When to Plant Squash (Summer) in Arizona
Zucchini and yellow squash are the garden's most generous producers. You'll be sharing with neighbors by midsummer.
The Short Answer
Arizona Frost Dates
Your planting dates depend on which part of Arizona you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern Arizona (Flagstaff) | 4b, 5a, 5b, 6a | May 15 - Jun 5 | Sep 15 - Oct 10 |
| Central Arizona (Phoenix) | 9a, 9b, 10a | Jan 15 - Feb 10 | Dec 1 - Dec 20 |
| Southern Arizona (Tucson) | 8b, 9a, 9b | Feb 1 - Feb 25 | Nov 20 - Dec 15 |
Squash (Summer) Planting Schedule for Arizona
Northern Arizona (Flagstaff) (Zones 4b, 5a, 5b, 6a)
Average last frost: May 15 - Jun 5 · Average first frost: Sep 15 - Oct 10
Central Arizona (Phoenix) (Zones 9a, 9b, 10a)
Average last frost: Jan 15 - Feb 10 · Average first frost: Dec 1 - Dec 20
Southern Arizona (Tucson) (Zones 8b, 9a, 9b)
Average last frost: Feb 1 - Feb 25 · Average first frost: Nov 20 - Dec 15
Growing Squash (Summer) in Arizona
Squash (Summer) in Arizona's Climate
Squash grows during the cooler months in subtropical zones. Plant from September through February. Summer squash matures quickly enough to succeed even in Florida's compressed cool window. Pickle worm is a devastating fruit pest in the Deep South that northern growers never encounter.
Soil Considerations for Arizona
Alkaline, mineral-rich desert soils. Low organic matter. Heavy amendment with compost essential. Caliche layers may need to be broken. Make sure soil has warmed to at least 60°F before planting squash (summer) outside.
Arizona Climate & Growing Season
Extreme heat in summer lowlands. Two planting seasons in Phoenix — spring and fall (summer is too hot). High elevation has traditional cold-climate seasons. Squash (Summer) cannot tolerate any frost, so wait until all frost danger has passed before transplanting outside. Watch local forecasts carefully in spring.
Growing season length varies across Arizona: Northern Arizona (Flagstaff) (4b, 5a, 5b, 6a) has a last frost around May 15 - Jun 5, while Southern Arizona (Tucson) (8b, 9a, 9b) sees frost end around Feb 1 - Feb 25. This difference matters for squash (summer) — transplant timing shifts by several weeks across the state.
Growing Tips
Harvest when fruits are 6-8 inches long for best flavor. Larger squash become seedy and tough.
Companion Planting
Plant squash (summer) alongside these companions for better growth:
Keep squash (summer) away from:
The Bottom Line
Last reviewed: March 29, 2026