Weeds & Grass Killer

Selective Herbicides

• Selective herbicides kill weeds without harming turf grass, according to the University of Rhode Island. These herbicides are chemically formulated to kill weeds not closely related to turf grass. For example, spraying a selective broadleaf herbicide near ornamental wildflowers can kill those flowers, but not harm grass. Gardeners spraying their lawns with excessive amounts of selective herbicide cause lawn damage. Use the right amount and at the right time. Types of selective herbicide consist of active ingredients such as mecoprop, 2,4-D plus and dicamba.

Using Selective Herbicide

• The best time to kill perennial broadleaf weeds with selective herbicide is between Aug. 15 to Oct. 15 and May 1 to June 1, according to the University of Minnesota. Gardeners should target annual, perennial and biennial broadleaf weeds with selective herbicide spray. You can tell the difference between a broadleaf weed and your grass by the way broadleaf weeds are more colorful and grass has triangular tips. Repeat the selective herbicide applications every 20 to 30 days, according to the University of Minnesota.

Nonselective Herbicides

• Nonselective herbicides kill anything, including turf grass. This herbicide type is used during lawn renovations, in areas where grass isn't growing and to spot-treat perennial grassy areas. Choose nonselective herbicides with active ingredients such as diquat, glufosinate and glyphosate, according to the University of Rhode Island. As these herbicides kill any type of vegetation, use care when spraying the yard or around ornamental plants.

Using Nonselective Herbicides

• Wait for a 48-hour window of dry weather before applying these sprays. To treat perennial grassy weeds, wet their foliage before applying the spray, so that the spray sticks and dos not run off into your grass. Spray broadleaf weeds when they are dry. Laying a piece of plastic around these weeds prevents the spray from contacting nearby grass. Control weeds growing above grass by spraying nonselective herbicide on a rag. Wrap the rag around a rake and paint the herbicide on their foliage.