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May Garden Checklist

Learn what to plant this month and get landscape maintenance advice for all Arizona elevations.

By Kelly Young

What to Plant

Low Elevations

SWEET POTATOES–These nutritious vegetables are simple to grow, and the plants are easy on the eyes, which makes them a popular summer ornamental in addition to being an edible garden staple. Scour nurseries for transplants, or produce your own slips, or sprouts, from a root. To do so, suspend a sweet potato in a wide-mouthed jar using three or four toothpicks to keep approximately half of the edible tuberous root above the lip of the jar. Fill the vessel with water and wait two to three weeks for the slips to sprout. Gently pull the slips from the tuber and plant them in garden soil that has been tilled to a depth of 4 inches. This will allow the roots to anchor and the new plants to start growing. Harvest leaves for salads or stir fries all summer. The roots can be dug up for eating in the fall.

WARM-SEASON VEGETABLES–Sow seeds of yardlong beans, Armenian cucumbers, Malabar spinach, okra and melokhia, a leafy green widely used in many African cuisines. Cover new plantings with floating row covers, available at most garden supply shops, to protect against whiteflies and other pests. Remove the covers when the first flower buds form so bees can reach the blossoms to pollinate them.

TREES, SHRUBS AND VINES–Heat-loving, desert-adapted types will fare best for late spring planting. Ironwood (Olneya tesota) is a Sonoran Desert native that will slowly grow to 30 feet tall and wide; Texas olive (Cordia boissieri) is a low-

May is the month to sow seeds of yardlong beans and other warm-season vegetables.

maintenance shrub with gray-green foliage and bright white flowers; and yellow orchid vine (Callaeum macropterum) can be trained to grow up a trellis or left unsupported to sprawl as a groundcover. Clear skies, low humidity and warm temperatures put new plantings at risk of drought stress. Wilting and curling leaves are ways the plant signals it is in desperate need for water.  Water every two or three days to keep roots from drying out.

Middle Elevations

PERENNIALS–To enjoy summer blooms year after year, plant desert marigold (Baileya multiradiata) for a pop of yellow. For purplish-red flowers, try Raspberry Delight sage (Salvia x ‘Raspberry Delight’). Milkweeds, such as Asclepias tuberosa, are a valuable food source for monarch butterflies.

The Highlands Center for Natural History in Prescott is scheduled to host its annual plant sale on May 2-3. Stop by and pick up some lovelies for your landscape, and get expert advice on gardening in the Southwest. Learn more at

Monarch butterflies are drawn to milkweed species, such as Asclepias tuberosa.

High Elevations

VEGETABLES–Sow seeds of leaf lettuce, kale, chard, beets, radish, carrots and turnips directly into garden soil. Transplant tomatoes and peppers. Cover any new plantings on nights when temperatures are expected to dip below 32 degrees to help protect against cold damage.

Garden Maintenance

All Elevations

MULCH–Mulch is a panacea for desert soil. It provides shade, slowing evaporation and preserving precious soil moisture, and protects against erosion, conserving valuable topsoil. As mulch slowly decomposes, it releases all of the essential nutrients plants require from the soil that would otherwise need to be supplemented with fertilizer. Layer wood chips, pine needles or commercially available mulch at least 3 inches deep over bare soil to reap all of the benefits.

Low Elevations

GIVE POLLINATORS A DRINK–There is usually very little measurable rainfall in the low desert during May, so give thirsty bees and butterflies some relief by setting out a shallow tray of water for them. To avoid potentially painful interactions with visiting bees, refresh the tray at night, after your guests have gone home.

HUNT FOR HORNWORMS–Check tomato, eggplant and pepper plants for hornworms, which are green caterpillars with a hornlike protuberance on their backs. You can find them hiding on the underside of leaves or resting on stems. Pluck them off and smash them or feed them to your chickens.

Middle Elevations

SCOUT FOR PESTS–Warm weather brings out plant-feeding pests. Look for spider mites on arborvitae, junipers and pyracantha by shaking the plants’ leafy twigs over a white sheet of paper. If present, the tiny mites will fall off and be seen scurrying across the paper. Manage infestations by hosing greenery down with a strong stream of water. Inspect stem tips of garden vegetables for aphids, and wipe them off with a damp cloth.

The Highlands Center for Natural History’s annual plant sale is scheduled for May 2-3. Visit for updates.

High Elevations

HILL APRIL-PLANTED POTATOES–“Hilling,” or mounding soil around potatoes once shoots reach 6 inches in height, encourages tubers to form along the stem and makes them easy to harvest. Pile the earth at least 4 inches above the soil line to prevent developing tubers from coming into contact with sunlight and “greening,” a process that can lead to the production of potentially toxic substances. Continue to hill potatoes until stems are 12 inches long.

Garden Solutions

Raccoons have been rummaging around in our north central Phoenix yard every night, emptying the bird feeders and even eating all of our carrots. We thought they were cute when they first started their visits, but not anymore. What can we do to humanely get rid of them?

Most wildlife is best enjoyed from a safe distance, and raccoons are a perfect example. These bold, beautiful masked critters should be discouraged from taking up residence in our home landscapes for several reasons. Their droppings are known to carry germs dangerous to humans and pets. And raccoons may become aggressive if they consider your home their territory. Discourage them by removing their favorite sources of food, water and shelter. Bring in your feeders at night, and consider leaving your garden fallow for the summer. Drain and dry fountains, cover hot tubs, and run automatic irrigation during the day when the cute bandits are less active. If the problem persists, hire a professional service that will humanely trap and remove them.

How often should a saguaro cactus be watered?

The answer to almost every plant-watering question begins with “That depends.” There are many factors that can determine the amount and frequency of irrigation. The plant’s age, health and location affect its water requirements. Saguaros, as a species, are adapted to the hot, dry conditions of the Sonoran Desert, but that doesn’t mean they don’t need supplemental water when grown in urban and suburban landscapes. A mature saguaro growing in a natural setting without interference from pavement or structures may only require extra water when rainfall is less than normal (8 to 12 inches a year). A newly planted saguaro in an urban landscape may need light irrigation every other week for the first year, with the time between watering gradually extended to once per month once its roots become established.

How can you tell when artichokes are ready to harvest?

The artichokes we eat are flower buds. If left to mature on the plant, they will eventually open into lovely purple thistle flowers. Once the bud starts to open, it is probably too fibrous to consume. Nobody enjoys eating prickly thistle flowers, no matter how pretty they may be. Knowing exactly when to harvest is a bit of a gamble: Pick too soon, and you have artichokes that are smaller than you may want. Wait too long, and they are inedible. It’s usually best to err on the “too soon” side. Cut the center bud when it is approximately 4 to 5 inches in diameter. Side buds are usually smaller than the center bud. Harvest those when they’re about 3 to 4 inches across.


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