Answer: A healthy lawn that is properly fertilized, mowed, and irrigated will typically out-compete most weeds. However, some degree of weed control is often required to supplement even the best cultural practices.
Some weeds can be chemically controlled after they have emerged. Others, particularly grassy weeds, are better controlled "pre-emergence." You need to know where the weed pressure is and what the weeds are. You then need to select the right product for control and to apply it at the right time.
For pre-emergence crabgrass control, look for a product containing pendimethalin (available under multiple brand names). Apply this at label rates around the first of February in south Florida, mid-February in central Florida, and the first of March in north Florida. Note that there are no chemicals currently available to control grassy weeds in St. Augustinegrass.
For St. Augustinegrass lawns, atrazine is a commonly used herbicide for control of many broadleaf weeds. Be careful not to apply this when temperatures are high (> 85?)--it may injure the grass.
Slow-release fertilizers are generally better for a lawn than fertilizers that release their nutrients quickly during the first rain.
The first application of fertilizer to St. Augustinegrass should be made in spring when the grass is 50% green OR when soil temperatures are above 65 degrees F.
Fertilize St. Augustinegrass every six weeks thereafter until mid-September.
Good luck with your lawn!
Q&A Library Searching Tips