Home » Desert Gardening » Monthly Guides

Arizona Garden in May

---

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.

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:

• May YouTube Videos
• Vegetable Garden Tasks in May
• Container Gardening
• Flower Gardening
• Rose Care During May
• Fruit & Fruit Trees
• Herb Gardening
• Landscape Plants
• Sources

---

---

“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

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.

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.

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

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.

---

Flower Gardening

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

• Let wildflowers go to seed by leaving the plants in place. Shake them gently to drop seeds for next season.
  → Learn more about saving wildflower seeds

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

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.

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

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.

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.

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

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.

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.

---

Landscape Plants

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″).

---

---

Further Reading:

• Arizona Vegetable Planting Guide helps you learn when to plant vegetables in Arizona and whether to plant seeds or transplants.
• Arizona annual flowers planting guide helps you learn when to plant flowers in Arizona and whether to plant seeds or transplants.
• Would you like more information about gardening in Arizona? This blog post shares 7 tips for growing a vegetable garden in Arizona. 
• Arizona Herb Planting Guide features pictures and planting dates for nearly 40 herbs that thrive in the low desert of Arizona.

---

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

---

Was this post about gardening in Arizona during May helpful?
If so, please share it with a fellow gardener—it helps more than you know!