Selective herbicide for the control of Winter Grass in lawn turf. Winter Grass Killer has been specifically developed to eradicate the highly common weed found in home lawns. You need to treat it as early as possible in its lifecycle. The more it matures, the more difficult it is to eradicate, and can often resist other weed sprays. Expect to treat Winter Grass for a few years running as the seed banks will take some time to deplete their stocks in the soil.