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August/September 2023 Garden Checklist and Solutions

All Elevations

Monsoon season is a great time to plant native flora that thrive in local microclimates and depend on summer rains to germinate and survive. Find a variety of mixtures—as well as more specific seed packs—free of charge through local seed libraries, or for purchase through websites such as Native Seeds/SEARCH ( and at local nurseries. Prepare the ground by raking to create areas for the seeds to settle, which will prevent them from blowing or washing away or from being eaten by birds. This is also a good time to think about what to plant once the weather cools off. Map out your landscape to see what opportunities exist for new plantings or by moving existing plants to locations where they would be more suitable. Be sure to consider the mature size of plants to ensure they will not be too crowded in your garden.

Pruning is recommended for many types of plants. Timing is essential to avoid stressing plants more than necessary, and you don’t want to prune off flower buds before enjoying the blooms. The amount of pruning on individual plants is also important. Some shrubs, for example, can handle renovation pruning down to 18 inches tall every three years, but some other plants will die if cut back severely. In general, don’t take off more than 25% of the green parts at one time so the plant still has a chance to photosynthesize and grow with minimal stress. If you are unsure when or what is best, ask reliable sources, such as nursery professionals, where you buy your plants, the University of Arizona Cooperative Extension (, or a nearby state such as New Mexico, Colorado, Utah, Nevada or California. 

Selective pruning—cutting some branches back to the point of attachment and leaving the rest as is—retains the general shape of the shrub but can also open up the canopy to let more sunlight and air into the center, allowing the inner part of the plant to continue to produce leaves. The easier method of shearing plants is more common because it takes less effort. It is worth the extra work to use the selective method for the health of the plants. It also makes the shape more natural and attractive than the cylindrical or rounded shapes that often result from shearing.

Irrigation needs may vary based on precipitation. Local weather can be monitored through online resources such as to determine how much rain has accumulated in your area. Monsoon rains may reduce the need for irrigation but probably not enough to turn it off for the whole season. Keep an eye on your plants to determine irrigation needs. Curling or dropped leaves or a yellowish appearance can be symptoms of drought. A soil probe can also help determine moisture below the surface.

Continue to monitor weeds regularly. Hoe before weeds become large and tough. Using the tool can sever the unwanted plants at ground level or even pull them out by the roots if they are still young and loosely attached. Hoe a bit each day in the morning before temperatures are too hot to work comfortably. Know the symptoms of heat stroke and take precautions to stay safe.

Several years ago I discovered a blossoming vine growing all over a cactus in my yard. I pulled it all off, but it has since spread to walls and attached to my lantana. On a recent hike, I saw the same vine growing on a saguaro. It has a faint onion smell, is a little sticky and grows quickly. What is this plant, and what should I do?
Your vine is commonly known as climbing milkweed (Funastrum cynanchoides). It is native to the Mojave and Sonoran deserts and can be found from California to Texas, often in dry areas. Like other milkweeds, it has a milky sap. It flowers throughout the spring and summer and attracts butterflies such as monarchs. While climbing milkweed is sometimes seen as a nuisance, it doesn’t appear to harm other plants. Remove it if it bothers you, or let it grow, enjoy the butterflies that are drawn to it and clean it up when you prune your shrubs.

One of my prickly pears became riddled with black splotches. I suspect the problem is caused by a fungus. If so,  will treating the soil with a fungicide eliminate the problem?
Lesions on prickly pear may be caused by several pests or conditions, but the most common is known as Phyllosticta pad spot, or dry rot, which is very common in our area.  Because it is endemic to the desert, no amount of fungicide would be effective. Phyllosticta spreads by releasing spores that are transported by rain and wind. The best prevention is keeping your plants healthy by planting them in the right place and keeping them appropriately watered and fertilized. Research shows that healthy organisms are less susceptible to pests. In some cases, insects are drawn to plants that are suffering from environmental stress because the plants give off chemical cues. Severely infected pads or plants should be removed from your landscape.

Another option is to use an electric or gasoline-powered weeding tool sometimes called a string trimmer. Although these only cut off the above-ground parts, they can be quicker than a hoe and handle larger weeds. Spraying weeds is considered the last resort because there is a risk of injury to nearby desirable plants, especially on hot or windy days—and to the user if applied improperly.

By mid-summer, many insects are at peak population levels. Weekly checks of vegetables and other tender plants is important to catch problems before they are too far along. Keep in mind that most insects are either beneficial or simply not a problem. In fact, a diverse population of insects is a sign of a healthy ecosystem. If you’re not sure whether there is a problem, consult your local nursery or cooperative extension professional before taking action. Some insect problems may be solved by spraying the plants with a garden hose or using low-toxicity products such as insecticidal soap and horticultural oil.

Beneficial insects that feed on pests naturally occur in the environment. Understanding which local insects are beneficial is helpful. There are lists and photos available online but not all of them occur in Arizona. Some beneficial insects may be purchased at garden centers or online and released into gardens. Understanding which ones to purchase depends on the issue to be addressed.

Low to Middle Elevations

The dog days of summer can be brutally hot in the low and mid-deserts. Still, there are things to plant, especially if you hold out for September. For example, beets, broccoli and Brussels sprouts are fall-season vegetables to start in late summer into early fall. Also consider lettuces, leeks, kale, radishes, spinach and fall peas. If temperatures remain high when it is time to plant, consider starting vegetables indoors or under shade cloth until they are established and temperatures drop.

High Elevations

Fall peas can also be planted in higher elevations, along with leaf lettuce, cabbage, cauliflower and broccoli. In higher elevations, fewer options are available, with chances of frost coming anywhere between mid-September to mid-October. Take advantage of the early cooler temperatures by planting shrubs and trees once the summer heat has passed.

Illustration by Gary Hovland

Another option for fall planting during chilly weather is a device called a cold frame, essentially a portable greenhouse,  which can be used to extend the growing season by protecting plants from the elements, protecting them from frost while allowing sunlight to penetrate for photosynthesis. Check your local nursery for more information on purchasing and use.

Fall is typically an excellent time to plant or transplant trees and shrubs. Once the summer heat has passed, take advantage of the cooler temperatures by planting shrubs and trees before winter sets in and makes the ground too hard to dig. Now is the time to think about what and where to plant.

I recently saw red bugs and a transparent red sap on the new growth of my Texas mountain laurel. Are these insects beneficial? What should I do?
These red bugs (Lopidea major), aka sophora plant bug or mountain laurel bug, are relatively harmless. They will suck some sap and do minor aesthetic damage to the new growth for a short time in the spring. Lopidea major lay eggs directly on the plant but will not cause enough destruction to justify spending time and money managing them. Insecticidal soap is a potential low-toxicity solution that serves as an irritant for small soft-bodied nymphs. While it will not kill the adult bugs, it may disrupt their feeding activity. If the soap solution doesn’t work, try an organic pyrethroid product called Pyganic, which has some efficacy against this type of insect.

Plan Ahead

When planting shrubs or trees the first step is often choosing a location. While there are many types of plants, the available locations will narrow the selection process significantly due to the space available for the mature size and requirements for sunlight, irrigation and maintenance. In Arizona, sun exposure and irrigation needs are critical to plant survival and considering how to meet the needs of the plant is not something to think about after it is already in the ground. Maintenance is also important and sometimes forgotten until it is time to take action. Planning to make time for necessary fertilization, pruning, pest management and cleanup should help decide if a plant will provide the benefits that meet or exceed the cost of planting them.


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