There are several products on the market being used as natural turfgrass weed killer. Because of the toxic effects chemical herbicides have on the environment and water contamination more natural methods of weed control are becoming more popular among homeowners. Iron based weed killers, corn gluten meal, and vinegar.
Iron based weed killer is composed of a liquid form iron which is used to treat micro deficiencies in plants which is bound to a chelating agent making it readily available for plant uptake causing iron oxidation. When applied the the weed plants will dry out, turn black and die within hours of application. Iron based weed killer is safe on warm season turfgrasses St. Augustine grass, zoysia grass, bermuda grass, centipede grass, and bahia grass. These products may cause a darkening of grass leaf blades but the color will usually recover within a few days to a week. The compound is applied to actively growing weeds in the Spring and Fall when temperatures do not exceed 85 degrees. 3 applications in Spring every 21 days and 2 applications every 21 days in Fall has yielded the best results. Commercial brands like Iron X and Fiesta are available for application on new sod installation in Jacksonville Florida.
Corn gluten meal is a bi-product of the corn milling process and used as a natural turfgrass weed killer. Its N-P-K ratio is 8-1-0 and thus used as a weed and feed product. The corn gluten meal is applied at a rate of 20-40 pounds per 1500 square feet. Once applied must be watered in to be effective. Because corn gluten meal is a premergent herbicide meaning it inhibits the growth of weeds at the seed level by drying out the plant causing it to die quickly after germination. Because it works in this way it is less effective after heavy rains. It will not kill existing weeds. It should be applied twice a year once in the Spring and again in the Fall.
Use vinegar with caution. Although it will kill weeds it will kill your grass to in the same way round up works by applying it to the leaves and drying in the sun. It should be used as a spot treatment and not over your entire lawn. Vinegar acts as a great natural turfgrass weed killer for spot treatments.