August Gardening Tasks for Low Desert Arizona Garden

Coming off July is tough. It’s hot, you don’t want to be outside, and it takes real work to keep things alive during an Arizona summer. The garden I see in the afternoon and the garden I see in the morning are two different gardens. In the afternoon, plants are wilted and struggling to survive. But in the morning, especially with a little monsoon moisture, the same plants usually look pretty good. We got rain this year, and mine are holding up better than the afternoons suggest.

August is the time to roll up your sleeves and get to work getting things back in shape, so you’re ready for our peak growing season of fall. Pruning peppers and tomatoes, amending beds, and making sure you’re ready to go when the fall season begins are a big part of what we do in the Arizona garden in August.

August in the Low Desert at a Glance

If you only have an hour in the garden this month, spend it on these:

• Check your irrigation. Run the system and walk every line, looking for clogged emitters and leaks.
• Water deeply, and go twice as deep once this month to flush salts out of the root zone.
• Add compost and worm castings to beds you’ll plant in fall. Organic matter breaks down fast in our heat and has to be replaced.
• Start cutting tomatoes back a third at a time, above new growth, and feed as you go. Don’t take an all or nothing approach.
• Order fall seeds, garlic, and bulbs before they sell out.
• Pull weeds after monsoon rain, before they set seed.

Prefer to watch? I walk through the whole August list in this video.

Looking for what to plant right now? This page covers August tasks and maintenance. For sowing dates and harvest timing, see what to plant and harvest in August in the low desert of Arizona, which walks through every crop that can go in the ground this month. Low desert means elevations below 3,500 feet in the Southwest, including the Phoenix and Tucson metro areas.

How Often Should I Water My Arizona Garden in August?

Check plants in the morning. Afternoon wilt usually means the plant is losing water faster than the roots can pull it up. That happens even when the soil is wet. If the plant has perked back up by morning, your watering is fine. If it’s still wilted in the morning, you have a watering problem. Adding more water to a plant that was only wilting from afternoon heat can waterlog the roots.

Raised beds and annual vegetables: water to a depth of 8 to 12 inches every 2 to 3 days, letting the top of the soil dry between waterings. I water my raised beds every 2 to 3 days in August. I use the garden grids from Garden in Minutes to water my raised beds. Use code Angela10 to save $10 off $100, or ANGELA to save 7% on any size order.

Containers: check daily. You may need to water every day. I water my containers every 2 to 3 days and fill the ollas each time. If you’re not sure, use a moisture meter to check.

Use a soil probe to check depth. Aim for 3 feet on trees, 2 feet on landscape plants, and 1 foot on annuals. Watering the surface every day keeps roots shallow, in the hottest part of the soil.

Flush salts once this month. Water twice as deep as usual in one session. Summer heat and dry soil concentrate salts, and local water supplies get saltier later in the summer. A single deep watering moves them below the root zone.

I notice salt burn the most in my citrus. If you can go out with a hose on a small drip and let it really soak in, that will help your citrus get through the summer. Slow is the important part. Water applied fast runs off or channels straight down without carrying the salts with it.

Check the irrigation system now if you haven’t. Run it while you watch. Look for clogged emitters, cracked lines, and heads spraying the wrong direction. Timers and irrigation supplies fail in the heat, and most people don’t notice until a plant is gone.

Tree and Vine Watering in August

Watch fruit trees for water stress. Leaf curling is the first sign you’ll notice. Wet the soil from the trunk to just past the drip line, and expand basins around trees to extend a foot beyond the drip line as needed.

• Established citrus: every 7 to 14 days, to a depth of 2 to 3 feet
• Established fruit trees: every 7 to 10 days, to a depth of 18 to 24 inches
• Grape vines: deep watering every 5 days
• Annual fruit and high water use vines: every 2 to 5 days, to a depth of 8 to 12 inches
• Desert-adapted trees, shrubs, and vines: every 7 to 21 days (24 to 36 inches for trees, 18 to 24 inches for shrubs, 8 to 12 inches for vines)
• High water use trees: every 7 to 10 days, to a depth of 18 to 24 inches
• High water use shrubs: every 5 to 7 days, to a depth of 8 to 12 inches

Why Is My Fruit Splitting?

Splitting is a watering problem. Tomatoes, pomegranates, and citrus all do it. Fruit splits when the soil dries out. It also splits when dry soil suddenly gets soaked and the fruit takes up water faster than the skin can stretch. A monsoon storm after a dry stretch will do it. Remove split fruit so it doesn’t attract pests.

What Does Monsoon Season Change in the August Garden?

• Skip a watering after a good soaking. If you get half an inch of rain, you can probably skip one watering cycle. Check with a soil probe first. A short, hard storm often wets the surface and very little below it.
• Humidity brings different pests. Whiteflies and fungal problems pick up during monsoon, and spider mites come back once the humidity drops again.
• Weeds come up fast after rain. Pull them before they set seed.
• Check for storm damage. If a limb breaks, prune back to a main branch and make a clean cut. Clean cuts heal better.
• Catch the rain if you can. Rainwater harvesting, swales, and berms help you direct storm water where you want it. I use the harvested rainwater around the garden.
• Some summer crops keep producing. With the monsoon moisture this year, my asparagus beans, Armenian cucumbers, and watermelon are still flowering and producing. Plants that would normally be finished keep going when the humidity comes up. Look at the plant before you pull it.

How Do I Prepare Garden Beds for Fall Planting?

• Add compost, worm castings, spent cover crops, and other organic matter. Organic matter decomposes quickly in our heat and needs replenishing every season. Soil is a living thing you feed, not a bank account you draw down.
• Plant a cover crop if you’re not planting until September or October. Buckwheat and cowpeas both hold up to August heat and keep bare soil covered. More on growing heat-tolerant cover crops here.
• Cut back cover crops 2 to 3 weeks before planting. Cut at soil level and leave the tops on the soil, or cover them with compost. Leaving the roots in place keeps the soil structure intact.

If you want the full picture of how desert soil, timing, and watering fit together, my guide on growing vegetables in a hot, dry climate covers the principles behind these tasks.

Should I Cut Back Tomatoes and Peppers in August?

Yes, but you don’t need to take an all-or-nothing approach.

Tomatoes: If you have a variety you like, prune it back a third at a time over the next few weeks, cutting where you see new growth. A plant might have three main branches. Cut one back above new growth, wait a week, then do the next one. That’s much easier on the plant than taking it all down in one afternoon.

Feed while you’re doing it. Compost, worm castings, Nutrient+, and some AgroThrive over the next few weeks can make a big difference. Nutrient+ is what I use for supporting transplants and stressed plants, and a cut-back tomato in August qualifies. For timing on the liquid feeds, see how and when to use liquid organic fertilizer. Then see how it does.

Peppers and eggplants: They tolerate a hard cut back better than tomatoes do. If you see vigorous new growth, you’re usually fine to cut them back in one pass. If you’re worried about a particular plant recovering, take the slower approach with it too.

If your plants are really struggling or diseased, it’s fine to replant instead. Not every plant is worth nursing into fall.

Other vegetable garden tasks this month:

• Remove spent summer heat-loving vegetables and anything past its prime. A struggling plant is a pest magnet.
• Clear debris around plants to discourage pests looking for shelter.
• Remove spent artichoke heads and save the seeds.
• Harvest any remaining I’itoi onions.
• Pot up indoor-grown seedlings that have outgrown their containers if it’s not time to plant them out yet.
• Fertilize indoor-grown seedlings every other watering.

How Do I Plan a Fall Garden in August?

• Buy garlic if you want to grow garlic. Store it in the fridge until October planting.
• Buy organic potatoes and start chitting them if you’re planting potatoes next month. How to chit potatoes here.
• Order fall-planted bulbs like ranunculus and anemones. Store the corms in a cool closet until planting time. Grow guides for ranunculus, tulips, and anemones.
• Decide what actually matters to you. Nobody has room to grow everything. I plan around what I most want to walk outside and pick, then fill in around it with vegetables, herbs, flowers, and fruit.
• Use the Arizona vegetable planting calendar for the low desert to line up seed-starting and transplant dates. Timing is what separates a good desert fall garden from a frustrating one. For month-by-month tasks and succession planning in one place, the Low Desert Garden Planner is available in my shop.

What Pests Should I Watch For in an August Arizona Garden?

The best defense against pests is a healthy plant, which is hard in August because heat itself is the stressor. Walk the garden daily if you can. Problems caught small stay small.

• Whiteflies thrive in August conditions. They come off the underside of leaves like a small cloud when the plant is disturbed. Spray the undersides of leaves daily with 1 tablespoon of Dawn per gallon of water to keep numbers down.
• Spider mites are common this month. Treatment options here.
• Grasshoppers feed on new growth. Handpick, and hope the birds help.
• Squash bugs. Prevention and treatment here.
• Bagrada bugs, tomato hornworms, three-lined potato bugs, and leaf-footed bugs are all common now. Hand-pick every stage and drop them in soapy water.
• Corn borer larvae leave skeletonized patches on corn leaves. Treat with Bt or a drop of mineral oil on each tassel.
• Chrysanthemum lace bugs on sunflowers. What to do about black bugs on sunflowers.
• Leaf miners on cantaloupe and other melons. Remove the damaged leaves.
• Rollie-pollies eating seedlings, especially beans. Sprinkle a small amount of slug and snail bait at planting. More on keeping pill bugs out of the garden.
• Leaf-footed bugs on pomegranate trees. Watch for them now.

Leave these alone:

• Milkweed and other seed bugs on seed pods. They rarely cause real damage.
• Cicadas. The buzzing is constant and the exoskeletons turn up everywhere, but damage is minimal and the season ends on its own.
• Bird damage on melon and sunflower leaves. The leaves look chewed, the plant usually survives. Put out a bird bath instead. They’re thirsty.

Beneficial insects and wildlife you’ll see this month: lovebirds and finches on sunflowers, bees, assassin bugs, wasps, hummingbirds, praying mantids, lizards, and butterflies including swallowtails and gulf fritillary.

What Should I Do With Containers in August?

Containers heat up faster than the ground and dry out faster than anything else in the garden.

• Move containers to spots with natural afternoon shade. Morning sun and afternoon shade beats full sun for almost everything in August.
• Group containers and grow bags close together. They insulate each other and slow moisture loss.
• Refresh large containers with additional raised bed mix before fall planting. This is my preferred soil mix for raised beds and containers.
• Leave the small containers put away another month. Small pots hold too little soil to buffer August heat, and they dry out faster than you can keep up with.
• Watch for hydrophobic soil. If a container dries out completely, water runs off the surface instead of soaking in. Water slowly and check that it’s actually absorbing.
• Add ollas. They help enormously with summer container watering. I use ollas from Growoya and refill them every time I water.

Elevated beds solve a lot of the container problems at once. How to grow in elevated garden beds and elevated garden bed tips for hot climates cover what works here.

August Flower Garden Tasks

August isn’t a flower planting month in the low desert. The warm-season flowers are already in, and it’s too hot for the cool-season ones. Waiting until September gives you far better results. This month is maintenance and planning.

• Deadhead summer bloomers like zinnia, vinca, cosmos, and gaillardia to keep blooms coming.
• Don’t cut anything back hard. A severe cut in August usually doesn’t recover.
• Fertilize container-grown flowers this month.
• Save seeds from summer flowers including sunflowers, marigolds, tithonia, zinnias, and four o’clocks. Learn how to save seeds.
• Plan the fall wildflower garden. How to grow wildflowers.
• Don’t pull spent sunflowers. Cut them off just above soil level. The roots decay in place instead of tearing out a large ball of soil and everything growing near it. If you used sunflowers for shade this summer, this post covers how to time their removal.

The Arizona annual flowers planting calendar shows when to plant flowers in Arizona and when to start seeds indoors.

How Do I Care for Roses in August in Arizona?

Roses look rough in August. That’s normal and mostly survivable.

• Remove blooms right away on stressed plants. Blooming costs the plant energy it doesn’t have.
• Keep roses lightly deadheaded. I cut just under the bloom, nothing more.
• Don’t fertilize and don’t prune this month.
• Expect chlorosis. Yellowing between the veins is common now because roots can’t take up nutrients well in hot soil. It usually corrects itself as the soil cools.
• Evaluate placement. If a rose is severely burned, note it now and plan to move it in fall rather than trying to fix it in August.

Fall is rose planting season, and variety choice matters more here than almost anywhere. Memorial Day, Iceberg, Mother of Pearl, and Julia Child all handle low desert heat well.

I get all of my roses from Heirloom Roses. They’re own-root roses with no grafts, and they meet high standards for disease resistance. Use code GARDENAZ26 for 20% off roses, perennials, and bulbs. You can order now and have them shipped when you’re ready to plant, up to 8 months later.

August Fruit and Fruit Tree Tasks

• Keep fruit picked, and clean up what falls. Rotten, split, and sun-damaged fruit on the ground draws pests fast.
• Don’t prune this month. Pruning exposes bark that has been shaded all season, and it sunburns quickly in August.
• Apply the last round of citrus fertilizer between August and September. Water well the day before, and again after.
• Lemons and key limes start ripening. Harvest as needed. They keep ripening over the next several months, and flavor is best right after picking. Lemons hold in the fridge a couple of weeks, though I leave mine on the tree until I need them. Citrus growing tips for Arizona.
• Expand basins around trees to extend a foot past the drip line as needed.
• Root strawberry runners to make new plants for fall.

August Herb Garden Tasks

• Perennial herbs look spent right now. Keep harvesting as needed, but wait until September to give them a real trim and decide whether to replant. Cutting hard in August stresses a plant already at its limit. Perennial herbs for hot summer climates.
• Harvest basil often. Regular cutting encourages new growth and delays flowering and seed set. How to grow basil. When you have more than you can use, garden fresh tomato and basil pasta uses a lot of it at once.

The Arizona herb planting guide shows when to plant over 30 herbs here and whether to start from seed or transplant.

August Landscape Plant Tasks

• Plant hardy desert trees and cacti now. Warm soil is when their roots establish best. Best trees for low desert Arizona and native landscape plants for Arizona and the desert Southwest both help with selection.
• Wait on shrubs and perennials. Too hot. They establish far better planted in fall.
• Deadhead and lightly prune summer flowering plants like oleander, bird of paradise, Texas sage, and lantana to encourage more blooms.
• Leaning cactus means a root problem, usually from too much or too little water. Plants can fall. If a saguaro over 8 feet tall is leaning, call a professional.
• Don’t top trees. It damages the tree permanently. Thinning limbs to open the canopy is fine.
• Prune broken limbs properly after storms. Cut back to a main branch, clean cut.
• Evaluate struggling plants and make a fall plan. The usual causes are not enough water, too much sun or too much shade, or a plant that was never suited to a desert climate. Full sun or afternoon shade for Arizona landscape plants helps diagnose sun problems, and best plants for reflected heat in Arizona covers the hardest spots in most yards.
• Hose off plants prone to spider mites about once a week.
• Pull weeds that come up after summer rain. Don’t let them set seed.

If summer is arriving earlier and hitting harder in your yard than it used to, how I’m adapting my low desert garden to earlier heat covers the changes I’ve made.

Frequently Asked Questions About August Gardening in Arizona

Additional Resources

Gardening in the desert comes with challenges you won’t find in general gardening advice, and you don’t have to work them out alone. My desert gardening resource page links to everything, from monthly planting schedules to summer survival strategies and winter frost protection.

For monthly classes online or in person, join me in the Growing in the Garden Academy. If August has been hard on your garden, the class on beating the heat in the low desert summer garden covers the practices that make the biggest difference.

Twice a month, I send my personal garden journal to members of the Growing in the Garden Academy. From the first seedling to the last harvest, you can follow what’s actually happening in my Mesa garden, including what failed. Members also get access to the past three years of garden journals and monthly classes.

Learn more about GITG Academy and low desert tips

Sources

1. Arizona Municipal Water Users Association. (2023). Landscaping with Style in the Arizona Desert. https://www.amwua.org/landscaping-with-style
2. University of Arizona Cooperative Extension, AZ1151. https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1151-2021%20%282%29.pdf