Thick, lush lawns are beautiful, but weed pressures are sure to emerge this spring. Spring and summer annuals as well as perennial weeds can not only distort a picturesque lawn, but also thin your lawn and rob nutrients from our preferred fescue. Proper weed identification and good planning will keep the majority of your weeds at bay this year.
In Kentucky, we have several spring germinating weeds that are fairly easy to identify. Dandelion, henbit, chickweed, and purple deadnettle are some of the most common early weeds. Later, as the soil temperatures warm up, crabgrass and goose grass show up, often with a vengeance.
Identification is key to control. There are three basic types of weeds in our lawns; broadleaf weeds, grass-like weeds, and sedges. Just like the name implies, broadleaf weeds have broad leaves while grass like weeds have “blades” similar to fescue. Sedges are identified by a strong, protruding mid-rib creating a triangular blade. Knowing what weed you have and a little about its life cycle will help tremendously with determining the best control.
Typically with any lawn weed, control products are either pre-emergent or post-emergent. Most broadleaf weeds are best controlled post-emergently with a common herbicide 2,4-Dichlorophenoxyacetic acid, or 2,4-D for short. 2,4-D can be purchased in a concentrated liquid formulation, or an easier to use granular product in combination with a fertilizer. When applying a granular post-emergent herbicide, it is important to ensure the granular particles adhere to the leaf of the target weed. Applying the herbicide in the early morning when the lawn is damp is often the best time.
Pre-emergent herbicides are used to prevent the germination of many weeds but we apply it in lawns to target crabgrass and goose grass. Pre-emergents work by forming a layer just below the soil surface. As the weed germinates, it will come into contact with the herbicide and growth will stop before the weed reaches the surface. Pre-emergents are available in liquid formulations but most often homeowners utilize the granular formulation for easier application.
Properly timed applications of pre-emergent herbicides are most critical for best control. If the target weed has already germinated, it is too late to control with a pre-emergent. Crab grass and goose grass germinate as the soil temperature warms up and forsythia blooms are a good sign that the soil is getting warm enough for crabgrass to germinate. This spring watch for the forsythia blooms and apply your pre-emerge within the following 2 weeks. Always follow the label with any control product.
Proper weed identification and proper herbicide selection and application will help keep your lawn healthy. If you need help with weed identification or weed control, contact your local Extension Office and they can help direct you to the best resources.
Submitted by Andrew Rideout, Agent for Horticulture, Henderson Co. Cooperative Extension