When To Plant Tomatoes In Arizona

Figuring out when to plant tomatoes in Arizona is the first step to a successful harvest. Our unique desert climate means timing is everything, and getting it wrong can lead to scorched plants or stunted growth. This guide will walk you through the ideal planting schedule for every region of the state, from the low deserts to the high country.

You’ll learn how to work with our two main growing seasons, choose the right varieties, and protect your plants from extreme heat. Let’s get your tomato garden started on the right foot.

Unlike most of the country, Arizona offers two distinct tomato planting windows. The key is avoiding our intense summer heat, which can cause blossoms to drop and prevent fruit from setting. Your schedule depends entirely on where you live.

Understanding Arizona’s Growing Seasons

Arizona has a primary growing season in the cool months and a second, shorter one in the late summer. Tomatoes are warm-season crops, but they have their limits. Daytime temperatures consistently above 90°F and nighttime temps above 75°F will cause problems.

Fall Planting (Main Season): This is the most productive and popular time. You plant in late summer to early fall so plants mature during the pleasant autumn and winter months.
Spring Planting (Second Season): You plant in late winter to very early spring, aiming for fruit to set before the summer furnace kicks in.

Planting Schedule by Arizona Region

Here’s a breakdown of the ideal timing for different elevations. These dates are guidelines; always watch your local weather for early heatwaves or unexpected frosts.

Low Desert (Phoenix, Tucson, Yuma, Casa Grande)

Fall Planting: Start seeds indoors in early to mid-July. Transplant seedlings into the garden from late August through September 15th. Planting any later risks the plants not maturing before frost.
Spring Planting: Start seeds indoors in December or January. Transplant outdoors from mid-February to mid-March. Use heat-tolerant varieties and be prepared to provide afternoon shade by May.

Intermediate/High Desert (Prescott, Sierra Vista, Globe)

Fall Planting: Start seeds indoors in mid-June. Transplant outdoors from late July to early August. The slightly cooler summers allow for an earlier start.
Spring Planting: Start seeds indoors in February. Transplant outdoors after the last frost date, typically from April to early May. You have a longer spring window before summer heat arrives.

Mountain Regions (Flagstaff, Payson, Show Low)

These areas have one clear growing season due to the threat of frost. The short, cool summers are perfect for tomatoes if you time it right.

Spring/Summer Planting: Start seeds indoors 6-8 weeks before your last expected frost (often in late May or June). Transplant seedlings outdoors only after all danger of frost has passed and soil has warmed, usually from early June to early July. Use short-season or cold-tolerant varieties.

Choosing the Right Tomato Varieties for Arizona

Variety selection is crucial. For the fall season, you need tomatoes that set fruit in warm soil but can handle cooler nights as they mature. For spring, heat-tolerance is paramount.

For Fall Planting: Look for varieties with shorter “days to maturity” (less than 75 days). Good choices include ‘Early Girl’, ‘Celebrity’, ‘Champion’, and ‘Sweet 100’ cherry tomatoes.
For Spring Planting: Choose heat-set varieties like ‘Heatmaster’, ‘Solar Fire’, ‘Phoenix’, or ‘Sunmaster’. These are bred to produce pollen even in high temperatures.
Determinate vs. Indeterminate: Determinate (bush) tomatoes produce fruit all at once and are great for canning. Indeterminate (vining) tomatoes produce all season long. In Arizona’s long seasons, indeterminate types often yeild more.

Step-by-Step Planting and Care Guide

Once you have your timing and varieties sorted, follow these steps for healthy plants.

1. Soil Preparation

Arizona native soil is often alkaline and clay-heavy. Tomatoes need rich, well-draining soil.

Amend your planting area with 3-4 inches of quality compost or well-rotted manure.
Consider planting in raised beds filled with a garden soil mix for better drainage and root development.
A soil pH between 6.2 and 6.8 is ideal. You may need to add sulfur to lower pH if your soil is very alkaline.

2. Planting Your Tomatoes

Plant in the evening or on a cloudy day to reduce transplant shock.
Dig a hole deep enough to bury 2/3 of the tomato stem. Tomatoes can develop roots all along their buried stems, creating a stronger plant.
Remove the lower leaves and place the plant in the hole. Fill with soil and water deeply.
Space plants 24-36 inches apart to ensure good air circulation.

3. Watering and Mulching

Consistent watering prevents blossom end rot, a common issue here.

Water deeply and infrequently to encourage deep roots. Aim for 1-2 inches per week, adjusting for temperature.
Use drip irrigation or soaker hoses to keep water off the leaves and prevent disease.
Apply a 3-4 inch layer of organic mulch (straw, wood chips) immediately after planting. This keeps soil cool, retains moisture, and supresses weeds.

4. Fertilizing

Tomatoes are heavy feeders. Use a balanced fertilizer at planting time. Once flowers appear, switch to a fertilizer lower in nitrogen and higher in phosphorus to promote fruiting. Follow package instructions carefully to avoid over-feeding.

Protecting Tomatoes from Arizona Extremes

Your main challenges will be intense sun, heat, and occasional frost.

Heat Protection

For spring-planted tomatoes, use 30-50% shade cloth installed above the plants by early May. This can lower temperatures significantly.
Ensure consistent watering. Stressed plants are more suseptible to sunscald on the fruit.
Never prune off all leaves; the fruit needs some foliage to prevent direct sunburn.

Frost Protection

In the low desert, a light frost can occur in December or January.

Cover fall-planted tomatoes with frost cloth or old bedsheets on cold nights. Secure it to the ground to trap heat.
For potted plants, move them against a south-facing wall or into a garage overnight.

Common Arizona Tomato Problems & Solutions

Blossom Drop: Caused by temperatures too high (above 90°F daytime) or too low (below 55°F nighttime). The solution is planting in the correct season and using heat-tolerant varieties.
Blossom End Rot: A dark, leathery spot on the bottom of the fruit. It’s caused by calcium deficiency often due to irregular watering. Maintain consistent soil moisture and avoid over-fertilizing with nitrogen.
Whiteflies: A major pest in Arizona. Use yellow sticky traps, spray with a strong stream of water, or apply insecticidal soap. Encourage beneficial insects like ladybugs.

FAQ: Planting Tomatoes in Arizona

Can I grow tomatoes in Arizona summer?

It is very challenging. The extreme heat usually causes blossom drop, preventing fruit set. If you try, use heat-set varieties, provide afternoon shade, and be prepared for lower yields.

What is the latest I can plant tomatoes in the fall in Phoenix?

Aim to have transplants in the ground by September 15th. Planting later gives the plant to little time to establish and produce before the risk of frost in December.

Should I start from seeds or buy transplants?

Starting from seed gives you access to many more variety options, which is crucial for finding Arizona-adapted types. However, buying transplants from a local nursery in the correct season is a great and easier option for beginners.

How often should I water my tomato plants?

There’s no single answer. In peak summer heat, you might water every other day. In the cool winter, once a week may suffice. Always check soil moisture 2-3 inches down; water when it feels dry.

Why are my tomato plants flowering but not producing fruit?

This is almost always a temperature issue. If it’s too hot, the pollen becomes sterile. If it’s too cool, pollination doesn’t happen. Ensure you are within the ideal planting window for your region.

By following Arizona’s ideal planting schedule and choosing the right care tactics, you can enjoy a bountiful tomato harvest. Pay close attention to your local climate micro-climate, and don’t be afraid to adjust based on the weather each year. With good timing and a little desert gardening know-how, you’ll be picking homegrown tomatoes for many months.