Some of you in the deep south are already in the window to apply your pre-emergent, the rest of us are on the cusp or are just outside the window. Get your Pre-emergent herbicide down when your 5 day soil temp average is about 50 degrees and climbing. Weed seed begins to germinate around the 55 degree mark.
How a pre-emergent works: Once applied and it has been watered in (rain or irrigation), the herbicide forms a "barrier" that will prune off new root growth from newly sprouted seedlings.
How much do I apply and how long it works in the soil:
Granular Prodiamine 0-0-7 Pre-Emergent
Granularly spread with a fertilizer spreader.
Apply at 3 lbs per 1000 sq ft and again the same application 6 weeks later. This will give you protection into the Summer. Each application will give you approx 3 months of protection and the overlap in applications is intentional.
If you'd rather spray your herbicide like me, check out the Prodiamine 65 WDG.
Add 5.2 grams of product per gallon of water to cover 1000 sq ft of lawn. Repeat this same rate again in 6 weeks to extend your protection into the Summer Months. Again, you'll have about 3 months of protection in each application. This is the best bang for your buck!