Depending upon the pre-emergence herbicide product used, Kansas gardeners should spray the product in March or April. Applying an additional application of the herbicide eight weeks later, may be required to kill any weeds that germinate late in the season. Applying a pre-emergent herbicide in fall, controls crabgrass germination the following spring.
About this Author
Joyce Starr is a freelance writer from Florida and owns a landscaping company and garden center. She has published articles about camping in Florida, lawncare, gardening and writes for a local gardening newsletter. She shares her love and knowledge of the outdoors and nature through her writing.