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Arizona Garden in May

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The heat brings important garden tasks—mulching and providing shade are two of the most important ways to help the garden survive the summer. This blog post is designed to help you with the necessary gardening tasks during May, including when to water and what to plant, prune, and fertilize.

Keep reading for garden inspiration, a May garden task checklist, and a list of vegetables, herbs, and flowers to plant in your low desert Arizona garden in May. Low desert includes elevations below 3500 ft in the Southwest, such as the Phoenix and Tucson metro areas.

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

• Vegetable Gardening
• Container Gardening
• Flower Gardening
• Fruit & Fruit Trees
• Herb Gardening
• Landscape Plants
• Vegetables, herbs & fruit to plant outside in the low desert in May
• Vegetables, herbs & fruit seeds to plant indoors in the low desert in May
• Flowers to plant in the low desert in May
• Flower seeds to start indoors in the low desert in May

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“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

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Vegetable Gardening in the Low Desert Arizona Garden in May

• Use shade cloth to provide shade for annual vegetables or plant them in areas that receive afternoon shade. I use this shade cloth.
• Prepare garden beds before summer planting – Add compost and other organic matter to the soil. Add a balanced fertilizer if needed. 
• Once summer crops are planted and growing well, apply a thick layer of mulch to your garden beds.
• As cool and warm-season crops finish, consider planting a cover crop in empty beds to keep soil alive over the summer. Learn more in this article.
• May is an excellent month for tomato harvests. Once nighttime temperatures are over 75°F, tomato pollen may not be viable, and new fruit may not form.¹ Existing fruit will continue to ripen.
• Summer squash grows quickly. Check the undersides of leaves daily for squash bugs. Handpick adults and remove eggs. If populations climb, consider removing affected plants.
• Plant Armenian-type cucumbers for cucumber harvests all summer long.
• Harvest beans when they are small and tender. As beans mature, they lose flavor and the pods begin to bulge with seeds, signaling the plant to stop producing.
• Start seeds indoors this month for a monsoon tomato planting. Check planting lists for additional seeds to start indoors.
• Harvest garlic and onions this month. Click on the links to read articles with harvesting tips.
• You can harvest I’itoi onions this month. You can also leave them in the beds – the tops will die back. Harvest when the tops completely die back.
• In this article, learn more about using cover crops during summer to improve garden soil.

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 GITG5 to save 5 percent on any size order.

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Container Gardening

• As cool-season and warm-season vegetables and flowers finish up, put small containers away until fall. Use the soil from containers as mulch or add to compost.
• Move the remaining containers to areas of your yard that receive afternoon shade naturally.
• Group containers and grow bags close together for an insulating effect.
• Plants in containers should be fertilized with a low dose of a water-soluble fertilizer like this one about once a month.
• Plant container-grown roses this month on the north or east sides of the yard that receive afternoon shade in the summer. Use as large a container as possible—ideally over 10 gallons; 20 is even better.

Container Watering Guidelines:

• As temperatures heat up, it’s crucial to monitor containers closely and water often.
• 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.
• Add ollas to containers to help with watering during the summer. I use ollas from Growoya. For a discount, use code GROWING.

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Flower Gardening in the Low Desert Arizona Garden in May

• Allow wildflowers to form seeds. Remove spent plants and shake plants to drop the seeds in place. This article explains more about wildflowers.
• Plant sunflowers. Pops of yellow flowers brighten up a summer yard and attract birds. I love this branching variety.
• To extend bloom, deadhead annual warm-season flowers such as zinnias, salvia, coreopsis, gaillardia, marigold, and cosmos. Read this post to learn about flowers that love hot summers. .

• Roses continue to bloom this month. Keep spent blooms deadheaded and enjoy the blooms. Fertilize roses this month. I like this fertilizer from Amazon. Plant container-grown roses this month on the north or east sides of the yard that receive afternoon shade in the summer
• Hollyhocks put on a show in late April through June. Enjoy the prolific blooms. Save seeds to spread around your yard and share with friends. 
• Remove spent winter-growing annuals.
• Plant more warm-season annual flowers this month.
• Apply a thick layer of mulch around the base of flowers. Mulching reduces soil temperatures and adds organic matter to the soil. 

Flower Watering Guidelines:

• As temperatures heat up, annual flowers 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.

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Fruit & Fruit Trees

• Fertilize citrus this month. Water well before and after applying fertilizer. Use an organic fertilizer like this one, or use compost and worm castings with this method.
• Apply a 3-6 inch layer of mulch around the base of trees. Mulching reduces soil temperatures and adds organic matter to the soil. 
• May in Arizona means mulberry, blackberry, and strawberry harvests. To prevent strawberries from drying out, water strawberries regularly during May. Blackberries are sweetest when “dull black”. 

• The early-ripening varieties of peaches and apricots are often ready to harvest this month. If you notice the birds are beginning to peck them, harvest the fruit a little early and let it continue to ripen on the counter. Read this article for more information about how to grow peach trees.
• Clean fallen fruit from deciduous and citrus trees to discourage pests and disease. 
• Provide support for grapevines. Check the underside of grape leaves for skeletonizer eggs; if found, remove and destroy eggs. If you see caterpillars, use Bt (Bacillus thuringiensis) to control them before they overtake grapevines. Bt is available on Amazon.
• Continue to thin fruit as needed on deciduous fruit trees. This article helps explain the process. 
• Minor citrus pruning is okay. Prune suckers (shoots growing straight up below the bud union) and dead or damaged wood on citrus and other fruit trees, but delay heavy pruning until later in the fall.

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″.

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Herb Gardening in the Low Desert Arizona Garden in May

• This month, continue planting basil from seed and setting out transplants. Keep basil cut back to ensure full plants and plenty of basil.
• Allow biennial herbs like dill, parsley, and cilantro to flower. The umbel flowers attract many beneficial insects, birds, and pollinators.
• Bay laurel grows well this month. Harvest as needed.
• Lemon Balm and other members of the mint family love the warmer temperatures of May. Hopefully, frost-damaged or woody growth was pruned in March, and new growth is filling in. 
• Cut back spent flowers on lavender.

• Fertilize summer herbs such as oregano, basil, and mint with an organic fertilizer or top with additional compost. 
• Apply a thick layer of mulch around the base of herbs.
• Lightly prune spent borage branches to prevent excessive reseeding.

Herb Watering Guidelines:

• As temperatures heat up, annual herbs 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.
• Water desert-adapted landscape perennial herbs (like rosemary) every 7-21 days (water to a depth of 18-24″).
• Many Mediterranean herbs, such as sage, rosemary, lavender, oregano, and thyme, are more likely to die from overwatering and root rot in the summer than from underwatering. Therefore, take care not to overwater them.

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Landscape Plants

• It is ok to plant summer flowering shrubs. Do not over-plant; be aware of the plant’s mature size and space accordingly.
• Do not shear plants into shapes. Instead, allow enough room between plants so they can grow to a natural size and shape.
• Do not prune newly planted trees or shrubs. 
• Light pruning of dead branches from established trees and shrubs is okay. Heavy pruning should be delayed until later in the fall.   
• Lightly prune spent blooms on spring-flowering perennials like Texas mountain laurel and penstemon. 
• Apply a 3-6 inch layer of mulch around the base of trees and shrubs if possible.

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″).

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Vegetables, herbs & fruit to plant in the low desert in May

(Click the link to read “How to Grow” articles on my website.)

SEED, TRANSPLANT, OR BOTH? S = Seed / T= Transplant

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Vegetable, herb & fruit seeds to start indoors in May

(Click the link for seed sources.)

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Flowers to plant in the low desert in May

(Click the link to read “How to Grow” articles on my website.)

SEED, TRANSPLANT, OR BOTH? S = Seed / T= Transplant

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Flower seeds to start indoors in the low desert in May

(Click the link for seed sources.)

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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. 

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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/az1151-2021%20%282%29.pdf

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