Weedol Lawn Weedkiller Liquid Concentrate stimulates the growth of broad-leaved weeds causing them to grow at a rate they simply cannot sustain, effectively dying of exhaustion and leaving your grass with space to grow without competition. Use on leafy weeds from April – September when they are actively growing. One treatment controls most common broad-leaved lawn weeds in one annual application without harming the grass. Use on all established lawns and grassy areas.