Dollarweed (pennywort) in warm-season lawns—wet-site ID vs dichondra
Identify dollarweed / pennywort (Hydrocotyle): silver-dollar leaves with a center-attached stalk, why wet sites and overwatering favor it, dichondra look-alike clues, and culture-first control before label chemistry.
Markdown version for AI agents and offline reading.
Round, shiny, lily-pad leaves popping up in low spots of a St. Augustine, zoysia, bermuda, or centipede lawn are often dollarweed—also called pennywort—in the genus Hydrocotyle. Clemson, NC State, LSU AgCenter, and UF/IFAS describe the same homeowner pattern: a warm-season perennial that thrives in moist to wet soil, spreads by seeds, rhizomes, and (in some species) tubers, and signals that the site stays wetter than the turf needs.
This is an ID and expectations guide for a typical DIY yard—not a product prescription or a remote diagnosis. Confirm odd look-alikes with county extension when chemistry is on the table.
Key takeaways
- Dollarweed ≠ dollar spot. Dollarweed is a broadleaf weed; dollar spot is a fungal disease with hourglass leaf lesions—different problem, different tools.
- Petiole attaches at the center of the leaf underside (umbrella / miniature lily pad). Dichondra attaches at the leaf margin—Clemson’s classic look-alike check.
- Presence usually means excess moisture: poor drainage, low spots, or irrigation that keeps the surface wet (UF research and Clemson both emphasize cutting water frequency as a first lever).
- Complete eradication is not a realistic DIY goal (Clemson); aim to limit the infestation while you fix wetness and thicken turf.
- Chemistry is grass-species and label dependent—three-ways, atrazine (where labeled), metsulfuron, and other actives appear in extension tables; read your label for St. Augustine / centipede rate cuts and temperature limits.
How to recognize dollarweed
| Clue | Dollarweed (Hydrocotyle) | Common mix-ups |
|---|---|---|
| Leaf shape | Round / silver-dollar, often 1–2 inches, bright green, fleshy, scalloped edge | Dichondra: similar round leaf but petiole at the edge, not center |
| Petiole | Attaches at center of underside → umbrella look | Grasses and nutsedge lack this round umbrella leaf |
| Habit | Low mat; can float in standing water | Prostrate spurge has milky sap and opposite oval leaves |
| Spread | Seeds + rhizomes (+ tubers in some accounts) | Annual summer mats that die with frost behave differently |
| Site | Moist, wet, poorly drained, over-irrigated | Hot dry thin turf more often hosts spurge or crabgrass |
A cheap illuminated hand lens helps confirm the center petiole attachment in the field. As an Amazon Associate, Lawn Care Journal LLC earns from qualifying purchases.
Flowers are typically small and white, clustered on stalks (LSU notes summer flowering). NC State highlights Hydrocotyle umbellata as a common wet-site species that can literally float.
Why midsummer wet lawns light up with “dollars”
Thunderstorms, heavy irrigation, shaded low corners, and compacted soils that hold water create the microclimate dollarweed loves. Clemson cites University of Florida work showing dollarweed declined when irrigation frequency was reduced—before anyone reached for a jug. That lines up with the broader deep, infrequent watering habit: wet the root zone, then let the surface dry, instead of nightly misting that keeps the upper inch soggy.
Warm-season lawns that look thin from chinch bugs, scalping, or shade also leave gaps dollarweed can colonize once moisture returns. Fixing only the weed while the lawn stays weak and wet is a temporary cosmetic win.
What a homeowner can actually do
- Audit moisture first—stand in the patch after rain or a sprinkler cycle. If water ponds or soil stays mud-soft for days, improve drainage, redirect downspouts, and cut redundant irrigation. Measure applied water with cans or a lawn rain gauge so “one inch a week” is real, not a timer guess—full method: rain gauge and soil probe.
- Hand-dig small patches—LSU stresses digging rhizomes, not just snapping leaves. Moist soil and a soil knife / weeder help; leaving underground stems invites regrowth.
- Thicken desirable turf—proper mowing height and fertility for your grass type (see Zoysia / St. Augustine spring care and bermuda green-up) outcompete many wet-site weeds once moisture is moderated.
- Fill bare spots after cleanup—Clemson notes bare patches left when dollarweed dies are open invitations; plug or sod with the same species when conditions allow.
- Use chemistry only after ID and label match—late spring after full warm-season green-up, on small actively growing plants, is the usual extension timing window. Effectiveness drops as plants mature.
Herbicide framing—educational, label is the law
Extension fact sheets list example actives that may control or suppress dollarweed on specific warm-season grasses (for example three-way mixes with 2,4-D + MCPP/MCPA + dicamba, atrazine on labeled St. Augustine/centipede programs, imazaquin, metsulfuron, or modern warm-season broadleaf mixes). Clemson warns that 2,4-D rates are often reduced on St. Augustine and centipede, that many postemergence products should not run during spring transition, and that three-ways are commonly avoided when air temperatures exceed about 90 °F. LSU highlights metsulfuron as highly effective on dollarweed in their guidance—with repeat applications sometimes needed—and still requires correct turf tolerance on your label.
Do not import a cool-season broadleaf schedule onto St. Augustine without reading the bag. Pet and family re-entry: follow pet-safe timing after products.
A retail search for dollarweed lawn weed killer or a calibrated hose-end / tank sprayer is a shopping starting point only after ID, grass-species checks, and label reading—not a substitute for extension rates or state registration.
Honest framing—control, not eradication
Clemson’s homeowner framing is worth repeating: eradication is not practical; control to a tolerable level is. Dollarweed’s underground spread and love of wet soil mean a single summer spray without drainage and irrigation changes usually resets next wet spell. Pair cultural fixes with optional labeled chemistry and multi-season patience.
If the same wet pocket also hosts yellow nutsedge, treat them as related moisture stories with different chemistry—nutsedge is a sedge; dollarweed is a broadleaf—Hydrocotyle umbrella leaves vs triangular stems. Coarse grass clumps returning year after year in those same wet lanes are often dallisgrass, not crabgrass—dig for short ringed rhizomes before you buy another annual grassy killer.
What to journal in wet weeks
Log where mats appear, whether soil stayed saturated, irrigation run times vs rain-gauge inches, grass species, and any product used (active ingredients + temperature that day). That map turns next summer’s “random dollars” into a drainage and timer project. Lawn Care Journal for iPhone and iPad is built for those notes; download on the App Store. Optional in-app Assistant is educational only—not a weed diagnosis.
Related reads: Virginia buttonweed late-July last call, summer watering, yellow nutsedge, dallisgrass vs crabgrass, prostrate spurge, chinch bugs and armyworms, dollar spot vs brown patch (different “dollar”), Zoysia / St. Augustine care. More DIY topics: articles index. App help: Support.