August in Arizona is the time when we all begin to wonder when the summer will end. Unfortunately, we have about two months left to endure. Monsoons clouds are beginning to build, the humidity is soaring and a few raindrops are falling.
This month you will notice that your succulent plants are succumbing to high nighttime temperatures. When the night temperatures stay at 90º F or above and the humidity is high, most succulent plants can’t breathe. After several nights in a row, chances are many of them will rot. Other than careful watering, there is nothing that can be done.
Birds are in abundance and many will re-nest if we have good monsoonal rains. All manner of wildlife are more active now, especially in the evening: snakes, owls, nightjars, ground squirrels, scorpions. Once in awhile an unusual bird species will be blown off course by monsoonal storm winds.
Watch the rain activity around your landscape. Note the runoff direction, where the puddles form, and areas of erosion. Why? This will help you re-contour your yard for more efficient water harvesting.
Keep note of the sun’s position in the sky. As the month progresses and the angle changes, you may begin to notice side-burning on plants, particularly cacti and succulents. Add small pieces of shade cloth until the days cool off.
Look for flowers on your Texas Rangers (Leucophyllum spp.) after rainstorms. Also blooming are Tecoma spp., Guayacàn (Guaiacum coulteri), Desert-willow (Chilopsis linearis), Little-leaf Cordia (Cordia parvifolia), rain lilies (Zephyranthes spp.), Sacred Datura (Datura wrightii), and Baja Fairy Duster (Calliandra californica). The Desert Hackberry (Celtis pallida) will be full of fruit. Leave them for the birds and other wildlife. Same with the prickly-pear cacti – let the fruit ripen and be eaten.
Monsoons bring humidity and moisture to the low desert. More and more we see periods of high night temperatures of 90º F and above during this time. This makes it a risky month for watering cacti and some other succulents, particularly aloes. Be sure to adjust your irrigation timers if we receive a good soaking rain. Mediterranean plants and California chaparral plants, such as Cleveland Sage and White Sage (Salvia clevelandii and Salvia apiana) can be easy to overwater during this time. Pay special attention to your container plants, particularly if they are herbaceous in nature as they may need watering every day.
What to Plant
Although fall is the better time, with the higher humidity we can get away with planting trees and shrubs now but not perennials. Monsoon crops such as cowpeas, tepary beans, Hopi red-dye amaranth, Devil’s claw and small gourds can be started. If you have tomatoes, cut them back; if you don’t, plant now if they can be provided some shade. Cabbage, broccoli and cauliflower can all be started indoors from seed for fall planting.
The extra humidity will elicit new growth on trees and shrubs. Minimal pruning should be performed during this month. Remove dead or broken branches and repair storm damaged areas but do not open up the canopy just yet.
Vegetables and herbs can be mulched this month. This is also a good time to fertilize your container plants.
This month you’ll see an abundance of insect activity. Mosquitoes are now commonplace throughout the Valley. Be sure to empty any containers, buckets, bowls, etc. that might catch rainwater as the larvae require water in which to mature. Cicadas are still buzzing away at this time and twig damage may be evident from their egg-laying. Ants and termites are swarming and if you see the mud tunnels of termites crawling up your plant stems, just wash them off. They are not harming the plants. Cochineal scale, that cottony substance all over your prickly-pears may also be active now. Wash them off with a hard spray of water or use insecticidal soap. Powdery mildew may also be showing up on your penstemons due to overwatering.
Grasshoppers and aphids will show their presence too. The excrement from the aphids may cause sooty mold, especially on the Desert Milkweed (Asclepias subulata) and penstemons. They can be discouraged with a spray of water or insecticidal soap, but there really isn’t much you can do about them. Root borers are active and they’ll emerge around your trees’ drip lines but again, there isn’t much that can be done about them.
Many butterfly and moth species are in abundance this month, particularly the Gulf Fritillary and the Hawkmoth. You’ll see the caterpillar larvae on certain plants but, unless the damage is significant, leave them to become the next generation of butterflies.