I received the following question last week through the Cooperative Extension “Ask the Expert” system. It illustrates how confusing the lawn care industry is to homeowners trying to do the right thing on their lawns:
I have a turf-based lawn. I intend to weed and feed in early March. I know that my lawn needs a pre-emergent to control Bermuda/crabgrass. However, there are also other weeds, e.g., clover and other varieties. What weed control do you recommend and when should it be applied?
First, forget about “weed and feed” products. They do not make sense for your lawn. Apply most of the fertilizer your lawn needs in the fall and if anything, only apply ½ lb of nitrogen/ 1000 square feet (that equals 5 lbs of a 10-10-10 fertilizer, which is 10% nitrogen) in the spring. Apply that small amount of fertilizer in March and no later than April 15. Apply weed control later in the spring; so bundling those two products will not work.
This person wants to use a preemergent to control unwanted grasses. That is great for crabgrass. As an annual grass, it must germinate each year, so if you can prevent its emergence with an herbicide you can reduce the crabgrass in your lawn later in the season. We recommend applying crabgrass preemergent products when forsythia is blooming, usually April, after you have applied spring fertilizer. The other grass mentioned is bermudagrass—a perennial grass that cannot be controlled with a preemergent herbicide. Bermudagrass is a warm season grass, so it will not start growing until late spring. It cannot be controlled with a preemergent since its roots are alive and ready to burst into action with warm soil temperatures. It cannot really be controlled with a selective herbicide either since there is very little difference between bermudagrass and the desirable grass in your lawn—except you like one and dislike the other. For bermudagrass, we recommend spot treatment with a systemic herbicide that is non-selective (like glyphosate).
They also mention clover and other weeds. Clover is not an annual, so a preemergent herbicide will not control it. Instead, use a broadleaf herbicide specific for clover control (MCPP will work) once the clover is green and growing, but still young and susceptible to chemical control. When you use selective herbicides, you must know which weed you are controlling. For example 2,4-D products will control dandelions but not clover.
The best strategy for controlling weeds and maintaining a healthy lawn is to promote healthy turfgrass growth. Fertilize modestly, if at all, in the spring. Cut your grass at the appropriate height and frequency. Don’t remove more than one-third of the leaf blade at any single mowing. So, if you have a fescue lawn and you want to maintain it at a height of 3 inches, cut the grass when it reaches 4 ½ inches removing 1 ½ inches (one-third of the leaf blade). By following these guidelines, your grass is able to catch light and photosynthesize, producing its own food for healthy growth. Always use a sharp mower blade. Control weeds when they are young so they do not take over. Finally, apply most or all of the fertilizer required by your lawn in the fall (between late August and mid-October).
If you want to learn all about managing a healthy lawn, visit the Delaware Livable Lawns website. Learn how you can make your lawn livable. https://www.delawarelivablelawns.org/
If you want to learn more about horticulture in Delaware, follow my Instagram (sbartonhort).