Best methods for controlling crabgrass and other annual grassy weeds.
Early spring is the best time to control summer annual grassy weeds like crabgrass (Digitaria spp), foxtail (Setaria spp), goosegrass (Elusineindica), and others like Japanese Stiltgrass (Microstegium vimineum). Being annuals, these weeds die each fall and winter then re-germinate from seed in the spring when the soil temperatures approach 55° F. The best method of controlling summer annual grassy weeds is with a pre-emergent herbicide because once crabgrass, foxtail and other annual grassy weeds germinate and get established, they are extremely difficult to control. This is an essential part of our Early Spring Lawn Treatment.
There are several management practices you can utilize to help minimize crabgrass and other annual grassy weed “pressure” in your lawn. The first is good mowing practices. We find that poor mowing is the primary reason for heavy crabgrass infestations. Avoid scalping the lawn. Never cut more than 1/3 of the grass blade off at any one mowing and never mow shorter than 3” after the grass starts growing in the spring. Second, avoid spring aeration, dethatching or any other activity that disturbs the soil during peak crabgrass season. Also avoid seeding in the spring as well. The pre-emergent herbicide inhibits turfgrass seed as well as annual grassy weed seeds.
Very rarely will we see 100% preventative control of crabgrass. Usually some will break through, especially in thin and bare spots. In those cases, you can hand-pull it if it is just a few plants, otherwise you can use post-emergent herbicides.
Some might say, “What’s wrong with having crabgrass and foxtail in my lawn? At least it is green during the summer.”
While the weeds may be green during the summer, they will die out and brown in the fall. Worse yet, the areas that were overrun with crabgrass then become bare spots. Those areas would also be subject to soil erosion during the winter and thus potentially harming the Chesapeake Bay. A thick lawn promoted by a responsible lawn care program with the proper use of fertilizer and weed control products is a great way for you to contribute to helping the Bay.
Mark Schlossberg is the President of ProLawnPlus in Baltimore, MD. He graduated from the University of Maryland in 1977 with a B.S. in agronomy. He is the President of the Maryland Association of Green Industries, and past president of the Maryland Turfgrass Council.