How to Kill Stinkweed in Grass
Stinkweed grows between 2 and 24 inches high and has smooth green leaves. Small white flowers grow atop the stalk, usually in the summer. Stinkweed propagates from seed, which forms after flowering. One of two kinds of stinkweed may be infesting your lawn. Summer annual stinkweed begins to grow in early spring and flower in the summer. Winter annual stinkweed begins to grow in the fall, continues to grow into the spring and then flowers in the summer. Each can be killed in a similar manner, although timing the application of an herbicide will be different.
Pull up stinkweed. This is best done before the weeds flower and begin to seed and is easiest when the soil is wet. Dispose of the weed away from your grass. You can compost stinkweed if you did in fact pull the weeds before they flowered. Otherwise, they may seed and grow where you use the compost.
Apply an herbicide in the spring for summer stinkweed annuals. Use an herbicide, such as one that contains 2,4-D, amine or glyphosate. Be sure it is safe for use on lawns. Read the label on your herbicide and strictly follow the instructions for both dosing and application methods. Typically, you apply the herbicide in large even sweeping motions over top the grass where the stinkweed is growing.
Apply an herbicide in the fall for winter annual stinkweed. Use the same herbicides you used for summer annual stinkweed and again, read and follow label instructions.