Loading pre-emergent timing
Crabgrass preventer and fall poa annua timing based on current modeled soil temperature estimates for this location.
Modeled estimate
Soil is well above the crabgrass germination threshold, so a spring pre-emergent application no longer helps. Switch to a post-emergent strategy for visible weeds, and plan for the fall poa annua application described below.
Modeled for this location because a current station reading was unavailable. Confirm with a soil thermometer before applying.
Crabgrass and most summer annual weeds begin germinating when the 2-inch soil temperature sustains 55°F for 3–5 consecutive days. Pre-emergent herbicides, the products sold at retail as crabgrass preventer, create a chemical barrier at the soil surface that prevents weed seeds from sprouting. The barrier must be in place before germination begins.
Pre-emergent has a second season. Poa annua (annual bluegrass) and other winter annual weeds germinate in fall as the 2-inch soil temperature drops back through 70°F after the summer peak, with most germination in the 65–70°F falling range. A fall application ahead of that crossing stops poa annua the same way a spring application stops crabgrass.
The Charlotte lawn care schedule tracks this window live against daily station readings. For products, rates, and the germination research behind the thresholds, see the fall pre-emergent timing guide.
Look for products containing prodiamine, dithiopyr, or pendimethalin. Dithiopyr has mild post-emergent properties and can suppress very young crabgrass (1–2 leaf stage) even if applied slightly late. Weed-and-feed products that pair fertilizer with a pre-emergent follow the same soil-temperature window: the preventer half only works if it is down before the 55°F crossing.
Full lawn care schedule for Charlotte →
Spring pre-emergent herbicide guide →
Enter your city or ZIP code to see current 2-inch soil temperatures and find out whether the crabgrass prevention window is still open.