When to Plant Squash in Arizona
Published: April 21, 2026
Arizona gardeners in Zone 9b enjoy an extended 50-week growing season for squash. Warm-climate gardeners can grow two squash crops — a spring planting and a fall planting — with summer heat as the main challenge to work around. This guide gives exact dates for Arizona based on your local frost calendar.
Squash Planting Dates for Arizona
| Start seeds indoors | December 25–January 1 |
| Last frost (average) | January 15 |
| Transplant outdoors | January 22–February 1 |
| Direct sow outdoors | January 22–February 1 |
| Expect first harvest | March 8 – March 28 |
| Fall crop start | October 22–November 1 |
| Fall harvest | December 6 |
| First fall frost (average) | December 31 |
Dates above assume Zone 9b, the most common zone in Arizona. Gardeners in cooler San Tan Valley (Zone 7b) plant 1–2 weeks later; warmer Tucson (Zone 9a) can plant 1–2 weeks earlier.
Growing Squash in Arizona's Climate
Arizona's warm Zone 9b climate gives squash more than enough heat — in fact, peak summer heat (95°F+) can shut down fruit set entirely. The solution most Arizona gardeners use is a two-season approach: a spring crop planted early, a harvest break during peak summer, and a fall crop planted July through August for October and November harvest.
Variety selection matters more in warm climates than most gardeners realize. Choose heat-tolerant varieties bred for Arizona-like conditions — local extension offices and nurseries stock these specifically. Afternoon shade cloth during July and August can be the difference between a working fall crop and total flower drop.
Common squash pests to watch for in Arizona include Squash Vine Borer and Squash Bug. The first line of defense is companion planting: Corn and Bush Beans planted nearby discourage several of these pests by confusing host-plant identification or repelling adults before they can lay eggs. Weekly garden walks in the early morning catch problems when they're still manageable.
Squash Garden Calendar for Arizona
| Month | Task | Notes |
|---|---|---|
| January | Transplant outdoors | Soil temp must be 65°F+; nighttime lows above 50°F |
| February | — | Off-season |
| March | First harvest window opens | Squash begins producing 45–65 days after transplant |
| April | — | Off-season |
| May ← | — | Off-season |
| June | Peak growth; water 1 inch/week | Monitor for pests daily; stake or support as needed |
| July | Start fall crop seeds | Fall transplants go in 10 weeks before first frost |
| August | — | Off-season |
| September | — | Off-season |
| October | Fall crop planting | Transplant or direct sow for fall harvest before frost |
| November | — | Off-season |
| December | Start seeds indoors | Use grow lights; warm soil to 70–75°F for best germination |
Squash Growing Tips for Arizona Gardeners
- •Plant only after soil is fully warm (65°F+) — cold soil rots seeds and creates disease-prone seedlings.
- •Squash vine borer kills plants from the inside in July–August in the eastern US; plant a backup crop in early July.
- •Arizona's summer heat shuts down squash flowering at 95°F+. Choose heat-tolerant varieties and use shade cloth from mid-June through August to preserve fruit set.
- •Arizona's fall crop is often more productive than spring — plant transplants in July after the worst heat, for October and November harvest as temperatures cool.
- •Hand-pollinate using a small brush if fruit falls off small — squash need bee visits for fruit set.
Companion Planting for Squash in Arizona
In Arizona's warm climate, planting squash with Corn and Bush Beans helps deter pests and improve soil. Avoid planting near Potato and Fennel, which inhibit squash growth through root chemistry or shared pest pressure. See the full squash companion planting guide for the complete list.
Squash Planting Dates by City in Arizona
Top cities in Arizona — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant squash in Arizona?
In Arizona (Zone 9b), start squash seeds indoors around December 25–January 1 and transplant outdoors around January 22–February 1 — 1 weeks after the state's average last frost of January 15.
What is the last frost date in Arizona?
Arizona's average last frost date is January 15 in the state's most common Zone 9b. Frost dates vary by city — higher elevations and northern counties run 1 to 3 weeks later than the state average. See the city list below for city-level frost dates.
Can I grow squash year-round in Arizona?
Not year-round — Arizona's cold season stops squash production. The squash season runs January 15 to December 31, roughly 50 weeks. A fall crop extends harvest into late autumn.
What squash varieties grow best in Arizona?
For Arizona's Zone 9b, Yellow Crookneck and Tromboncino tolerate heat and humidity well.
When do I start squash seeds indoors in Arizona?
Start squash seeds indoors in Arizona around December 25–January 1, which is 3 weeks before the state's average last frost of January 15. Use grow lights and keep soil temperatures at 70–75°F for fastest germination.