Fall is the time to control tough perennial broadleaf lawn weeds. Good moisture in most places in August will have set up good fall growth of perennial weeds. The target weeds in the fall are dandelion, ground ivy, creeping bell flower, field bindweed, and white clover. Ground ivy is also known as creeping charlie and field bindweed is often referred to as creeping jenny. Results in SDSU WEED project tests show fall timing has the best chance for excellent control of dandelion. Active new growth is important for good results. Let the grass grow up and delay mowing to get good growth. Spraying can start now anytime in September. For the toughest weeds like ground ivy and creeping bell flower make a repeat application as soon as your product's label allows; ideally in two weeks.
Fall works best for perennials as the herbicide moves better into the root. If you wait until a light frost other plants in the yard are less sensitive to drift. Apply with care and use low pressure and coarse droplets to reduce drift. Do not make applications if it is windy. Most broadleaf lawn products are a mixture of herbicide ingredients, they are available in several product brands. Check label guidelines in mixing and applying instructions. Treat now and see the results next spring.