This turf tip is part of a three part series on spring seeding.
Most turfgrass herbicides are intended for use on established grasses. Thus, herbicide use on newly planted grasses should be very conservative. If possible, wait until the grass has gone through several mowings or a full growing season before using chemical weed control. However, as described in Part II of this turf tip (add part II link here) there are some postemergence broadleaf herbicides that are safer on newly seeded turf including Drive (quinclorac), Tenacity (mesotrione), SquareOne (quinclorac + carfentrazone), and Imprelis (aminocyclopyrachlor).
If weed competition is severe enough to warrant herbicide use, a good rule of thumb is to wait until a recently seeded lawn has been mown two to three times before using the three-way herbicides (2,4-D + dicamba + MCPP) or Q4 Plus (quinclorac + sulfentrazone + 2,4-D + dicamba), Onetime (quinclorac + MCPP + dicamba), or Solitare (quinclorac + sulfentrazone). See the label of the product you wish to use for complete directions.
Keep in mind that the best time to control weeds is in the fall. See our fall posting on broadleaf weed control for more information on fall application timings (http://www.agry.purdue.edu/turf/tips/2010/10182010_broadleafweeds.html ).
Just as with spring seeding dates, it is important that when turf is planted in the fall that new turf seedlings are mown 2-3 times before a fall postemergent herbicide application is made for broadleaf weeds or alternatively that a herbicide is used that is typically very safe on new seedling such as Drive (quinclorac), Tenacity (mesotrione), SquareOne (quinclorac + carfentrazone), or Imprelis (aminocyclopyrachlor).
Aaron Patton, Assistant Professor/Turfgrass Extension Specialist