Virginia buttonweed

Virginia buttonweed (Diodia virginiana) is a low, sprawling perennial broadleaf weed with prostrate to spreading branched stems that radiate outward and root at the nodes, forming dense mats in turf. Its leaves are opposite, lance-shaped to elliptical, lacking petioles (sessile), joined across the stem by a membranous structure, slightly thickened and rough along the margins, dark green above and lighter green beneath, and the foliage often shows a yellow mottling or yellow-green discoloration caused by a virus. Small, white, four-petaled, star-shaped flowers form in the leaf axils, and the plant produces a distinctive green, ridged, oval to button-shaped fruit (the source of the common name). Its deep, fleshy taproot and ability to regenerate from stem and root fragments distinguish it from many shallower-rooted broadleaf weeds.

Virginia buttonweed forms dense, prostrate mats that smother and crowd out desirable turfgrass, creating unsightly patches that disrupt the uniformity of the lawn and resist mowing because the low stems stay below the blade. The frequent virus-induced yellow mottling of its foliage adds to the off-color, ragged appearance, and as patches expand they reduce turf density and leave a coarse, weedy stand. Because it tolerates close mowing and regenerates from fragments, infestations steadily worsen and become a chronic, hard-to-eliminate blemish, particularly in wet areas of the turf.

Virginia buttonweed is a deep-rooted herbaceous perennial that reproduces both by seed and vegetatively, which is a major reason it is so persistent. It regenerates readily from pieces of stem and root left behind after mowing or pulling, and it spreads by seed produced both in the showy above-ground flowers and in self-pollinating flowers borne below the soil surface. The plant emerges and grows through the warm season from a robust perennial root system that survives winter and resprouts each spring, allowing established patches to expand year after year.

Virginia buttonweed is a major weed of warm, humid regions, especially the southeastern United States, and is strongly favored by wet, poorly drained, or over-irrigated sites. It thrives in moist low areas, ditches, and lawns that stay damp, and it tolerates close mowing, which lets it persist in maintained turf where taller weeds would be cut out. Its preference for moisture means chronically wet spots, leaky irrigation, and poor drainage are common starting points for infestations, from which it spreads by rooting stems and by seed and fragment movement during mowing.