Here's an organic way to keep weeds out of your lawn. Nature's Guide Corn Gluten Meal interferes with the germination of seeds. Put it down early in the Spring (depending on the weather, between February 15 and March 15 in the Fort Worth area) and in the Fall (again depending on the weather, September 15 through October 15) and it'll keep the weeds out. It's also a great early season fertilizer. The spreadable version of the product is not as effective as a weed preventer, but it makes great all-nitrogen fertilizer.