Pre emergent crabgrass treatment timing

Asked March 28, 2013, 6:45 PM EDT

Is it time to apply pre emergent crabgrass killer in Denver this year or should I wait? What are the signs that indicate the time is right? I've heard watching for certain trees to begin flowering is one way.


Denver County Colorado

1 Response

Ground/soil temp. of 55 degrees usually coincides with forsythia blooming and is a good time to apply pre emergent crabgrass killer. I've attached a CSU fact sheet that should prove helpful. Also here is excerpt from another fact sheet: Use slow release fertilizers such as sulfur-coated urea, meythlene urea, IBDU, or other synthetic organic fertilizer. 4. Mow lawns at 2 ½ - 3” height, removing no more than 1/3 of the lawn’s height at each mowing. Lawns mowed shorter than 2 ½” are more susceptible to disease, drought, and insect problems. Sharpen mower blades at least once per year. 5. Control dandelions and other broadleaf weeds in spring (mid-April to early June) and late summer/fall (end of August to October). Use pre-emergent herbicides to control annual grasses such as crabgrass. For crabgrass, apply prior to April 15th. 6. Insects and diseases are usually secondary problems in a homeowner’s lawn. Manage insects and diseases only after the above practices have been implemented.