August Gardening Tasks for Arizona’s Low Desert

By: Angela Judd | July 31, 2024

This is a Growing in the Garden FREE Printable.

Arizona gardens often suffer from heat and neglect in August. However, as the next planting season approaches, it’s time to prepare the beds and plan for fall. This article covers the essential tasks to help your August garden vegetables, fruit, flowers, and landscape plants thrive. We will also cover which pests to expect and how often to water your garden, trees, and shrubs.

For information about what to plant and harvest in the low desert during August, please see my planting guides or this blog post, “What to Plant and Harvest in August: Low Desert of Arizona.” Low desert includes elevations below 3500 ft in the Southwest, such as the Phoenix and Tucson metro areas.

Click on the title to jump to that section and learn more about what to do during August:

Vegetable Gardening
My August Garden Journals
Pests & Wildlife to Watch Out For This Month
Container Gardening Tasks
Flower Gardening Tasks
Caring for Roses During August
Herb Gardening
Fruit Trees and Citrus
Landscape Plants
August Watering Guidelines

Vegetable Gardening

Plan Your Fall Garden

Read “How to start a garden in 8 simple steps” to get started on your garden if you are a first-timer or are looking for a few tips.
Make a plan for fall and winter planting. We usually don’t have enough room to grow everything we want. Think about what is most important to have fresh from the garden. Incorporate different vegetables, herbs, fruits, and flowers into your garden plan.
If you want to grow garlic, purchase garlic if you haven’t already. Store it in the fridge until it is time to plant in October.
If you want to plant potatoes next month, purchase organic potatoes and begin chitting them. Learn how here.

Prepare Beds For Fall Planting

To prepare beds for fall planting, add compost, spent cover crops, worm castings, and other organic matter to the soil. Organic matter decomposes and needs to be replenished.
If your garden has struggled or has not grown well, consider testing your soil. Then, amend the soil as directed by the soil test. This is the soil testing kit I use.
If you are not going to plant until September or October, plant a cover crop like buckwheat or cowpeas to cover the soil.
Cut back cover crops 2-3 weeks before you plan to plant. Cut off at soil level. Pull back the mulch and leave plants on the soil or cover with compost. Learn more about how to grow cover crops here.

Garden Tasks During August

Remove spent summer-heat-loving vegetables and vegetables past their prime.
Cut back peppers, eggplants, and tomatoes to the newest leaves. This rejuvenates the plants for an excellent fall crop. After cutting back, top plants with worm castings and compost.
Remove debris around plants to discourage pests.
Remove spent artichoke heads to save the seeds.
Harvest any remaining I’itoi onions.
Pot up any indoor-grown seedlings that are outgrowing their containers if it is not time to plant them outside.
Fertilize indoor-grown seedlings every other watering.

August Gardening Tasks for Low Desert Arizona Gardens

My August Garden Journals

Twice a month, I send my personal garden journal to members of “Growing in the Garden Academy.” From the first seedling to the last harvest, you can follow my gardening adventures in Arizona’s unique low desert. As a member, you also have access to the past three years of garden journals and monthly classes.

Join me, and let’s make your garden thrive under the desert sun!

Learn more about GITG Academy & Low Desert Tips

Low Desert Arizona in August: Pests & Wildlife to Watch Out For This Month

The best defense against pests is healthy plants. This can be difficult because the heat is stressful for plants. Spend time in the garden each day and catch problems when they are small.

Grasshoppers show up to feed on new growth. Handpick. Hopefully, the birds help you out, too.
Spider mites can be problematic this month. Read this post for treatment options.
Squash and Eastern Bordered Plant Bugs. This article shares prevention and treatment options.
Whiteflies thrive in August garden conditions. They look like clouds coming off the bottom of leaves when a plant is disturbed. Use a soapy water solution of 1 Tablespoon Dawn to one gallon of water on the undersides of leaves daily to keep infestations down.
Corn borer larvae cause skeletonized patches on corn leaves. Treat with Bt or a drop of mineral oil on top of each tassel.
Bird damage on melon and sunflower leaves. Although they damage the leaves, the plant usually survives. Consider putting out a bird bath for thirsty birds.
Chrysanthemum lace bugs on sunflowers. Read this post for treatment options.
Bagrada bugs, tomato hornworms, three-lined potato bugs, and leaf-footed bugs are common this month. Hand-pick all stages and drop into soapy water.
If rollie-pollies are eating seedlings (they love beans!), sprinkle a small amount of this slug and snail bait when you plant. Learn more in this blog post.
Milkweed and other seed bugs are common on seed pods and best left untreated; they usually don’t cause damage.
Leaf miners on cantaloupe or other melons. Remove damaged leaves.
The buzz of cicadas fills the air, and their exoskeletons can be found all around the yard. Damage is minimal; they are seasonal, and there is no need to treat for them.

Beneficial insects and other wildlife you may see during August:

Lovebirds and finches on sunflowers, bees, assassin bugs, wasps, hummingbirds, praying mantids, lizards, and butterflies like Swallowtails and Gulf Fritillary.

Container Gardening Tasks

Move containers to areas of your yard that receive afternoon shade naturally.
Group containers and grow bags close together for an insulating effect.
Refresh large containers with additional raised bed mix if you are planting in them. Organic matter decomposes and needs to be replenished. I love this soil mix for raised beds and containers.
Keep those small containers put away for at least another month.

Arizona August Garden Tasks: Flower Gardening

Keep summer bloomers like zinnia, vinca, cosmos, and gaillardia deadheaded to encourage more blooms.
Don’t cut anything back severely; it probably won’t recover.
Plan your wildflower garden for fall. Learn more here.
Fertilize container-grown flowers this month.
Save seeds from summer flowers like sunflowers, marigolds, tithonia, zinnias, and four-o-clocks. Learn how to save seeds here.
If you haven’t already, order fall-planted bulbs like ranunculus, prechilled tulip bulbs, and anemones. (Click the links for bulb sources). Store ranunculus and anemone corms in a cool closet until it’s time to plant. Read grow guides for ranunculus and anemones here.
To remove spent sunflowers, don’t pull them up! Cut them off just above soil level, and the roots will decay instead of pulling a large soil ball with them.

Arizona Annual Flowers Planting Calendar helps you learn when to plant flowers in Arizona and when to start seeds indoors.

Caring for Roses During August in Arizona

Evaluate your roses. They may look haggard, but if plants are severely burned or struggling, consider moving them to a shadier location in the fall.
Roses are often chlorotic, as it is difficult for them to access soil nutrients when it is so hot. As the soil cools, the plant will begin to take up the nutrients.
Keep roses lightly deadheaded (I cut off just under the bloom). Do not fertilize or prune this month.
Remove roses right away from stressed plants. Blooming adds additional stress.
Make plans for fall planting. Choosing the right varieties helps ensure your roses survive the summer heat. Roses such as Memorial Day, Iceberg, and Julia Child are excellent choices as they are known for their resilience and ability to withstand high temperatures. Adding more roses to your garden? I get my roses from Heirloom Roses. Use Code GARDENAZ24 for 20% off any rose order through December 31, 2024.

Fruit and Fruit Trees

Keep fruit picked on fruit trees. Clean up rotten, split, sun-damaged, or fallen fruit.
Don’t prune this month.
Apply the last round of citrus fertilizer to citrus between August and September. Water well the day before you fertilize and again after fertilizing.
Lemons and key limes begin to ripen this month. Harvest as needed. They will continue to ripen over the next several months. The flavor is best right after picking. Lemons can be stored in the fridge for a couple of weeks, but it’s best to leave lemons on the tree until needed. Read this article for citrus growing tips.
Watch pomegranate trees for leaf-footed bugs.
Expand the basins around trees to extend 1 foot beyond the drip line as needed.
Root strawberry runners to make new plants.
Split fruit (tomatoes, pomegranates, citrus) is a watering issue. Remove split fruit and do your best to provide regular deep watering for plants.

Herb Gardening

Perennial herbs may look a little spent. Continue to harvest as needed, but wait until September to give them a good trim and decide if you want to replant. Learn more about growing perennial herbs in this article.
Harvest and use basil. Cutting back basil often encourages new growth and keeps it from flowering and going to seed. This article shares how to grow basil.

The Arizona Herb Planting Guide helps you learn when to plant over 30 different herbs in Arizona and whether to plant seeds or transplants.

Landscape Plant Tasks in August

August is a good time to plant hardy desert trees and cacti. Their roots get established best in warm soil.
Wait to plant shrubs and perennials. It’s too hot. They will establish much better if you plant them in the fall.
To encourage more blooms, deadhead and lightly prune summer flowering plants and perennials such as oleanders, birds of paradise, Texas sage, and lantanas.
If cactus are leaning, this indicates a problem with the root system. This can be caused by too much or too little water. Plants may fall over. Contact a professional for assistance if the saguaro is over 8 feet tall.
Do not top trees. It’s damaging to the plant. Thinning limbs to open up the canopy is okay.
If a limb breaks during a summer storm, prune back to a main branch and make a clean cut. Clean cuts will heal better.
Evaluate severely stressed or unhealthy plants. Typical reasons for not growing well are not enough water, too much sun (or shade), or the plant is not suited for a desert climate. Make a plan to move or replace struggling plants in the fall.
Hose off plants prone to spider mites about once a week.
Pull weeds that emerge after summer rains. Do not let them set seed.

Arizona Garden in August Watering Guidelines

Hopefully, we will get nice soaking rain. If you receive .5″ rain, you can probably skip one watering.
Think about ways to harvest or channel rainfall and direct it on your property. Read this post to learn more about using rainwater harvesting and swales and berms to collect and use rainwater.
Use a soil probe to check watering depths. Aim to water trees to 3 feet, landscape plants to 2 feet, and annual plants to 1 foot.
The summer heat and dry soils build up salt levels in the soil. Local water supplies also become saltier later in the summer. Water twice as deep once this month to flush salts from plants’ root zones.
If you haven’t already, check the irrigation system and timer. Run the system, inspecting all drips and sprinklers for leaks and proper watering.

Watering Containers During August

With hot temperatures, monitoring containers closely and watering often is crucial. You may have to water every day. If you’re not sure, use a moisture meter to check soil moisture levels

If containers dry out too much, the soil may become hydrophobic. When watering, check the soil to ensure water is absorbed and not repelled by hydrophobic soil. I usually water my containers every 2-3 days in August and fill up the ollas each time I water. Adding ollas to containers helps with watering during the summer. I use ollas from Growoya.

Watering Annuals and Garden Beds During August

During hot weather, annual vegetables, herbs, and flowers need more frequent watering. Water to a depth of about 8-12 inches every 2-3 days, allowing the top of the soil to dry out before watering again.

I usually water my raised beds every 2-3 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 GITG5 to save 5 percent on any size order.)

Tree and Vine Watering Guidelines: ¹, ²

Monitor your fruit trees for signs of water stress. Leaf curling is usually the first noticeable sign. Wet the soil from the tree trunk to just past the tree’s drip line.

Established citrus trees should be watered once every 7-14 days to a 2-3 feet depth.
Water annual fruit and high water use vines every 2-5 days to a depth of 8-12″.
Water established fruit trees every 7-10 days to a depth of 18-24″.
Grape vines need deep watering every 5 days.
Water annual fruit and high water use vines every 2-5 days to a depth of 8-12″.
Desert-adapted trees, shrubs & vines every 7-21 days (water to a depth of 24-36″ trees / 18-24″ shrubs / 8-12″ vines).
High water use trees every 7-10 days (water to a depth of 18-24″).
High water use shrubs every 5-7 days (water to a depth of 8-12″).

Sources:

1 – For additional information on watering practices, visit: “Association of Municipal Water Users Authority. (2023). Landscaping with Style in the Arizona Desert.” https://www.amwua .org/landscaping-with-style.

2 – https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1151-2021%20%282%29.pdf