Summer Garden Checklist
Learn what to plant this season and get landscape maintenance advice for all Arizona elevations.
By Kelly Young
What to Plant
WARM-SEASON VEGETABLES–Sow seeds of heat-loving black-eyed peas, yardlong beans, Armenian cucumbers, okra, purslane, Malabar spinach and roselle. Transplant sweet potatoes to an area where the lime-green vines can spread at least 3 feet wide and long. Once the monsoons bring higher humidity and some cloud cover later in July, plant corn, cantaloupe, winter squash and pumpkins from seed. Protect new plantings from whiteflies and other pests with floating row covers, available at most garden stores. When the first blooms appear, remove the covers to let bees in to pollinate.
PALMS–Transplant palms into a hole that is as wide as the plant canopy but only as deep as the root ball. If the hole is too narrow, roots may struggle to colonize the soil. If the hole is too deep, soil may get packed against the palm trunk and put the tree at risk of infection by soil-borne diseases. Consider Senegal date palm (Phoenix reclinata), a tropical species that performs well in the Arizona heat and produces edible dates that attract birds.
COVER CROPS–Enrich the soil for fall planting by sowing seeds of black-eyed peas, which promote soil health in a number of ways: They add organic matter, which makes desert soils “softer” and thereby easier to work with while improving soil moisture retention. Also, pea plants accumulate nitrogen. When the plant is chopped and left to decompose in the soil, its nitrogen is released and available for use by nearby flora. Place seeds close together—2 to 3 inches apart. Once most of the plants are blooming, approximately 45 days after planting, cut vines down and let them decompose, either on the soil surface or mixed into the top 6 inches of earth before planting fall crops. Make sure to chop them down before the flowers become seed pods, otherwise the nitrogen will be “locked up” and unavailable for uptake by neighboring plants.
SUNFLOWERS–Sunflowers attract birds and beneficial predatory insects and spiders to the garden while also offering beautiful blooms and edible seeds. The variety ‘Skyscraper’ can reach an impressive 12 feet in height. If sky-high stalks aren’t for you, try ‘Sunny Bunch,’ which has bright yellow flowers and only grows to 3 feet high. Follow guidelines on the seed package for spacing instructions and protect emerging seedlings from being devoured by hungry birds by covering the young plants with floating row covers until they have grown three or four leaves.
Middle and High Elevations
TREES AND SHRUBS–Invest in the future by planting hardy, low-maintenance Arizona natives. Alligator juniper (Juniperus deppeana), named for its distinctive bark that resembles alligator skin, is a multibranched evergreen tree that grows to 40 feet tall and 20 feet wide. Fremont barberry (Berberis fremontii) is a semi-evergreen shrub, meaning it may drop its leaves in late winter only to immediately replace them. Barberry produces yellow flowers, followed by pretty purple fruits that are dry at maturity. Plant it where it has at least 12 feet to grow both high and wide.
WARM-SEASON VEGETABLES–Transplant eggplant,
peppers, squash, tomatoes and cucumbers. Corn, okra and beans can be planted from seed. For better kernel production, plant corn in blocks, or several short rows next to each other, rather than in single, long rows. Each kernel of corn requires a pollen grain to develop. If adequate pollen does not reach the developing ear, there will be poor kernel production. By planting corn in blocks that are roughly as wide as they are long, the pollen has a better chance of hitting the target.
COOL-SEASON VEGETABLES–Beginning mid-July, sow carrot, radish, turnip, beet, leaf lettuce, mustard green and chard seeds. Transplant cauliflower, broccoli and Brussels sprouts, keeping in mind that adult plants need to be spaced at least 2 feet apart.
VEGETABLES–Sow seeds of sweet corn, cucumber, radish, beet, leaf lettuce and squash by early July so they will be ready for harvest before cold weather sets in. Plant head lettuce, tomato, cabbage and Brussels sprouts by mid-June.
FLOWERS–Spread seeds of summer annuals on soil that has been lightly tilled and raked smooth to ensure easy germination and rooting. If you prefer to get a head start on having warm- weather blossoms, pick up multipacks of transplants at your local nursery. Cosmos, sweet pea, calendula, marigold, nasturtium, petunia, snapdragon, stock and pansies are sure to give a splash of color and sweet scent to any garden.
SUMMER BULBS–Plant gladiolus, begonia, tuberose, elephant ears, dahlias, cannas and callas by mid-June for summer blooms. Dig the planting hole two to three times the depth of the bulb; in the bottom, sprinkle a phosphorus-rich fertilizer, such as rock phosphate or bone meal, to support big, showy blossoms.
MONITOR SOIL MOISTURE–Plant water requirements reach their peak in June and begin to taper off once the summer monsoons bring higher humidity and occasional rain showers. To learn more about how much and how often to water your landscape, check out the interactive plant watering guide at wateruseitwisely.com/100-ways-to-conserve/landscape-watering-guide/plant.
SOLARIZE GARDEN BEDS–Harness the power of the summer sun to kill pests lurking in the soil. Till flower and vegetable beds to loosen the soil and expose buried weed seeds, water to a depth of 12 inches (use a long barbecue skewer or soil probe to measure), then cover the ground with clear plastic, which will trap heat and moisture. Mound soil around the edges of the plastic to trap the heat inside and leave the plastic in place for at least 6 weeks.
Middle and High Elevations
MANAGE WEEDS–Summer showers usher in a new generation of weeds, which are easiest to remove when they have only one to two leaves and underdeveloped roots. Use a hoe to lightly scratch them from the soil, or spray them with a natural herbicide that contains the active ingredient pelargonic acid. Always follow the directions on the product label.
We recently bought a home in North Scottsdale that sits on a rocky hillside. What can we plant that will attract birds but won’t block our view?
Birds gravitate to landscapes that offer food or shelter for roosting and nesting. Many Sonoran Desert native plants fit the bill and are also relatively low-growing. For example, brittlebush (Encelia farinosa) produces yellow daisylike flowers in late winter/early spring, followed by seeds that are beloved by many local and migrating songbirds. Several species of cholla cactus, including staghorn cholla
(Cylindropuntia versicolor), are favorite nesting sites for cactus wrens and curved-bill thrashers. And chuparosa (Justicia californica) is a delicate, viney shrub with tubular red blossoms that draw in hungry hummingbirds. Once any of these plants are established, which can take two to three years, they will require minimal maintenance or supplemental irrigation. Just sit back with your binoculars and enjoy the show.
There are clusters of white powder on my cantaloupe leaves. I already pulled one of the vines up because it wilted and died a few weeks after the snowy substance appeared. What is causing this, and what should I do to protect my crops?
It sounds like your cantaloupes have been infected with powdery mildew, a type of fungal disease. Once established on garden plants, this malady is extremely difficult to cure. Your best bet is to remove all infected plants, bag them and send them to the landfill. Disinfect all tools that have had contact with the diseased vines with a 10% bleach solution, which can be made by mixing one part chlorine bleach with nine parts tap water. To avoid future infections, select melon varieties that are labeled as “powdery mildew-resistant,” plant them in full sun, and keep the area weed-free so air can easily circulate, thereby creating an environment hostile to the fungus.
Can pistachios grow in Arizona?
Yes, pistachios can be grown in some areas of Arizona. The trees thrive in regions with low humidity, hot summer days and cool winter nights. Most successful pistachio trees in Arizona are found at elevations between 2,500 and 5,000 feet in soils that are well- drained and loamy, meaning there are roughly equal parts sand, silt and clay. You can have your soil tested by a laboratory to determine if it is loamy, or test it yourself using the feel method. To learn more about this, download the “Determining Soil Texture By Feel” chart at extension.arizona.edu. Keep in mind that pistachios have separate male and female plants. Nuts grow on the female plants, but a male must be nearby to provide the necessary pollen to trigger fruit development. Many nurseries and tree farms throughout the state offer pistachio trees.