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Arizona Garden in May

This is a Growing in the Garden FREE Printable.
Download May Garden Checklist
May Garden Checklist

This blog post is your guide to May gardening in Arizona’s low desert. Learn what to prune, when to fertilize, how to adjust your watering schedule, and the best ways to protect your garden from rising temperatures.

As the heat sets in, May brings some of the most important garden tasks of the year. Mulching, watering deeply, and adding shade can make all the difference in helping your plants survive the looming high temperatures.

Garden with Shade
My Mesa, Arizona garden in May

Wondering what to plant this month? Head over to the What to Plant in May blog post for a detailed list of vegetables, herbs, and flowers that grow well in the low desert this time of year.

Download the May Garden Checklist at the top of this post to stay on track all month long.

This guide is designed for low desert gardeners in the Southwest—including areas below 3,500 feet in elevation like Phoenix, Tucson, and surrounding communities.


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


YouTube video
YouTube video

“It was such a pleasure to sink one’s hands into the warm earth, to feel at one’s fingertips the possibilities of the new season.”

~ Kate Morton, The Forgotten Garden

Vegetable Garden Tasks in May

A person wearing green gardening gloves is preparing soil in a raised garden bed divided into sections, with plants and mulch visible around the bed—an ideal scene for an Arizona Garden in May.

Prepare & Plant

  • Prepare garden beds before planting summer crops. Add compost and worm castings to improve soil health, and mix in a balanced organic fertilizer if needed.
  • Use shade strategically. Afternoon shade or shade cloth can help protect tender crops from the intense May sun. If you’re looking for the link to the shade cloth I use, I use this one and this one, too.
  • Apply mulch once your summer crops are growing well. A thick layer of mulch helps retain moisture, regulate soil temperature, and protect roots.
  • Start seeds indoors this month for your monsoon tomato planting. It’s also a good time to check your low desert planting list to see what else you can start from seed indoors.

Harvest

  • Tomatoes are usually ready to pick throughout May. Once nighttime temperatures stay above 75°F, fruit set slows, but existing fruit will continue to ripen. Pick tomatoes at the first blush of red and let them finish ripening indoors.
  • Beans are best harvested when the pods are small and tender. If left to mature, the pods swell with seeds, and the plant may stop producing.
  • Garlic and onions are typically ready to harvest this month.
    How to Harvest Garlic
    How to Harvest Onions
  • I’itoi onions can be harvested now or left in the bed. Wait until the tops completely die back for the best storage.
Harvest in May in Mesa, Arizona

Pest & Plant Care

  • Watch for squash bugs on summer squash. Check the undersides of leaves daily for clusters of eggs and adult bugs. Handpick when possible. If populations grow quickly, it may be best to remove heavily infested plants. Get more tips for controlling squash bugs here.

Summer Transition Tips

  • Consider using cover crops for any garden beds that won’t be planted in this summer. A summer cover crop keeps soil alive, shades the surface, and reduces erosion.
    Learn more about summer cover crops
  • New to gardening in the heat? Elevated Garden Bed Tips for Hot Climates is a great place to start if you’re working with a small space or just want an easier setup to manage.
Cover Crops
Cowpeas as a cover crop

Vegetable Watering Guidelines:

  • As temperatures heat up, annual vegetables will need more frequent watering. Water to a depth of about 8-12 inches every 2-5 days; allow the top of the soil to dry out before watering again. 
  • 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 percent on any size order.


Container Gardening

Grow Bags
Grow bags

As both cool-season and warm-season vegetables and flowers come to an end, it’s a good time to evaluate your container setup for summer.

Prepare for Summer Heat

  • Put small containers away until fall—they dry out too quickly in the summer heat. You can repurpose the soil as mulch in garden beds or add it to your compost pile.
  • Move remaining containers to areas that get natural afternoon shade, like the east or north side of your yard.
  • Group containers and grow bags close together to help insulate them and reduce heat stress.

Watering & Soil Care

  • As temperatures rise, monitor containers closely and water frequently.
  • If soil dries out completely, it can become hydrophobic (repelling water). Always check that water is soaking in and not running off the surface.
  • Consider adding ollas (unglazed clay watering pots) to help maintain moisture. I use ollas from Growoya.

Fertilizing Containers

  • Feed container plants about once a month with a low dose of water-soluble fertilizer like this one. Containers lose nutrients more quickly due to frequent watering.

If you enjoy container gardening, you’ll love the benefits of elevated beds—check out my guide, How to Grow in Elevated Garden Beds, to learn how to get started

For more container gardening tips, refer to my comprehensive guides to container gardening.

Filling up an oya in a container in an Arizona Garden in May
Filling an olla in a container

Flower Gardening

Larkspur blooming in May in Mesa, Arizona
Larkspur and California poppies

May is a beautiful time for flowers in the low desert—cool-season blooms begin to fade, and warm-season flowers take center stage. Here’s how to keep your flower garden thriving:

Care for Existing Blooms

  • Deadhead regularly to encourage continuous blooms. Remove spent flowers from zinnias, salvia, coreopsis, gaillardia, marigold, and cosmos.
    Read more about heat-loving flowers
  • Remove spent winter annuals that are fading in the heat to make room for summer blooms.
  • Mulch around flowers to help reduce soil temperature, retain moisture, and add organic matter to the soil.

Wildflowers

A close-up of a ruffled, pale peach-colored hollyhock surrounded by green leaves in an Arizona garden in May, with a soft focus on the background blooms.
Hollyhock bloom

Planting Warm-Season Flowers

  • Plant more warm-season annuals now, including sunflowers. I love this branching sunflower variety—it adds bright color and attracts birds.
  • Hollyhocks bloom from late April through June. Enjoy their beautiful display and save seeds to spread around your garden or share with friends.

Watering Guidelines for Flowers

  • As heat increases, water annual flowers deeply every 2–5 days to a depth of 8–12 inches. Allow the top of the soil to dry between waterings to prevent rot.

Rose Care

Rose
Eden climbing rose

Roses are still going strong in May. With a little care, they’ll continue blooming through early summer.

Ongoing Rose Care

  • Don’t worry about leaf cutter bees—the damage is only cosmetic and won’t harm your roses.
  • Deadhead spent blooms regularly to keep flowers coming through early summer.
  • Lightly fertilize roses this month to support continued growth and blooming. I use this rose fertilizer from Amazon. As temperatures rise, lighter doses of liquid fertilizer are easier on your plants if you want to continue feeding them.
Close-up of green rose leaves with semi-circular holes on the edges, likely caused by leafcutter bees. The image, taken in an Arizona Garden in May, is split into three vertical sections showcasing similar leaf damage.

Refresh and Mulch

  • If you’re growing alyssum around your roses, it may begin to fade in the heat. I let mine go as long as possible, then refresh the area once when the alyssum is done.
  • To mulch your roses for summer, apply a 1-inch layer of compost around the base of the plant, then top it with 3 inches of wood chip mulch.
    • The compost feeds the soil and supports healthy microbial activity.
    • The wood chips help retain moisture, protect the soil surface, reduce evaporation, and keep the root zone as cool as possible in the summer heat.

Roses typically stop blooming in the extreme summer heat, but this mulch layer can help them survive and recover once temperatures cool again.

For a complete guide to helping your roses get through the summer, see this hot summer rose survival guide.


Fruit and Fruit Tree Care

Mulberries growing in May in Mesa Arizona
Mulberries

May is an important month for fruit trees and berry plants in the low desert. Regular harvesting, careful watering, and a few key maintenance tasks can make a big difference in the health of your trees and the quality of your fruit as summer heat approaches. Here’s what to focus on this month.

Fertilize and Mulch

  • Fertilize citrus trees this month. Water well before and after applying fertilizer. Use an organic citrus fertilizer or apply compost and worm castings using this method.
  • Mulch around fruit trees with a 3–6 inch layer of organic mulch. Mulch helps lower soil temperatures, retain moisture, and improve soil health.
  • I’ve started feeding my fruit trees regularly with Nutrient+ from Arizona Worm Farm and have been very pleased with the results. It’s especially helped my trees recover from summer stress and damage. This year, I’m applying it before the heat sets in—hoping it will help strengthen and prepare the trees for the intense summer ahead.
Split image: Left shows a hand holding a bag of Espoma Organic Citrus-tone fertilizer; right shows a jug of Arizona Worm Farm Nutrient+—both ready to nourish my Mesa, Arizona garden in May against a backdrop of green leafy plants.

Harvest Time

  • Harvest strawberries, blackberries, and mulberries throughout May. Water strawberries consistently to prevent them from drying out. Blackberries are sweetest when they turn dull black, not shiny.
  • Early peaches and apricots are often ready this month. If birds start pecking the fruit, pick it slightly early and let it ripen on the counter. Learn more about growing peach trees here.

Pest and Disease Management

  • Clean up fallen fruit under both deciduous and citrus trees to help prevent pest and disease problems.
  • Support grapevines as they grow, and check the underside of leaves for grape leaf skeletonizer eggs. Remove and destroy eggs if you find them. If caterpillars appear, treat with Bt (Bacillus thuringiensis) before they spread.

Other Fruit Tree Care

  • Continue to thin fruit on deciduous trees to improve fruit size and overall health. Learn more about fruit thinning here.
  • Minor citrus pruning is fine this month. Remove suckers (shoots below the graft/bud union) and prune dead or damaged wood. Save heavy pruning for fall when temperatures cool.
Grapevine
Grapevines

Fruit Watering Guidelines: 2, 3

  • 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″.

Herb Gardening

Rosemary
Rosemary

Warm temperatures in May bring a new burst of growth to many herbs. With a few simple tasks, you can keep your herb garden healthy and productive through the summer months.

Care for Existing Herbs

  • Plant basil from seed or transplants this month. Keep basil regularly cut back to encourage full, bushy plants and a steady supply of fresh leaves.
  • Allow biennial herbs like dill, parsley, and cilantro to flower. Their umbrella-shaped blooms attract a wide range of beneficial insects, birds, and pollinators. As seeds form, collect them in paper sacks once they begin to turn brown.
  • Bay laurel grows well this time of year. Harvest bay leaves as needed.
  • Lemon balm and other herbs from the mint family thrive in the warmer temperatures of May. By now, frost-damaged or woody growth pruned in March should be filling in with new growth.
  • Cut back spent lavender flowers to encourage a tidy shape and additional blooming.
  • Fertilize summer-growing herbs such as basil by adding a layer of compost.
  • Apply mulch around the base of herbs to help retain moisture and regulate soil temperature.
  • Lightly prune borage after it has flowered to prevent excessive reseeding.
Arizona Garden in May
Parsley forming seeds

Watering Guidelines for Herbs

  • Annual herbs will need more frequent watering as temperatures rise. Water to a depth of 8–12 inches every 2–5 days, allowing the top layer of soil to dry out between waterings.
  • Desert-adapted perennial herbs, like rosemary, need deep but infrequent watering—about every 7–21 days, soaking to a depth of 18–24 inches.
  • Mediterranean herbs such as sage, rosemary, lavender, oregano, and thyme are more likely to suffer from root rot due to overwatering than from drought stress. During summer, it’s especially important not to keep the soil too wet—let it dry out between waterings.
Borage
Borage

Landscape Plants

Blackfoot Daisy
Blackfoot daisy

As the weather heats up, it’s still possible to plant summer-flowering shrubs and do some light maintenance in the landscape—just be mindful of timing and plant needs.

Planting and Spacing

  • It’s okay to plant summer-flowering shrubs this month. Be careful not to overplant—choose heat-adapted varieties and give each plant enough space to reach its mature size.
  • Avoid shearing shrubs into shapes. Instead, allow enough room for each plant to grow into its natural form without constant pruning.

Pruning Guidelines

  • Don’t prune newly planted trees or shrubs. Let them get established first.
  • Lightly prune dead or damaged branches on mature trees and shrubs as needed.
  • Save any heavy pruning for later in the fall when temperatures have cooled.
  • Trim spent blooms on spring-flowering perennials like Texas mountain laurel and penstemon to keep plants tidy.

Mulching

  • Apply a 3–6 inch layer of mulch around the base of trees and shrubs to reduce soil temperatures, retain moisture, and improve soil structure over time.

Landscape Watering Guidelines: 2

  • 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″).
  • High water use vines every 2-5 days (Water to a depth of 8-12″).
Lavender
Lavender


Further Reading:


Sources:

1 – For further reading, please refer to the original article: “University of Delaware Cooperative Extension. (2023). Key Strategies for Soybean Management.” https://sites.udel.edu/weeklycropupdate/?p=4489.

2 – 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.

3 – https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1151


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15 comments on "Arizona Garden in May"

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  1. Thanks for all your helpful information! It is greatly appreciated. Quick question for you; where can one find straw for mulching? I have used cedar chips, and wood chips, but both break down very slowly. I want to try straw. Happy gardening!

    1. Straw is a great option and it cools the soil very well. Unfortunately, I don’t have a local source to recommend. Check with local farmers or even online on apps such as offer-up. Best of luck with your garden!

  2. I am so glad I found your website. It is, by far, the most helpful resource for me here in my AZ garden. Thank you!

  3. When should I start Texas Star hibiscus from seed, inside or out? Thank you and keep up the great work

    1. I haven’t grown that before but it would probably be similar planting dates to okra or roselle hibiscus. Plant from seed or transplant by May.

  4. You are a life saver and a dear and I am so appreciative of the information you give to us! I have followed your guidelines for my backyard and “garden” adventure and so far you have given, by far, the best advice! I have more jalapenos than I know what to do with at the moment, my basil is thriving, and my Armenian cucumber plant seems to be doing well with a cucumber! This would not be the case unless I followed your advice and timing. Thank you for adding the landscape suggestions too!! Please keep that ongoing.

    1. I always water the same amount of time, but the length between watering is what changes. Right now I’m watering every 4 days, but will probably change that to every 3 days as we heat up.