How to Grow Tomatoes in Arizona: 10 Tips for Success

Learning how to grow tomatoes in Arizona can feel a bit overwhelming, especially with all the advice out there. Arizona’s short growing seasons can make growing tomatoes challenging but not impossible. Planting time and variety selection are crucial for success. If you’re wondering how to grow tomatoes in Arizona’s low desert or other hot climates, you’re in the right place. Let’s get started!

Article Index:

1. Select a tomato variety suited to your climate
2. Plant tomatoes at the correct time
3. Choose the best location for tomatoes
4. Prepare soil correctly
5. Plant tomato seedlings deeply
6. Mulch tomato plants well
7. Water tomato plants correctly
8. Fertilizing guidelines
9. Provide support for growing tomato plants
10. Extreme heat tips for tomatoes

1. Select a tomato variety suited to your climate

Choose a tomato type suited to your climate for the best chance of success. Because of the heat of Arizona summers, we have a short growing season. Look for plants with short (60-90) days to maturity. These are often types with small to medium fruit or Roma or paste varieties.

Varieties highly recommended for desert climates like Arizona include Celebrity, Sungold, Sweet 100, Yellow Pear, and Cherokee Purple. (Click the names for seed sources.) This blog post outlines more of my favorite varieties for Arizona.

Florida gardeners battle high heat and humidity. The Everglades tomato does well in those conditions. Other climates have different considerations and growing conditions. Ask a local grower for varieties that do well in your area.

2. Plant tomatoes at the correct time

To give tomato plants the best chance for success, plant tomatoes right after the last spring frost date. For the low desert of Arizona, this is usually around February 15th – March. For this planting, start seeds indoors from December—January. 

Once planted, if necessary, protect plants from cold nighttime temperatures. Plant tomatoes in the morning so tomatoes have the day to settle in before cooler nighttime temperatures. 

There is a second (monsoon) planting window for tomatoes in Arizona’s low desert from July through September. For this planting, start seeds indoors from May through July. Once planted, protect plants from high daytime temperatures with shade cloth. Plant tomatoes in the evening so they have a cooler evening to settle in before hot daytime temperatures. 

Tomatoes grow best in temperatures of 70℉ to 90℉, with nighttime temperatures consistently above 55℉. In Arizona, you want tomatoes to flower and set fruit before it gets too hot. Once temperatures reach 90℉, tomato pollen is often not viable. Fruit that has been set will continue to mature, but new fruit will not be set if pollen is not viable. 

3. Choose the best location for tomatoes

Tomatoes thrive with lots of sunlight, so plant them in an area with at least 6-8 hours of sun. Give each plant enough space—about 2 feet apart—for good air circulation and healthy growth. It’s also important to rotate where you plant tomatoes each year to avoid soil diseases from building up.

4. Prepare soil correctly

If your soil is low in phosphorus when planting, it’s important to provide a source of phosphorus (bone meal or rock phosphorus) and again as plants begin to bloom and produce fruit. A soil test can determine if your soil is low in phosphorus. Without proper fertilization, plants do not produce well and are prone to weeds (which invite pests and other diseases).

Tomatoes need soil rich in organic matter; make a habit of amending your soil with compost and worm castings. Good drainage is important as an area with standing or puddling water invites disease. Prepare your soil correctly, and your plants will thank you.

5. Plant tomato seedlings deeply

Planting your tomatoes deeply helps develop a stronger root system, resulting in a healthier plant. Start by removing the bottom two-thirds of the leaves from the tomato transplant. Then, dig a shallow trench or a deep hole, depending on the depth of your planting bed. Place the transplant in the trench or hole, leaving only the top leaves above the soil. This method encourages roots to grow along the entire buried stem.

Remember that it may seem like your tomatoes aren’t growing after planting, but they’re busy developing a robust root system beneath the soil.

6. Mulch tomato plants well

Use compost, straw, leaves, or pine needles to reduce evaporation and insulate the soil from extreme hot and cold temperatures; soil will stay at a more even temperature. Mulching is especially critical when growing tomatoes in hot climates like Arizona’s low desert.

Mulching helps control weeds, and plants will not have to compete with weeds for water and nutrients. Most mulch becomes fertilizer as it decomposes into the soil around the plant. Learn more about how to mulch in this post.

7. Water tomato plants correctly

Proper watering is key to tomato health. Start by watering early in the day to minimize evaporation. Aim to water at the soil level, keeping the leaves dry to avoid diseases that thrive on wet foliage.

Make sure to water deeply, at least 12 inches down, to encourage the roots to grow deep in search of nutrients and moisture. Deep, slow watering helps plants develop strong root systems that can better withstand dry spells.

Water regularly, but avoid overwatering—roots need oxygen, too, so the soil shouldn’t be soggy. The frequency of watering depends on your soil and the weather. You may need to water daily during the hottest months, but once every 7-10 days in winter is usually enough. Always water deeply and let the top few inches of soil dry out before the next watering.

8. Fertilizing guidelines when growing tomatoes in Arizona

When growing tomatoes in Arizona, it’s important to give them a little extra care once they start setting fruit. Feeding your tomatoes with organic fertilizer about once a month throughout the growing season will help them thrive and produce their best. Use organic sources like compost, worm castings, or other organic fertilizer.

However, it’s best to hold off on fertilizing when temperatures soar in the summer, as it can stress the plants. Wait until the weather cools down and you see new growth before resuming fertilization.

9. Provide support for growing tomato plants

Growing tomatoes vertically keeps the plant upright, preventing stems from breaking from heavy fruit or wind. Trellising tomatoes also keeps the leaves off the ground, which helps reduce diseases. Fruit is also easier to harvest when it is off the ground. 

10. Extreme heat tips for growing tomatoes in Arizona

If you’re growing tomatoes in Arizona, your tomato plants might need extra help to survive the long, hot summer. Providing shade can lower the air temperature around your plants by several degrees, helping to extend their growing season and prevent sunscald on ripening tomatoes. Shading also reduces stress, making your tomatoes more likely to survive the extreme heat and thrive again when cooler weather returns in the fall.

However, you may find better success by planting new tomatoes each fall rather than trying to keep them going through the summer. The intense heat is brutal on plants, making them more vulnerable to diseases. Stressed plants can also attract pests, which can spread to the rest of your garden. Starting fresh each season with new plants can help keep your garden healthy and productive.

Want more information about gardening in Arizona? This blog post shares 7 tips for  how to grow a vegetable garden in Arizona. 

More Tomato Growing Resources on My Blog:

• How to Plant Tomatoes: A Step-by-Step Guide
• Prevent Blossom End Rot: Tips for Healthy Tomatoes
• Turning Green Tomatoes Red: 4 Ways to Ripen Green Tomatoes
• Tomatoes for the Desert: Best Varieties for Arizona

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