Plant tomatoes in Arizona in late February through March for spring harvest, or in late July through August for fall harvest
Arizona's two growing seasons flip the calendar most gardeners follow. Tomatoes need warm soil and air to thrive, but Arizona's brutal summer heat kills them. Instead, you plant in late winter so they mature in spring, then again in midsummer so they fruit in fall and early winter when temperatures drop back to survivable levels.
The exact dates depend on your location within Arizona. Phoenix and the low desert (below 2,000 feet elevation) have a longer warm season than Flagstaff or Prescott. Soil temperature matters more than air temperature—tomatoes won't germinate or grow in cold soil, even if days are warm. Most Arizona gardeners wait until soil reaches 60°F before planting, which usually happens by late February in the low desert.
Key Takeaways
- Spring planting in Arizona runs from late February through March in the low desert, with transplants ready to go in the ground when soil hits 60°F.
- Fall planting happens in late July through August so tomatoes mature during Arizona's mild autumn instead of the deadly summer heat.
- Soil temperature, not air temperature, determines when seeds will sprout and seedlings will grow—a soil thermometer costs under $10 and removes the guesswork.
- High-elevation areas like Flagstaff have a shorter window and may only support spring planting, while the low desert near Phoenix supports both seasons reliably.
- Transplants (seedlings started indoors or bought from a nursery) are faster and more reliable than direct seeding in Arizona's extreme climate.
Spring planting: late February through March in the low desert
In Phoenix and surrounding low-desert areas, late February is when soil warms enough for tomato seeds to germinate. If you are starting from seed indoors, begin 6 to 8 weeks before that date—around early January. Seedlings will be ready to transplant outdoors by late February or early March when they have their first true leaves and soil has warmed.
If you are buying transplants from a nursery, wait until late February or early March to plant them outside. Nurseries in Arizona time their stock to this window, so you will find healthy seedlings available then. Plant them in full sun (at least 6 hours daily, ideally 8 or more) and water deeply after planting.
Spring tomatoes in Arizona typically flower by April and May, then produce fruit through May and June before the heat becomes unbearable. By mid-June, most varieties stop setting fruit and the plants decline. This is normal and expected—you are not fighting the climate, you are working with it.
Fall planting: late July through August for autumn and winter harvest
The fall crop is often more reliable than spring in Arizona because the weather is more predictable and pests are fewer. Start seeds indoors in late May or early June so transplants are ready by late July. Alternatively, buy transplants in late July or August from nurseries that stock them for fall planting.
Plant transplants in late July through August. They will grow slowly through the remaining heat, then accelerate in September and October as temperatures drop. Flowering begins in September and October, with fruit ripening from October through December and into January in mild years.
Fall tomatoes often produce more fruit per plant than spring crops because they mature during cooler, more stable weather. They also face fewer pests and diseases. The main challenge is keeping them watered during the August heat while they are still establishing roots.
How to check soil temperature without guessing
A soil thermometer removes the guesswork and costs $8 to $15. Push it 3 to 4 inches into the soil in the morning, wait 2 minutes, and read the temperature. Tomatoes germinate best when soil is 70°F to 80°F, but will grow (slowly) at 60°F. Most Arizona gardeners aim for 65°F or higher to be safe.
Check soil temperature in the spot where you plan to plant, not just anywhere in your yard. A sunny bed warms faster than a shaded one. If you are planting in containers, the soil in pots warms faster than ground soil, so you can often plant a week or two earlier in containers.
Differences between low desert, high desert, and mountain elevations
Phoenix and the low desert (Tucson, Yuma, areas below 2,000 feet) have two solid growing seasons. Spring planting works from late February onward, and fall planting works from late July onward. Both seasons are reliable.
The high desert (areas around 3,000 to 4,000 feet, including parts of the Scottsdale foothills and some areas east of Phoenix) has a shorter window. Spring planting still works in March, but fall planting becomes risky because frost arrives by November, cutting the season short. You may get only one crop per year.
Mountain areas (Flagstaff, Prescott, above 4,000 feet) have a single short season in late spring and early summer. Plant in April or May after frost danger passes, and expect harvest by August or September before fall frost returns. Fall planting does not work in these areas.
Why transplants usually work better than direct seeding in Arizona
Direct seeding (planting seeds straight in the ground) works in other climates but is risky in Arizona. Seeds need consistent moisture and moderate temperatures to germinate. Arizona's spring sun is intense, and soil dries quickly. Seeds can bake before they sprout, or seedlings can wilt in the heat.
Starting seeds indoors or buying transplants from a nursery gives you a head start. Transplants are already established and can handle the transition to outdoor sun and heat better than fragile seedlings. In Arizona, transplants are the standard approach for a reason.
If you do direct seed, plant in a shaded spot or use shade cloth to keep soil cooler and moister during germination. Water daily. This adds complexity, so most Arizona gardeners skip it and use transplants instead.
Preparing soil and containers before planting day
Tomatoes are heavy feeders and need rich soil. Mix compost or aged manure into garden beds before planting—aim for 2 to 3 inches worked into the top 8 to 10 inches of soil. If you are planting in containers, use a quality potting mix (not garden soil), not plain dirt from your yard.
Container size matters. Determinate varieties (bush types) need at least 5 gallons per plant. Indeterminate varieties (vining types that grow all season) need 10 gallons or more. Larger containers hold moisture longer and reduce watering frequency, which is critical in Arizona heat.
Set up drip irrigation or soaker hoses before planting if possible. Arizona's heat means daily watering is often necessary, and hand-watering is time-consuming and inconsistent. Drip systems deliver water slowly to the root zone and reduce waste.
Frequently Asked Questions
Can I plant tomatoes in January in Arizona?
Not outdoors in the low desert. Soil is too cold in January—it typically sits around 50°F or lower. You can start seeds indoors in January for transplanting in late February, but planting transplants or seeds directly outside will result in rot or no germination. Wait until late February when soil warms.
What happens if I plant tomatoes too early in spring?
Cold soil slows or stops germination. Transplants planted in cold soil sit dormant and may rot before roots establish. You lose weeks of growth. It is better to wait two weeks and plant in warm soil than to plant early and watch nothing happen.
Is the fall crop really better than spring in Arizona?
Often yes. Fall tomatoes mature during cooler, more stable weather, so they produce more fruit and fewer problems with pests and disease. Spring crops race against the heat and often stop producing by early summer. Fall crops can produce through December in mild years, giving you a longer harvest window.
Can I grow tomatoes year-round in Arizona?
No. Winter (December through February) is too cold for growth, even in the low desert. Summer (June through August) is too hot. You get two windows: spring (February to June) and fall (July to December). Between them, the plant either freezes or cooks.
Do I need shade cloth for spring tomatoes in Arizona?
Not usually in spring. Spring sun is intense but not yet lethal. By late May and June, 30% shade cloth can extend the season slightly by keeping plants cooler, but most gardeners accept that spring production ends as heat rises. Fall tomatoes rarely need shade because temperatures are already dropping.