How to Grow Tomatoes in Arizona – 10 Tips for Growing Tomatoes

Learning how to grow tomatoes may feel overwhelming. Entire books have been written about growing tomatoes, but these 10 tips will fast-track you to tomato-growing success. 

The taste of homegrown tomatoes is the reason many people begin a garden. In the United States, it is said that more gardeners grow tomatoes than any other vegetable.

Wondering about how to grow tomatoes in Arizona, the low desert, and other hot climates? Keep reading; there is plenty of information for you too!

Low desert includes elevations below 3500 ft in the Southwest, such as the Phoenix and Tucson metro areas.

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10 Tips for How to Grow Tomatoes

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Tip #1 for Growing Tomatoes: Choose a tomato variety suited for your tastebuds and climate

Decide which type of tomato you want to eat. Different types of tomatoes are suited for eating fresh, canning, making salsa, or cooking. 

For the best chance of success, choose a type of tomato suited to your climate. 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: Punta Banda, Celebrity, Pearson, Speckled Roman*, Black Krim*, Atomic Grape*, Sungold, Sweet 100, Yellow Pear, Canestrino*, and Cherokee Purple.

(* Local Master Gardener Carol Stuttard recommended varieties.)

Florida gardeners battle high heat and humidity. The Everglades tomato does well in those conditions.

Different climates have other considerations and growing conditions. Ask a local grower for varieties that do well in your area.

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Tip #2 for How to Grow Tomatoes: Plant tomatoes at the correct time

To give tomato plants the best chance for success, plant tomatoes right after the last spring frost date. This is usually around February 15th – March for the low desert of Arizona. 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 planting tomatoes in Arizona’s low desert from July through September. For this planting, start seeds indoors from May – July. 

Once planted, protect plants from high daytime temperatures with a shade cloth. Plant tomatoes in the evening so tomatoes 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 not viable. Fruit that has set will continue to mature, but new fruit will not set if pollen is not viable. 

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Tip #3 for Growing Tomatoes: Plant tomatoes in the right location

• The most important requirement for productive tomatoes is plenty of sunshine.
• Give tomatoes full sun for the entire plant with adequate growing space around each plant for air circulation.
• Allow 2 feet between each plant for healthy and productive plants.
• Do not plant tomatoes in the same location year after year. Rotate the location to prevent build-up of disease in soil.  

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Tip #4 for How to Grow Tomatoes: Prepare soil correctly

Tomatoes need soil rich in organic matter; make a habit of amending your soil with compost. Good drainage is important as an area with standing or puddling water invites disease. Prepare your soil correctly and your plants will thank you. If you are growing tomatoes in raised beds, this article talks about the best soil for raised beds. 

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Tip #5 for Growing Tomatoes: Plant tomato seedlings deeply

Planting deeply encourages a more extensive root system and a healthier plant.

• Remove the bottom 2/3 of leaves on the tomato transplant.
• Dig a shallow trench or deep hole (depending on depth of planting bed) and plant transplant so that only top leaves are above the ground.
• Roots will grow along the entire stem of the plant.
• Bear in mind that plants may appear to do nothing for a bit after planting the tomato- but they are growing roots.

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Tip #6 for How to Grow Tomatoes: 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 helps control weeds, and plants will not have to compete with weeds for water and nutrients. Most mulch ultimately becomes fertilizer as it decomposes into the soil around the plant.

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Tip #7 for Growing Tomatoes: Water tomato plants correctly

• Water early in the day to prevent excessive evaporation.
• It’s best to water at the soil level, so leaves do not get wet. Wet leaves encourage disease.
• Water to a depth of at least 12 inches to encourage roots to grow deep in the soil to find nutrients and moisture. 
• Water slowly and deeply.
• Deep, extensive roots help plants withstand dry spells.
• Water regularly as needed, but do not allow plants to become soggy as plant roots need oxygen. How often you water depends on your soil and the weather conditions. Water deeply each time you water and then let the top few inches dry out before watering again. During the hottest months of the summer, that might mean every day. During the winter, that often means every 7-10 days.

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Tip #8 for How to Grow Tomatoes: Feed tomato plants

When planting, if your soil is low in phosphorus 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 is phosphorus. Without proper fertilization, plants do not produce well and are prone to weeds (which invite pests and other diseases).

Once tomatoes set fruit feed them about once a month. Tomatoes do best with regular feeding from organic sources of fertilizer. I feed mine with a diluted fish emulsion/seaweed fertilizer.

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Tip #9 for Growing Tomatoes: Provide support for growing tomato plants

It’s important to encourage tomatoes to grow vertically.

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

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Tip #10 for Growing Tomatoes: Provide shade for tomato plants in extreme climates like Arizona

Your plants may need a little help to get through a long, hot summer in the low desert of Arizona.

•  Shade can reduce the air temperature for tomatoes by several degrees, and it also extends the growing season.
• Providing shade in desert climates helps reduce stress on tomato plants, and can prevent sunscald on ripening tomatoes.
• Shaded tomato plants are more likely to survive the extreme heat of the desert, and may perform better when cooler temperatures return in the fall.

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