How to Grow Tomatoes in Arizona’s Low Desert

If you’ve been told tomatoes just don’t grow in the low desert, that’s not true. They grow well here. You have to work with our seasons instead of the ones on the back of the seed packet.

We get two seasons of tomatoes here, spring and fall, with a hot break in the middle where almost nothing sets fruit. Once you know that, the rest of it makes a lot more sense. I’ve grown tomatoes for years in my Mesa garden, through good springs, brutal summers, and mild winters that kept plants going into the next year. This is what works for me.

Why Tomatoes Produce in Spring and Fall Here

Tomatoes like warm weather, but they set fruit in a fairly narrow range. They need daytime temperatures in the 70s and 80s and nights in the 50s and 60s. Once days are consistently in the 90s and nights stay warm, the pollen turns sticky and stops working. The blossoms dry up and drop without setting fruit. Warm (and hot) nights are tough on plants. They don’t get a chance to recover.

That’s why we get good fruit set in spring, almost nothing in July and August, and another round in fall once the nights cool off. Heat affects ripening too. The red color develops best in the 70s, so when fruit gets very hot, it struggles to turn red and may develop yellow shoulders or ripen unevenly.

That’s why I plant in spring and fall. I get as much flowering and fruiting as I can in those two seasons, then keep the plants alive through the summer in between.

The Tomato Year in My Low Desert Garden

I think of tomatoes here in four phases: a spring planting and growing window, a summer where I’m keeping plants alive, a fall planting and growing window, and a winter where established plants hold on and give me a head start.

A year of tomatoes in my garden goes like this. I start seeds indoors in December or January so transplants are ready to go out in mid-February or March, once frost danger has passed, and the soil is at least 60 degrees. Those plants set most of their fruit before the worst heat. By June, I’m harvesting, but I’m already starting more seeds indoors for fall and trying to keep the spring plants alive through summer. To learn more about how to plant tomatoes, read this guide.

In August and September, I put out new transplants and prune and feed the spring plants that made it through to push a new flush of blooms. As it cools in late fall, I harvest what I can and bring some fruit indoors to finish ripening. During frost events, I cover plants so they make it through. The ones that survive already have a strong root system, and as soon as the days warm up, they often give me my earliest spring tomatoes.

Spring Is a Race Against the Heat

Spring tomatoes are a race. The earlier they set fruit, the more you get before the heat stops fruit set. So I plant as early as I can get away with, right after the last frost. If the weather’s warm, I’ll plant.

That’s a judgment call. Get a late freeze, and you might be planting twice. One spring, I planted tomatoes three times. The transplants from seeds I started indoors froze. Then I bought some specialty transplants I was excited about and lost those to a second late freeze. I finally tracked down more transplants, and those were the ones that took. Would I do it again? Probably. When your season is short, you have to gamble a little to get plants in early, even though you know a late freeze might cost you a round. With summer temperatures rising earlier than they used to, I’m adjusting many things in my garden, including when I plant tomatoes.

Choosing Varieties That Produce in the Low Desert

Variety choice makes a big difference Big beefsteak types are delicious, but with such a short season, you don’t always get a harvest before it’s too hot. Smaller-fruited types like cherry, grape, plum, and paste tomatoes are more reliable. They set earlier, handle heat better, and keep going when bigger types slow down.

A few things I look for. I want days to harvest around 70 from transplant, so the fruit has time before the heat sets in. I look for heat-set types like Jolene, bred to set fruit when it’s warmer than ideal. And because root-knot nematodes and soil diseases are real problems in our warm soil, I choose varieties with some resistance to diseases and nematodes when I can.

My go-to varieties are Jolene, Cherokee Purple, Early Girl, Black Krim, and Punta Banda, plus cherry and grape types like Sungold, Juliet, Sweet 100, and Yellow Pear. Learn more about what does well here in my post on the best tomato varieties for desert gardening.

Where You Plant Matters as Much as What You Plant

Tomatoes need sun, but they don’t want to bake against a west-facing wall or sit in a rock island soaking up reflected heat. Look for a spot with morning sun and some afternoon shade. Once temperatures are consistently above 90°F, I add white 50% shade cloth to protect blossoms and fruit from sunscald, and I take it back down when highs drop below 90°F again.

This spring, I had tomatoes in an elevated bed, and elevated beds heat up and dry out faster than beds on the ground. I had oyas in there to help, but I went out of town, the bed dried out unevenly, and I came back to blossom-end rot on most of the tomatoes. The stressed plants started attracting leaf-footed bugs, and I gave up and pulled the tomatoes for the season. Elevated beds can grow great tomatoes, but they’re harder to keep evenly watered. Learn more about how to garden in elevated beds, including tips for hot climates.

What Still Gives Me Trouble

A couple of things can still be challenging. Trellising is one. I always underestimate how big tomatoes get. The Garden in Minutes cages I like work great for compact determinate types, but a big, sprawling plant will outgrow them. A single Juliet can take up a whole four-foot trellis in my garden. Put your supports in at planting time, so you’re not forcing a big plant into a cage later and snapping branches.

Pruning is the other. In cooler, humid climates, people prune tomatoes hard to open the plant up. In our heat, I leave more of the plant on, because every leaf is shade for the fruit. I think of the leaves as a living umbrella over the tomatoes. I take off leaves touching the soil, remove dead or diseased branches, and keep some suckers pruned so the plant doesn’t get out of hand. But I leave enough to shade the fruit and prevent sunscald. It’s not a one-size-fits-all answer. For pruning after frost or winter damage, I have a separate post on pruning tomatoes, peppers, and eggplants.

Getting Through Summer and Into Fall

In the hottest part of summer, don’t expect much. Keep plants alive with shade and deep, even watering, and stop feeding them. They’re already stressed, and feeding pushes tender new growth they can’t support. Once fruit stops setting, the plants are holding on until cooler weather.

When temperatures start to drop, you have two choices. Give the surviving plants a light prune and a feeding to wake them back up, or pull them and replace them with fresh transplants. Some years, my spring plants look rough enough by fall that I replant. In other years, they bounce back and give me an early fall crop from an established root system. I decide plant by plant, based on how they look and whether the new growth is healthy. I walk through the process in my post on how to revive and prune over-summered tomatoes.

When You Get a Mild Winter, Lean Into It

Most years, I replant each season. But when we get a mild winter, I keep my plants going, and it pays off. This past year was mild; I kept the plants through it, and my freezer is full of tomatoes right now. When I get a large harvest, I love using extra tomatoes in my homemade garden salsa recipe.

Those plants didn’t look pretty. Tomatoes often carry damaged leaves and some disease on the lower branches by that point. I keep the bottoms pruned up and throw the diseased leaves in the trash, not the compost. But if the new growth is healthy and the plant is still setting fruit, I keep it going. If it’s still producing, it earns its space, ugly leaves and all.

Growing Tomatoes in Arizona FAQs