Handout
Authors
Paul Larson
Laurie Vance
Deborah North
Publication Date: January 2025 |
View PDF
Cactus and desert adapted plants are the safe bet for planting in May as they love the heat, but there are still some veggie starts you can get in this month. Keep an eye on weeds as they are much easier to deal with before they die off and go to seed. Temperatures climb into the 90’s, but overnight temperatures are generally cool so start to shift your gardening schedule towards morning. Hydration is key this month for both you and your plants!
Jump To:
Maintenance
- Prepare for the extreme heat of summer. Check your irrigation system for leaks and perform maintenance as needed as outlined in Drip Irrigation: The Basics. Consider a free “water efficiency audit” of your home and garden, available to residents of the City of Tucson through the Zanjero Program.
- Most vegetables and many newly planted landscape plants will need some shade when temperatures reach 95 or more. One solution is a 30%-40% shade cloth. Maintain 3 inches of mulch to keep roots cool, suppress weeds, and reduce moisture loss. Leave 3” of clearance around trunks. Use of mulch is also good fire-wise strategy. Selecting, Planting, and Staking Trees and and Comparing the Ignitability of Mulch Materials for a Firewise Landscape have information about both.
- Citrus may drop some fruit; this is normal as the tree drops what it can’t support. They may drop old leaves to replace them with new ones. If you notice leaf curling, it may be a sign of drought stress. Refer to Diagnosing Home Citrus Problems and Oranges for Southern Arizona to learn more.
- Spray Italian cypress, juniper and other evergreens as well as roses and pyracanthas with a strong jet of water to remove spider mites. Yellowing needles or leaves and fine webbing are the first signs of spider mite damage. Inspect and take action if necessary at least weekly. Spider Mites has more information available.
- Leaf-cutter bees, one of our common pollinators, may cut circles in the new leaves of tender plants such as roses and bougainvillea. While unsightly, it does not harm the plant and no action is necessary, with Diagnosing Problems of Roses in the Landscape providing more information.
- Plan or install active or passive Water Harvesting systems to capture the rainwater before monsoon begins. Learn how by reading Landscape Management Practices to Optimize Passive Rainwater Harvesting and Plant Health and Harvesting Rainwater for Landscape Use.
- Pull dead annual wildflowers or collect their seeds.
Planting
- Plant heat loving flowers such as moss rose, gaillardia, zinnia, Madagascar periwinkle, verbena, celosia, and salvia, as well as desert-adapted perennials such as autumn sage, gaura, and bulbine. The Flower Planting Guide for the Low Desert has more information.
- Plant starters of basil, eggplant, and peppers into the soil. Plant seeds for cantaloupe, cucumber, peppers, watermelon, okra, cowpeas, asparagus beans (also called “yard-long beans,”) and summer squash. Plant sweet potatoes. Ten Steps to a Successful Vegetable Garden outlines planting steps.
- Plant and transplant agaves, palms, and other heat-loving plants such as desert trees.
- Plant heat-loving native or desert adapted trees. Plant or transplant palms.
- Remove pups from agaves & yuccas and transplant them if desired. If planting in a location without shade, consider adding shade cloth until they are established. Refer to How to Propagate Agaves and Cacti from Cuttings and Seed for steps.
- Plant or transplant cacti this month because the warm soil temperatures facilitate root growth. Raised, slightly mounded, and open locations with fast-draining soil provide good homes. Plant at the proper depth and orient in the same direction. This helps the plant adjust and limits the risk of sunburn. If the original orientation is unknown, protect the cactus with at least 30% shade cloth until new growth appears. Reference Cactus, Agave, Yucca, and Ocotillo, How to Transplant a Cactus, and Problems and Pests of Agave, Aloe, Cactus, and Yucca.
Fertilizing
- For oranges, tangerines, and grapefruit, this will be the 3rd of 3 annual feedings for these varieties of citrus. Lemons are later. Evenly spread it under the tree, starting one foot from the trunk and continuing out several feet. Water the fertilizer into the soil immediately after applying. If young leaves remain yellow, apply chelated iron to the soil following label directions. For information on amounts, reference Citrus Fertilization Chart for Arizona.
- Fertilize palms in mid-spring and early summer, ensuring thorough watering within 24 hours. Use a palm-specific fertilizer, which typically contains about three times more nitrogen and potassium than phosphorus (the first and third numbers on the bag are about three times the middle number). These fertilizers also include magnesium (Mg) and other essential micronutrients tailored for palms. Learn more in Arizona Landscape Palms.
- Fertilize roses every 3-4 weeks.
- Fertilization is not necessary for native cacti but will benefit flowering hybrid cacti such as trichocereus species. If used, apply an all-purpose fertilizer at no more than half-strength.
Watering
- May is one of the hottest and driest months of the year, often with hot, dry winds. Plants need more frequent irrigation to keep them healthy, as outlined in Watering Trees and Shrubs.
- Vegetable and flower gardens may require daily watering.
- Non-desert trees and shrubs will need a good soaking every 7-10 days. Use a soil probe to assure water is getting down to a 24” depth for shrubs and 36” for trees.
- Desert-adapted trees and shrubs may require a soaking irrigation once this month to prevent drought stress. Water slowly to reduce runoff and you need to reach the same depths as above.
- Cacti generally do not require irrigation, but during a particularly dry summer they will benefit from some irrigation – but no more than every two weeks.
- Bermudagrass should be irrigated to a maximum depth of 6” every three days. Turfgrass Maintenance Guide for Residential and Commercial Lawns in the Low Elevation Arizona Desert has more information.