hydrocotyle ranunculoides grows in full sun to part shade in still or slow-moving fresh water and in wet mud at the margins, rooting in water up to about 60 cm (24 in) deep. It tolerates a wide pH from 6.0 to 8.0 and nutrient-rich water, where it grows fastest. The plant spreads explosively from fragments, so it is not planted in open ponds or waterways and is illegal to grow or move in many countries. Where it appears, mats are removed by hand or machine and disposed of away from water, since any fragment left behind regrows. It grows without care and outcompetes native aquatics. Repeated removal over seasons is needed to clear an infestation.Pruning
Floating mats are raked or netted out repeatedly through the growing season to check spread, with all fragments removed from the water. Cut or pulled material is composted well away from watercourses. No ornamental pruning applies, as the plant is managed for control rather than form.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
summer
Container Growing
✓ Suitable for container growing
Minimum container size: 3 gallons