Virginia Buttonweed

What is Virginia buttonweed?

Virginia buttonweed is a deep-rooted, mat-forming perennial in the madder family and one of the most troublesome broadleaf lawn weeds in the Southeast. It is a native plant, but in wet, thin lawns it spreads into dense mats that can smother turf. Virginia buttonweed identification is straightforward once you know the signs: glossy leaves in opposite pairs with no leaf stalks, small white four-pointed star flowers tucked against the stem, and, by late summer, leaves splotched yellow by a virus.

What makes it so frustrating is how many ways it can come back. It spreads by seed, by rhizomes, and by stem and root pieces that mowers and string trimmers scatter around the yard, and those pieces root readily in moist soil. Hand-pulling leaves fragments behind that grow into new plants, and plants coming up from roots or stems are not stopped by any preemergence herbicide. It tolerates mowing down to about half an inch, and Clemson Extension notes that bringing it under control can take two years of treatments.

Virginia Buttonweed identification: what to look for

Kneel down and look where the leaves meet the stem. Buttonweed leaves sit right on the stem in opposite pairs, joined across the stem by a fringed flap of tissue. Look for the small white flowers in those joints and, later, the hairy green fruit. Tug a runner and you will find it anchored to a thick, branched root system.

• Leaves: Opposite, stalkless and lance-shaped, slightly thickened, shiny dark green on top and paler underneath. Edges can feel slightly rough and sometimes turn reddish.
• Leaf joints: A fringed stipule joins each leaf pair across the stem, and there is a small fleshy appendage where the leaves attach.
• Virus mottling: In late summer many leaves turn a blotchy yellow-green from a virus, which makes patches easy to spot from across the yard.
• Flowers: White and tubular with four petals spread into a star, sometimes streaked pink at the center, borne singly or in pairs in the leaf joints.
• Stems and fruit: Branched, low and spreading, occasionally hairy, and rooting at the nodes. Fruit is green, hairy, ridged and oval.
• Roots: Deep and extensive: fibrous roots arise from a fleshy, highly branched taproot, and rhizomes spread underground. Broken root pieces regrow.

Where it grows in the United States

Virginia buttonweed is native to the lower 48 states and is found from New Jersey west to Missouri and south into the Gulf Coast states. It is a troublesome lawn weed across the southeastern United States, and Clemson Extension reports it has recently become one of the more common lawn weeds in South Carolina.

Water is the key. It thrives in poorly drained spots and in lawns kept too wet by heavy rain or frequent irrigation, and overwatering during the growing season leaves a lawn far more open to invasion. Compacted soil and thin, stressed turf give it room to get started, and once a mat forms, mowing spreads stem pieces that root wherever the soil stays moist. Extension programs address it in bermudagrass, centipedegrass, St. Augustinegrass, zoysiagrass and tall fescue lawns alike.

Virginia Buttonweed look-alikes

A few plants get mixed up with it:

• Poorjoe (Diodia teres): A close relative with a similar low habit and small four-part flowers. Poorjoe is a summer annual with much narrower leaves, and its stems do not root at the nodes. Virginia buttonweed is a perennial with wider leaves and stems that root as they spread.
• Florida pusley (Richardia scabra): Also has opposite leaves and white tubular flowers, but it is an annual with noticeably hairy stems and leaves, a shallow root system, and flowers bunched in clusters at the stem tips. Buttonweed flowers sit singly or in pairs along the stem.

How to get rid of Virginia buttonweed

Pulling, digging and mowing: Hand-pulling does not work, because root and stem fragments left in the soil resprout, and digging rarely gets all of the deep, branched roots. Mowing too low stresses the grass and scatters stem pieces, so avoid scalping. Bagging and removing clippings from infested areas cuts down on seed and stem pieces being spread. Where buttonweed has taken over a large area and little grass is left, killing the patch and then resodding or reseeding is often more practical than trying to clean it up plant by plant.

Cultural control matters most, because the right conditions keep it from coming back.

• Fix drainage problems and water deeply but infrequently so the surface dries between waterings; overwatering invites buttonweed.
• Core aerate while your turf is actively growing to relieve compaction and improve drainage, and steer foot traffic away from thin areas.
• Mow at the correct height for your grass, raising it somewhat while buttonweed is establishing, and mow often enough to avoid scalping.
• Fertilize and lime according to a soil test, and dethatch if thatch builds up past about half an inch.
• Bag clippings from infested areas so you are not spreading seed and stem pieces.

Herbicides: Plan on a program, not a single spray; Clemson Extension notes it can take two years. Preemergence herbicides give poor control: indaziflam, isoxaben and oxadiazon may stop some seedlings, inconsistently, and none stops plants growing from roots or stems. In warm-season lawns the strongest options are sulfonylurea-based: metsulfuron, trifloxysulfuron (bermudagrass and zoysiagrass only), metsulfuron with sulfentrazone, and a combination of thiencarbazone, iodosulfuron and dicamba. Clemson advises starting in spring as plants green up and repeating four to six weeks later, while University of Georgia found these sulfonylureas work better in warm summer weather than in spring; either way, repeats are usually needed and late-summer plants are tougher. Except for the thiencarbazone combination, wait until warm-season turf has fully greened up. These sulfonylureas injure tall fescue; fescue options include combinations of 2,4-D, dicamba and MCPP, clopyralid with triclopyr, and fluroxypyr with 2,4-D and dicamba, avoiding heavy summer stress. Hold off when temperatures will pass about 85 to 90°F, depending on the product. Use products labeled for your turf species, and follow the label, which is the law. If you hire someone to spray, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Keeping it from coming back

Prevention starts with water. Buttonweed thrives where soil stays wet, so fix low spots and poor drainage and water deeply and infrequently. Keep turf dense with proper mowing, soil-test-based fertilizing and liming, and core aeration where soil is compacted.

Catch it early. Spring treatments kill seedlings and young plants before they knit into mats. Bag clippings when mowing infested areas and clean mowers and trimmers afterward so stem pieces do not root elsewhere.

Questions we get about Virginia buttonweed

Similar weeds

Florida PusleyRichardia scabraBurcloverMedicago polymorphaChamberbitterPhyllanthus urinaria