When to Apply Pre-Emergent in Arizona
The best time to apply pre-emergent in Arizona is late january to mid-february. Use the GDD tracker below for precise timing based on your ZIP code.
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Pre-Emergent Timing in Arizona
Spring Application
Late January to mid-February
Target: when soil temperature reaches 55°F at 4-inch depth for several consecutive days
Fall Application
Late August to early September
Prevents winter annual weeds like annual bluegrass (Poa annua)
Common Grass Types in Arizona
Arizona has a warm-season climate, meaning soil temperatures rise early in the year. Crabgrass and other summer annual weeds can begin germinating as early as late winter, so early pre-emergent application is critical.
Pre-Emergent Tips for Arizona
- In the Phoenix metro and southern desert areas, apply as early as late January.
- Northern Arizona (Flagstaff, Prescott) may not need pre-emergent until March or April.
- Bermuda grass lawns overseeded with ryegrass need careful timing to avoid harming the ryegrass.
- A second application 8-10 weeks after the first provides season-long protection.
- Water in the pre-emergent with at least 0.5 inches of irrigation within 24 hours.
Local Expert Resources
For research-backed lawn care advice specific to Arizona, visit your state's university extension service:
University of Arizona Cooperative ExtensionFrequently Asked Questions
When should I apply pre-emergent in Arizona?
In Arizona, the best time to apply pre-emergent is late january to mid-february. Use Growing Degree Days (GDD) tracking for precise timing based on your local soil temperature.
What grass types are common in Arizona?
Common grass types in Arizona include Bermuda Grass, Perennial Ryegrass, Buffalo Grass. Arizona is in USDA Hardiness Zones 4b-10b.
What is the best pre-emergent herbicide for Arizona?
For most lawns in Arizona, Prodiamine (Prodiamine 65 WDG) provides the longest-lasting barrier at 8+ months. If you are applying late, Dithiopyr (Dimension 2EW) is a better choice because it offers early post-emergent control on young crabgrass. Compare all pre-emergent options.
What soil temperature triggers pre-emergent application in Arizona?
Apply pre-emergent when soil temperature at 4-inch depth reaches 55°F for several consecutive days. In Arizona, this typically corresponds to 150–200 Growing Degree Days (base 50°F) accumulated from January 1.
Should I apply pre-emergent in the fall in Arizona?
Yes. In Arizona, a fall pre-emergent application (late august to early september) prevents winter annual weeds like Poa annua (annual bluegrass) and henbit from establishing.
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