Knapweed Herbicide

Knapweeds are seed producing annuals and perennials which are commonly found in meadows and along streambanks. Luckily for prairie gardeners, knapweeds respond to spray herbicides.

Types

• There are three main types of knapweeds which become problematic for gardeners and landscapers in the United States, including diffuse knapweed, spotted knapweed and Russian knapweed, according to the Colorado State University. All types of knapweed blossom from July to September with white or purple flowers.

Control Options

• Small knapweed infestations are easily controlled with topical herbicides, according to North Dakota State University. Some suggested herbicides for knotted and diffuse knapweed include picloram, dicamba and clopyralid plus 2,4-D.

Applications

• Add 2 oz. of liquid herbicide to 1 gallon of water and spray onto the weeds with a hand-held sprayer. Additionally, spray about 10 to 15 feet away from the plants in a circle to kill weeds, according to North Dakota State University.