When to Plant Spinach in Arizona
Published: April 24, 2026
Arizona gardeners in Zone 9b enjoy an extended 50-week growing season for spinach. Cool-season crops like spinach do best in fall, winter, and early spring in Arizona — the hot summers bolt these plants before they can be harvested. This guide gives exact dates for Arizona based on your local frost calendar.
Spinach Planting Dates for Arizona
| Start seeds indoors | Year-round |
| Last frost (average) | January 15 |
| Direct sow outdoors | December 11–21 |
| Expect first harvest | January 20 – January 30 |
| Fall crop start | November 19–29 |
| Fall harvest | December 29 |
| 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.
⚠ One of the earliest spring vegetables — sow 4–6 weeks before last frost. Bolts in heat above 75°F. Plant again in late summer for a fall harvest.
Growing Spinach in Arizona's Climate
Arizona's warm Zone 9b climate makes spinach a fall, winter, and early spring crop rather than a summer one. The cool-season window runs roughly October through April in Arizona — plant outside this window and the spinach will bolt (send up a flower stalk and turn bitter) before it produces a harvestable crop.
Succession planting stretches the spinach harvest window. Sow small amounts every two weeks from October through February — you will have staggered harvests rather than a single wave to process all at once. Bolt-resistant varieties extend the usable window an extra three to four weeks into warming weather.
Common spinach pests to watch for in Arizona include Leaf Miner and Aphid. The first line of defense is companion planting: Pea and Strawberry 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.
Spinach Garden Calendar for Arizona
| Month | Task | Notes |
|---|---|---|
| January | First harvest window opens | Spinach begins producing 40–50 days after transplant |
| February | — | Off-season |
| March | — | Off-season |
| April | — | Off-season |
| May ← | Watch for bolting | Harvest promptly; spring heat arrives quickly |
| June | — | Off-season |
| July | — | Off-season |
| August | — | Off-season |
| September | — | Off-season |
| October | — | Off-season |
| November | Fall crop planting | Transplant or direct sow for fall harvest before frost |
| December | Direct sow seeds | Sow seeds 1/4–1/2 inch deep, 6 inches apart |
Spinach Growing Tips for Arizona Gardeners
- •Direct sow in very cold soil — spinach germinates at 35°F, earlier than almost any other crop.
- •Succession plant every 10 days until 2 weeks before heat sets in for continuous spring harvests.
- •Arizona's cool-season spinach plants best in October, November, and December for winter and early spring harvest. Spring plantings bolt before producing a harvestable crop.
- •Switch to bolt-resistant varieties like Malabar or New Zealand spinach for summer heat (though technically different species).
Companion Planting for Spinach in Arizona
In Arizona's warm climate, planting spinach with Pea and Strawberry helps deter pests and improve soil. Avoid planting near Fennel, which inhibit spinach growth through root chemistry or shared pest pressure. See the full spinach companion planting guide for the complete list.
Spinach 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 spinach in Arizona?
In Arizona (Zone 9b), start spinach seeds indoors around Year-round and transplant outdoors around null — 0 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 spinach year-round in Arizona?
spinach is a cool-season crop in Arizona, with spring and fall windows. Summer heat bolts the plants before they can produce a harvestable crop. Succession planting every 2–3 weeks stretches the harvest window.
What spinach varieties grow best in Arizona?
For Arizona's Zone 9b, consult a local nursery or extension office for spinach variety recommendations.
When do I start spinach seeds indoors in Arizona?
Spinach does not need indoor starting in Arizona — direct sow around December 11–21 once soil reaches 35°F. Indoor starting is not recommended for this crop because spinach transplants poorly.