Answer: Crabgrass is an annual weed that will die down when the weather cools. But it will leave hundreds of seeds in its wake. There is no product that will eliminate the crabgrass and not harm your St. Augustine so the best defense is to keep it from sprouting in the first place. Crabgrass starts germinating when soil temperatures are 50 to 55 degrees F for ten or more days and germination can take place over a 6 week period. Pre-emergence herbicides provide excellent weed control for crabgrass but they last only about 30 days. A second application might have to be made to keep your lawn a little more crabgrass free. At this point, you might want to try raking it out or hand pulling. Next spring use the pre-emergent, reapplying in 30 days. That should keep the crabgrass under control. Proper lawn maintenance practices can limit crabgrass invasions. A dense stand of turfgrass prevents the weed from germinating and establishing. Fertilize at the end of May and remember that fall fertilizing, overseeding, aeration and thatch control can also limit spring weed problems. Best wishes with your lawn.
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