Dollarweed (Hydrocotyle spp.) also commonly called hydrocotyle, pennywort or marsh pennywort, is a warm-season, water-loving perennial weed that detracts from the attractive uniformity of a lawn. Various species of dollarweed, so named for the leaves that are the same size as silver dollar coins, are found across a broad range that extends from about U.S. Department of Agriculture plant hardiness zones 3 through 11. Dollarweed is very difficult to control, even with the use of herbicides, but certain practices can help to minimize the presence or spread of this persistent weed.
Hand pulling or digging out dollarweed is a feasible control method, especially where it is just beginning to invade an area or there are only a few plants. Dollarweed can spread using rhizomes and tubers as well as with seeds, so it is necessary to capture the entire root system and best to pull the plants up before they go to seed. It is much easier to pull these plants out without breaking the root system if the soil is moist from a recent rainfall or supplemental irrigation. Repeat pullings will likely be necessary to achieve satisfactory control.
Proper irrigation methods are key, since these weeds thrive in moist soils. They are, in fact, water-loving plants that can float and their presence generally indicates excessive moisture in the site. Lawns benefit from deep, occasional irrigation only when the top 1 to 2 inches of soil feel dry to the touch. About 1 inch of water weekly through rainfall and supplemental irrigation is usually sufficient when the grass is actively growing. Each irrigation should moisten the top 6 to 8 inches of soil.
Even if a lawn is rarely watered, excessive moisture in the soil can still present problems if drainage is poor. Minor soil drainage problems are often caused by compaction, which also negatively impacts grass growth. Using a hand-held or machine-driven aerator to pull up cores of soil about once per year, depending on the amount and type of traffic the site receives, alleviates compaction. Perpetually wet low spots are difficult to address in established lawns, since grade is easiest to correct prior to planting grass. One way to address very wet spots is to replace turf and invading weeds with a moisture-loving ground cover or ornamental grass that will grow vigorously in that spot.
Additional Grass Care Considerations
Dollarweed tends to invade thin, weakened turf, so providing a lawn with excellent care will help to crowd out dollar weed. Mowing the grass at the maximum height recommended for the species and never removing more than one-third of the grass blade height in a single mowing session minimizes injury to the grass plant and slows thatch accumulation. Three or four fertilizer applications per year that each supply the lawn with no more than 1 pound of nitrogen per 1,000 square feet of lawn when the grass is actively growing encourages dense, healthy growth.
- Clemson University Cooperative Extension Service: Dollarweed
- University of Florida IFAS Extension: Dollarweed
- University of Florida IFAS Extension: Dollarweed Doldrums
- USDA Natural Resources Conservation Service: Plants Profile for Hydrocotyle
- USDA Agricultural Research Service: USDA Plant Hardiness Zone Map
- University of California Statewide Integrated Pest Management Program: Weed Management in Lawns