Can I seed the lawn after applying crabgrass pre-emergence?

Prevent crabgrass pre-emergence prevents all grass and grassy weed seeds from germinating. However, you can grow grass seed above and through the vapor barrier of the herbicide by following these idiot proof steps on how to grow grass in barespots after you have applied crabgrass pre-emergent.

How to make Uncle’s “Seed Sandwich”

  • Locate your bare spots and rake clean any debris.
  • Apply Prevent over the entire lawn and water with ½ inch of water within 48 hours. 
  • Wait a minimum of 3 days, to allow for the pre-emergence herbicide to activate in the soil. Using a heavy rake scratch the soil surface of each bare spot. Disturbing the soil surface will break the weed killing vapor barrier created by the herbicide.
  • Cover each barespot with ½ inch of weed free PrimeraFC to protect the new seed from the herbicide.
  • Apply your new Grass Pad grass seed on top of this new layer of PrimeraFC.
  • Cover grass seed with an additional ¼ inch layer of PrimeraFCDO NOT USE TOPSOIL OR COMPOSTED PEATS. Topsoil  and composted peats are contaminated with weed seeds from the field it was taken. 
  • Keep consistently moist with frequent light waterings.
  • Mow as needed with a sharp blade on a day when the grass is not wet.

How does the Seed Sandwich work?

Turf grass seeds and weed grass seeds that are in or under the herbicide vapor barrier of Prevent are killed as the top shoot of the grass plant emerges from its seed coat at germination.  A layer of PrimeraFC lifts and holds the seed above the vapor barrier. This insulating layer allows the top shoot to grow up and the roots to grow down through the vapor barrier and into the soil and get established. 

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