War on Weeds — Weeds are Everybody’s Problem
Common/European frogbit
Common/European frogbit (Hydrocharis morsus-ranae) is an aquatic annual native to Europe and northern Africa. It invades rivers, lakes, reservoirs and wetlands. It establishes particularly well when sheltered from currents and waves. Common frogbit is typically free-floating but when water is less than 2 feet deep it can root in soil. It spreads very quickly, forming large dense mats of vegetation that interfere with native ecosystems, recreation and irrigation.
Common frogbit leaves look like small lily pads (1/2-2 1/4 inch in diameter), with a round heart shape. Leaves are yellowish green on the top and purple on the bottom. Flowers are small, white, have three petals (1/2 inch in diameter) and have yellow centers. Its ability to spread vegetatively by stolons and fragmentation allows this weed to spread very quickly.
Integrated Pest Management (IPM) options
- Prevention — Learn to identify this plant. Remove all vegetation from boats and recreational equipment before transporting to a new body of water. Never dispose of aquarium contents in bodies of water. Report sightings to local authorities.
- Mechanical — When small infestations are present hand removal can be effective. Remove as much plant material as possible. This weed can reproduce from broken fragments.
- Cultural — Water drawdown during the winter or in the spring can help to control populations in small bodies of water.
- Chemical — Consult with local authorities before attempting to control this weed with herbicides. Special care should always be taken when using herbicides near bodies of water. Always read and follow herbicide label directions.
Idaho is a wonderful place with awesome natural resources, landscapes, agriculture and recreational opportunities. Weeds threaten all the things that we love about Idaho. To detect, contain and control weeds in Idaho we have declared “War on Weeds.” These short articles are designed to give a brief description of each species, an explanation about why it’s a problem, insights into identification and Integrated Pest Management control options. — Justin Hatch
View or Download (pdf)
- Common frogbit, 12-28
2024 (pdf)
- Bur buttercup, 1-22
- Buckhorn plantain, 1-29
- Kochia, 2-5
- Feathered mosquito fern, 2-12
- Flowering rush, 2-17
- Jointed goatgrass, 2-24
- Giant hogweed, 3-2
- Hoary alyssum, 3-9
- Hydrilla, 3-16
- Giant knotweed, 3-23
- Johnsongrass, 3-30
- Quackgrass toms, 4-6
- Meadow hawkweed, 4-13
- Meadow knapweed, 4-20
- Mediterranean sage, 4-29
- Milium, 5-6
- Orange hawkweed, 5-11
- Parrotfeather milfoil, 5-24
- Perennial pepperweed, 6-1
- Dryer's woad, 6-8
- Purple starthistle, 6-29
- Saltcedar, 7-6
- Black Henbane, 7-24
- Scotch Broom, 8-3
- Squarrose knapweed, 8-10
- Syrian beancaper, 8-17
- Tall hawkweed, 10-5
- Water chestnut, 10-12
- Russian thistle, 10-19
- Musk thistle, 10-26
- Water hyacinth, 11-2
- Yellow devil hawkweed, 11-9
- Yellow flag iris, 11-16
- Eurasian watermilfoil, 11-23
- Yellow floating heart, 11-30
- Yellow starthistle, 12-7
- Phragmites, 12-14
- Common frogbit, 12-28
Photo courtesy of Leslie J. Mehrhoff, University of Connecticut, Bugwood.org.