When battling weeds, you must know thy enemy. Weeds are generally defined as any unwanted plant growing in the lawn or landscape. Weeds are categorized first as broadleaf or grassy. Next one must determine if it’s an annual or perennial. The next step in classification is to whether the weed is a summer or winter cycle. The weed elimination plan depends on what we are dealing with.
Perennial Grassy Weeds- these are the most difficult type of weeds to get a handle on. Dallisgrass, orchardgrass , poa trivialis, nutsedge, and bahaia are the ones we face here in the Piedmont area of North and South Carolina.
Annual Weeds- These weeds are relatively easy to control before they germinate with a pre-emergent program. Crabgrass, lespedeza, spurge, poa annua and henbit are quite common in Fescue and Bermuda turf
The biggest issues many face right now are the annual grassy (crabgrass) and annual broadleaf weeds (spurge/lespedeza). These weeds germinate in the spring, mature over the summer, sets seed and dies in the fall. Lawns that did not receive pre-emergent treatments in the spring, are right now loaded with annual weeds. I saw the first annual weed germination in late March this year. So unless that first pre-emergent was applied before that date, expect to see issues now. In this case an ounce of prevention is worth a pound of cure.
Once we hit Mid September, all of the plants energy is geared towards seed production because of its annual nature. The weeds will not absorb any herbicide. They can not be effectively controlled. These weeds are basically dying on their own at this time of year. The cooler it gets at night, the quicker they die. There is absolutely no sense in even trying to use herbicide now.
For Fescue lawns requiring seeding this fall all you need to do is “scalp” the lawn down with the mower on the lowest setting. This will effectively stop any re-growth and allow for good seeding results.