Weeds are unwanted, opportunistic plants that can invade lawn environments when grass growth is weak and unhealthy. The best method of weed prevention is cultivating an optimum environment for the growth of lawn grass that will effectively out-compete any weed invaders. However, if environmental controls alone are insufficient, weed herbicides can be used to aid in the prevention and removal of lawn weeds.
Selective, pre-emergent herbicides are methods of weed prevention that target specific annual grassy and broadleaf weeds before germination. Pre-emergent herbicides should be sprayed over the lawn surface several weeks before seed germination. They are ineffective after germination. Examples of selective, pre-emergent herbicide chemicals include trifluralin, bensulide, simizine and oryzalin. Read the product label to determine which weed type is targeted by a specific product.
Selective, post-emergent herbicides are methods of weed removal that target specific weed varieties after seed germination. After weed growth is visible through the turfgrass, post-emergent herbicides should be applied directly on the weed foliage. Examples of selective, post-emergent herbicide chemicals include dicamba, fluazifop-butyl and sethoxydim.
Non-selective, post-emergent herbicides provide a general solution to weed removal by targeting a wide variety of weed species after they have matured. Some collateral damage to surrounding plants and grass is possible due to misdirected spraying during application and chemical leaching through the topsoil. Examples of non-selective, post-emergent herbicide chemicals include glyphosate and triclpyr.