Updated: Apr 17, 2022
BY: Alice Marty, Mobile County Master Gardener I www.mobilecountymastergardeners.org
Definition of a weed. “A plant whose virtues have not yet been discovered.”
Ralph Waldo Emerson.
It’s that time of year again when the Mobile County Extension Office Home Grounds and Garden information phone line is heating up. The perennial weeds in our home lawns tend to green up before the grass, sticking out like sore thumbs. Homeowners are horrified to see the damage winter has inflicted on their yard. The war on weeds is about to renew itself for 2022.
Before beginning a weed control program, homeowners should realize that the complete eradication of any weed from the landscape is not practical. A more realistic approach is to control the weed by limiting the infestation to a tolerable level. A properly maintained landscape that is not stressed by insects, diseases, drought, nor nutrient imbalance is the best defense against weeds. Proper mowing height of lawns and a 3-inch-thick mulch layer around trees and shrubs will prevent the invasion of weeds.
Many Mobile County residents will bring weed samples to the Extension Agents and Master Gardeners at the Mobile County Extension office for identification. Correctly identifying a plant is vastly important to its removal. That is where things can get a little confusing at times. Dollarweed/pennywort can also be known as many flower, marsh pennywort, water pennywort, Indian pennywort, money plant, and navelwort. These are all the same plant: hydrocotyle umbellate.
Dollarweed’s name comes from its size and shape resembling a silver dollar. Pennywort’s name comes from the English genus hydrocotyle vulgaris, which is found growing in most parts of Europe. The leaves of this species are round and about the size of an English penny; hence the common name "pennywort."
Although having many names dollarweed is easy to identify. It is a native perennial weed that has bright green, rounded leaves with scalloped edges. The stems attach to the center of the leaf on long petioles. It is often confused with dichondra, which looks similar, but its leaves are attached to the kidney-shaped leaf’s edge. Small, white flowers bloom from July to August. The creeping stems root wherever their nodes touch the soil, increasing the number of plants. It spreads by seeds or rhizomes. Dollarweed grows in moist, shady lawns, gardens, and unplanted areas, and thrives in warm temperate regions of the United States. It is a member of the parsley family.
Dollarweed is a water-loving plant that can float. Its presence indicates excessive moisture in the area. Research at the University of Florida demonstrated a reduction in dollarweed just by reducing irrigation frequency. Monitoring moisture levels and evaluating irrigation are the first steps to controlling dollarweed. Established landscape plants and lawns require one inch of water a week for optimum growth, including both rain and irrigation. Discourage dollarweed by improving the drainage of the soil and reducing irrigation, thus decreasing the amount of water it receives.
To rid your yard of dollarweed, hand pulling can be easily done in beds but may be impractical for large areas. Carefully administered herbicides can be helpful. Before spring green-up, a pre-emergent broadleaf herbicide appropriately labeled for your turfgrass species may be applied (usually in February in our zone). Once the spring green-up has completed, use a post-emergence broadleaf herbicide appropriately labeled for your turfgrass species.
For best results, apply the post-emergence herbicide when dollarweed is actively growing and in the one-leaf to flower stage of growth. Reapply or use spot treatment within the following two weeks.
IMPORTANT: Be sure to read all directions on the label before using herbicide and carefully follow all precautions.