Weed killer that controls all major broadleaf weeds, including dandelion, chickweed, and clover (see product label for complete list). Does not harm existing lawns This product is rainfast in 6 hours, so it will not wash off. Visible results in just hours. Kills tough weeds and the weed roots. For best results, mow before treating weeds. Spray in spring when weeds are small and growing, or in fall when many problem weeds germinate. Treating in fall will eliminate many of next year's weeds. If certain tough weeds are not dead within 3 weeks, repeat spot treatment. Read the entire label before using. Active ingredients: 2,4D, MCPP, and Dicamba.