This product is advertised by Scotts as being safe for St Augustine grass. Approximately seven days after applying this product to my lawn, which is St Augustine grass, the grass began to die. Within two weeks, any part of my lawn which had been treated with this product was completely dead including the root system itself. The product was applied within the guidelines as far as application rate and air temperature, as specified on the applicator. A check of the web indicates Scotts has been aware of this problem at least a far back as 2003 but continues to market this product as safe for St. Augustine grass.