When seeding new lawn kill tough weeds first Sometimes the best way to handle weeds in a new lawn is to take extra time and make the effort to control weeds before seeding.
That's advice to homeowners and back yard weedfighters from Leon Wrage, Extension weed specialist at South Dakota State University.
Before seeding is the only time to eliminate coarse perennial grasses like quackgrass and brome or tough weeds like field bindweed, the specialist said.
It's also possible to eliminate a great deal of the annual weed pressure from foxtail, pigweed, and kochia if seeding is delayed until fall.
If the new lawn is being established where a serious crabgrass problem existed, delaying seeding also will reduce that problem in the new seeding, Wrage said.
"There is always a desire to get new grass started � to avoid dust and mud � but if you are working into a weedy spot that had heavy uncontrolled growth last year, waiting may pay off," Wrage said.
"It also may be a good plan if you are completely renovating an old, weedy lawn."
To prepare for seeding this fall, allow weeds to grow with the lawn this spring, advised Wrage. Glyphosate, the generic name for Roundup, works well as an herbicide program. It's best to have several inches of growth before treating. The non-selective herbicide controls perennial grasses (lawn grasses included), and broadleaves, and also will take out emerged annuals, Wrage said. Shallow tillage will take out flushes of annuals.
Delay working for at least a week. The herbicide treatment can be repeated on spots that have regrowth of perennials. Annual weed flushes can be taken out with shallow cultivation.
"Efforts on some tough weeds can pay off and the areas can be readied in excellent condition for fall seeding," he concluded.