Dollarweed Control in Mississippi Lawns and Ornamentals

Hydrocotyle, better known locally as dollarweed or pennywort, is a rhizomatous perennial with umbrella-like, long-stalked, scallop-margined, waxy leaves. The petiole (stem) is found in the center of the leaf. This characteristic helps define it from Dichondra, which has a C-shaped, smooth-edged leaf, with the petiole found at the edge of the C indentation. Hydrocotyle species in Mississippi include H. bonariensis, H. prolifera, H. ranunculoides, H. sibthorpiodes, H. umbellate, and H. verticillata. Dollarweed is most often associated with moist to wet sites.

Cultural Control

Whether in ornamental beds or turf, proper cultural management that favors desired plant material is the basis of all weed control programs. Previous research conducted in Florida indicates that reducing irrigation frequency may decrease dollarweed densities. Since dollarweed prefers wet conditions, practice proper irrigation (not too much, not too little, and infrequent rather than every day). Remember, warm-season turfgrasses only need roughly 1 to 1.5 inch of irrigation/precipitation a week during the summer growing months. An inch applied weekly ensures deep rooting and more drought-tolerant turf. Make sure that soil drainage is adequate. Renovation of areas in order to improve surface drainage may be required. Another suggestion is that ornamental beds be mulched to approximately 3 inches of thickness.

Homeowners should be aware that complete eradication of this weed is impractical. Although chemical options exist, they are limited, especially without proper licensing. For these reasons, periodic hand removal of dollarweed is often the most effective control measure.

Chemical Control in Ornamentals

Dollarweed is a perennial that spreads vegetatively by rhizomes (vine-like runners). Applying a preemergence herbicide (those herbicides that prevent germination of seedlings) is recommended for regular bed maintenance but may provide limited control of this particular weed. Gallery (isoxaben), a preemergence herbicide, is labeled for use around many ornamental species. Image (imazaquin), a postemergence herbicide (those herbicides that control existing stands of the weed after seedling emergence) lists dollarweed control with repeat applications, and it can be used around some ornamentals. Read the labels carefully for specific use applications. Glyphosate (Round-up, Eraser, Touchdown, and others) can be applied postemergence; however, do not allow it to contact ornamentals because this chemistry is nonselective (it kills plants indiscriminately). Also keep in mind that many commercial products contain glyphosate, a slow-acting herbicide, plus a fast-acting herbicide like diquat. Glyphosate alone may be more effective at killing plant roots, but it requires time to translocate throughout the plant.