Answer: Crabgrass is a warm-season annual weed, meaning it reproduces by seeds. The best way to have a crabgrass-free lawn is to prevent it from ever showing up in the first place. You can achieve this is by applying pre-emergent herbicides to your lawn in the early spring. When the top two to three inches of topsoil reach about sixty degrees Fahrenheit, the crabgrass seeds will first germinate. Crabgrass will then produce seeds for the purpose of reproduction from mid-summer till autumn. Although the crabgrass will die out when the weather turns cold, the seeds it leaves behind will sprout the following summer. So, the only option available now is to pull it out, roots and all and take plugs or sprigs from you St. Augustine to fill in the bare spots. Next spring apply a pre-emergent to prevent the crabgrass seeds from sprouting and you should be rid of the weed. Best wishes with your lawn!
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