Gardening Calendar for the Southwest

July through August and sometimes September:
The long, hot days of summer


Plant or Transplant Palms. Palms establish better during summer--the warm soil encourages rapid growth of the grasslike roots. Set out new plants from containers or transplant young palms July or August.

Vegetables. Continue to sow seed of sweet corn and summer squash directly in the garden. Plant corn at 3-week intervals for a succession of  harvests. In August, start seeds of cool-season vegetables in pots and they'll be ready to transplant to the winter garden by mid-September.

Soil Prep for Planting. New lawns, as well as vegetable and flower beds, prefer a well-prepared soil high in organic matter. Late in August, add a 3- to 4-inch layer of ground bark products or compost, plus 1 pound of ammonium phosphate per every 100 square feet over the planting area. Mix into the top 8 to 10 inches of soil. Dig planting holes (start early in the morning when it's cool) for trees and shrubs you'll plant from containers September and October.



Summer is the time to be diligent when watering. Container plants and those recently planted have little margin for error. Forget to water them properly during the next few months may cause their death. Water such plants every day, or at least a few times a week. Established trees and shrubs will generally do with a good soaking once or twice a month, depending on amount of rainfall received. Best time to water is early in the A.M. to hydrate plants for the long, hot day ahead.

Monitor Summer Rains. From now until about mid-September, some lucky regions in the Southwest will benefit from the localized summer storms called monsoons. Your landscape plants will appreciate the cooling showers, but the rain often doesn’t do as much good as you might imagine. Dig down near plant roots to see if enough moisture soaked into the soil to count for an irrigation.

Mulch to Conserve. Add a 3- to 4-inch layer of mulch--compost, ground bark, or shredded fir bark--over the root area of landscape plants and around summer vegetables such as tomatoes, squash, beans and peppers. It conserves the water you or mother nature applies plus cools the upper layer of soil.



Prepare for Strong Winds. A  counterpart to summer rains are strong, sometimes violent winds. Avoid heavy irrigation if you know heavy winds are in the forecast--young trees can be blown over in saturated soil. Lightly thin canopy-shaped trees (such as some mesquites and acacias) so breezes can pass through branches rather than catching “umbrella-style.”

Control Garden Pests. Summer is the most active time of year for pests. Get in the habit of inspecting your plants at least once a week (vegetables and fruits even more often) during the warm season to catch pest and disease damage early. Be on the lookout for spider mites; they set up housekeeping on the undersides of leaves. Stippled yellowing leaves and fine webbing are signs of their activity. Wash leaves clean with water and spray infested areas, especially leaf undersides, with insecticidal soap. Grape leaf skeletonizers come and go through summer. Watch for the slow-moving black moths as they fly around your vines, looking to lay their eggs. Examine undersides of leaves for the egg clusters or the black and yellow caterpillars. Clip and destroy infested leaves.

Weed Patrol. Pre-emergent sprays kill weed seeds before they germinate. Apply them late June to early July before moisture from summer rains prompts the summer crop. Weeds that do sprout thrive in the summer heat, especially if summer storms are generous. Once a downpour ends, take advantage of the moist ground and pull weeds--roots and all. Don’t drop them--toss them--into the trash or compost pile, or they’ll reseed to plague you later on.

Check Plant Ties. Landscape plants are growing rapidly. Check plant ties at tree stakes and on vines. Loosen or remove them to prevent serious damage to trunks and stems.

Fertilize Lawns and Landscape Plants. The frequent irrigations, necessary in summer, wash nutrients (primarily nitrogen) out of plants' root zone. Plus the long, sun-filled days accelerates growth, causing plants to need extra nutrients now. Apply ammonium sulfate or similar high-nitrogen fertilizer monthly July through September. Fertilize citrus for the final time this year no later than early September. A fall application produces new tender growth that's more susceptible to frost damage.

Move Container Plants. If your container plants are mobile, give them a vacation from the long, intense hours of sunshine and move to dappled shade beneath trees, or to an eastern (morning sun only) exposure.

Cut Back Tomato Plants. The summer sun has probably taken a toll on your tomato plants. Cutting them back July-August results in fresh new growth with fresh new flowers, and with some luck, a new crop of tomatoes by fall.

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Last modified 06/24/2023