Louisiana's warm, temperate environment is ideally suited for the growth of a wide variety of lawn weed species. Common lawn weeds of Louisiana fall into two categories: broad-leaved and grass-like weeds. Broad-leaved weeds do not resemble lawn grass and are distinctly visible and identifiable by their broad leaves and flowering stems. Grass-like weeds, as the name implies, look very similar to lawn grass and in some instances, actually are a proper grass species.
Annual sedge (Cyperus brevifolius) is a grass-like perennial that forms dense mats of dark-green leaves up to 6 inches thick. Annual sedge spreads by above-ground seeds and underground rhizomes. Overwatered, moist lawn areas are prone to annual sedge.
Bristly mallow (Modiola caroliniana) is a broad-leaved perennial with light-green, shiny leaves forming on multiple stems and nodes. During early spring, orange-red flowers are visible. Pull out by hand or apply a post-emergence herbicide on existing weeds.
Black medic (Medicago lupulina) is a broad-leaved, summer annual with green, clover-like foliage and yellow flowers. Black medic thrives in infertile, low nitrogen soils and produces seeds near the base, allowing propagation even in a regularly mowed lawn. Add nitrogen rich fertilizer to your lawn to help prevent black medic weeds from forming.
Broadleaf plantain (Plantago major) is a broad-leaved, low growing, perennial weed with wide, green leaves arching outward from a central stem. Broadleaf plantains grow most rapidly during the late summer and produce a perforated seed pod growing vertically from the central node. Broadleaf plantains can be physically removed by hand or sprayed with a selective broadleaf herbicide.
Chamber bitter (Phyllanthus urinaria) is a grass-like, warm-season annual, with grooved, vertical, green leaves. This weed propagates by exploding seed pods, which scatter seeds around the lawn. Pull isolated weeds by hand, as necessary.