Common lespedeza

Common lespedeza, also called Japanese clover, is a low, prostrate summer annual legume with wiry, freely branching, dark stems that radiate outward and hug the ground, often forming a flattened mat. Each leaf is divided into three small, oblong, smooth leaflets with a prominent central vein and numerous parallel side veins, giving the leaflets a distinctly lined look that helps separate it from true clovers. Small pink-to-purple flowers form singly in the leaf axils. Because the wiry stems grow tight to the soil, the plant frequently escapes the mower. The trifoliate leaves and tough, branching stems distinguish it from black medic and clover.

Common lespedeza forms wiry, prostrate mats that crowd out turfgrass and create coarse, dark patches with a different texture and color than the surrounding stand, degrading uniformity especially in mid- to late summer. Because the stems lie below mower height, the weed persists and spreads while the desirable grass is thinning under heat and drought stress, and the freely branching mats leave thin, bare areas when the annual dies back at frost.

Common lespedeza is a warm-season summer annual that reproduces solely by seed. Seedlings emerge from the soil seed bank in early spring as soil warms, the plant develops and spreads through the summer, flowers and sets seed in mid- to late summer, and dies with the first frost. As a legume it fixes atmospheric nitrogen, which lets it persist on poor sites, and its prolific seed production replenishes the seed bank to ensure re-infestation the following season.

Lespedeza is strongly associated with low-fertility soils and thin, weak turf, and it commonly invades lawns, roadsides, and droughty, compacted, or poorly maintained areas where the desirable stand cannot compete. It tolerates close mowing and drought, exploiting the open canopy and lean conditions that suppress turfgrass. It is most troublesome across the southern United States, extending north to New Jersey and west to Texas and Kansas, and it tends to fill in the gaps created by summer stress on cool-season lawns and by low maintenance generally.