July: What to Do in the Desert Garden

In the desert southwest, July means the arrival of monsoon storms, which bring higher humidity and much-needed rain. Discover what you should and shouldn’t do in the garden this month, and things to watch out for during this changeable month.

July in the southwest garden is a month of changes. The monsoon officially begins June 15, but the first rains usually arrive in early July.

You may or may not find the monsoon season thrilling. (I’m one of those desert dwellers who loves this time of year.) Monsoon storms bring welcome rainfall, humidity, and cloud cover — all a great relief for your plants.

But it’s not all good news for gardeners. Monsoon storms can bring flooding, hail, dust storms, and damaging wind. And an increase in moisture leads to more insect pests, plant diseases, and weeds. And some years the monsoon is a “nonsoon” that brings the wind but very little rain.

All these changes mean there are changes in gardening tasks this month, as well.

July Weather Outlook

While the average temperature doesn’t change much from June to July, the average humidity and rainfall increase considerably. This may feel less comfortable for you, but your plants will love it!

Here’s a look at July weather averages in both Tucson and Phoenix.

July Weather Averages (Tucson)

High temperature	100°F
Low temperature	75°F
Precipitation	2.45″
Relative humidity	40%
UV Index	11.2
Wind	15 mph

July Weather Averages (Phoenix)

High temperature	107°F
Low temperature	84°F
Precipitation	.98″
Relative humidity	27%
UV Index	10.3
Wind	8 mph

If you live elsewhere, enter your city or town in the search bar at TimeandDate.com to find your weather averages. And you can find your average UV index at UVIndex.io.

What To Do in the Garden in July

July is a pretty quiet month in the garden since it’s not time to plant, prune, or fertilize. However, you need to continue to keep your plants hydrated, protect them from too much sun, and watch for pests.

Continue to be prepared for heat waves and be ready for storms and subsequent storm damage.

Here’s a snapshot of the activities you can do this month and those you should stop doing.

✅	Sow summer wildflower seeds
✅	Water!
✅	Fertilize potted plants
✅	Watch for iron chlorosis
✅	Watch for pests, weeds
✅	Prepare for storms
❌	Don’t plant most plants
❌	Don’t prune most plants
❌	Don’t fertilize most plants

Read on for all the details and exceptions!

What You Can Plant in July

July is not a good time to plant desert landscape plants. Most plants will be much happier when planted in the fall, and there will be less work and worry for you, too. I find nursing new plants through the summer to be a stress I’d rather avoid. 😬

Some landscape professionals contend that during the monsoon, with its rain and higher humidity, is a good time to plant native and deciduous trees, palms, and summer flowering shrubs such as Texas ranger or lantana. However, I consider this a gamble since some years the monsoon is a dud that brings very little rain.

Heat-loving cactus and succulents can be planted or transplanted now, but it’s not ideal. If you do, cover them with shade cloth for the duration of the summer to prevent sun scald, especially if they are from a nursery or you don’t know their current orientation.

But if you get the urge to grow something new, sow some summer wildflower seeds, which germinate in response to the monsoon rains. Try to get them in the ground before the rains begin.

These plants grow fast and will bloom this summer. Here are some places that sell and ship desert wildflower seeds, including “monsoon seed mixes” which contain favorites such as Arizona poppy, blanket flower, and desert zinnia.

You can also start sunflowers from seed now. You can choose between growing wild sunflowers or one of the myriad of sunflower cultivars.

Summer Watering Tips

You can continue to water on the same schedule that you used in June. However, when (if?) the summer rains come, you can skip the next scheduled watering any time you receive .5 inches of rain or more.

Having a rain gauge is invaluable for keeping track of your rainfall. I’ve tried many types of rain gauges throughout my decades of gardening. Glass and plastic will crack from freezes (uncommon) or hail (common). I now have this silicone rain gauge, which has held up to all types of weather, including severe hail storms.

If you don’t have a rain gauge, you can check rainfall totals near you at the University of Arizona’s RainLog.org. This is especially helpful if you live around Tucson, where most of the data is collected, and somewhat helpful if you live elsewhere in Arizona. If you live in Maricopa County, check out the county’s Rainfall Data page.

For more help on how to water your plants in July,
check out our Desert Watering Resources.

Most potted annuals need watering daily. If you’re watering any plant with a hose, always check the water temperature first. Water from a hose can be hot enough to damage your plants, especially if you water later in the day. Assured cool water is one of the many reasons the best time of day to water is in the morning.

And while you’ve got your hose out, if you haven’t had any rain for a while, give your plants a quick shower to remove pore-clogging dust and prevent dust-loving spider mites.

If you haven’t already done so, give your irrigation system a good once-over. This is especially important if you travel during the summer. Irrigation system problems tend to crop up when you go out of town — ask me how I know this.

With monsoon storms come power outages. If you experience a power outage, check your irrigation controller and reset if needed.

Besides collecting water in my rain barrel, once the humidity goes up, I also collect AC condensate, an overlooked source of free “grey water.” Learn more about collecting and using AC condensate water here.

What to Fertilize

Desert landscape plants should not be fertilized in July. It further stresses plants by encouraging new growth, which is easily burned by the intense summer sun.

The exception is potted plants. Most potted plants benefit from a dilute solution of fertilizer every two weeks during the summer.

Watch for Iron Chlorosis

Iron deficiency sometimes shows up in the summer. The telltale sign of iron chlorosis is yellow leaves with distinctly green veins.

Desert soils contain iron, but it’s in a form that some plants can’t use, leading to deficiency. Iron chlorosis is especially common in non-native plants such as citrus, hibiscus, bottlebrush, and gardenia. (Native plants have developed ways to absorb the iron they need from alkaline soils.)

If you have any plants showing signs of iron chlorosis, now is a good time to treat them. Learn how in this article: Why Desert Plants Get Iron Chlorosis (& what to do).

What to Prune

While it’s OK to remove any damaged branches from trees and shrubs, July generally is not a good time to prune. Pruning further stresses your plants by exposing new areas to the sun and stimulating new growth.

However, it’s not a bad time to prune native trees such as mesquites and palo verdes. They may drop some sap but heal quickly during the hot weather. If you have trees with heavy canopies and you are concerned about storm damage, please have an arborist trim your trees — not a guy with a truck and a chainsaw.

Deadheading spent flowers, especially annuals in potted plants, encourages new flowers and is a “nice but not necessary” activity in summer heat. Don’t feel obligated if you’d rather not work in the heat.

Watch for Garden Pests

An increase in moisture leads to an increase in insects, plant diseases, and weeds. Watch for insect infestations on plants. Plants that have been stressed by heat and drought, or that have been overwatered, are more likely to harbor insect pests.

Some of the most common insect pests you may notice on your landscape plants this month include:

• ants
• aphids
• cochineal
• crickets
• hornworms
• leafroller moth caterpillars
• mosquitoes
• palo verde borers
• spider mites

Check around your yard for standing water that could harbor mosquitoes. Empty any pots, saucers, buckets, or any other forgotten nooks that hold water after rains. If you have standing water you can’t empty, add mosquito bits which kill their larvae. If you collect rainwater, keep it covered.

July showers bring… weeds!
Pull weeds as soon as they appear.
New weeds are easy to pull when the ground is wet.

If you notice a cochineal scale infestation on your prickly pear cactus, hit it with a hard spray of water. That should be all you need to do to get it under control.

Yellow bells (Tecoma stans) and its hybrids (i.e., ‘Orange Jubilee’, ‘Bells of Fire’, ‘Sparky’) are subject to damage from Tecoma leafroller moth caterpillars (Antigastra catalaunalis) which skeletonize the leaves. If you have an otherwise healthy plant, consider co-existing with them. They turn into moths that are important pollinators and food source for other wildlife. The damage they cause is temporary and only cosmetic.

If you feel they are overwhelming your shrub, prune off the worst areas or use the jet spray on your hose to dislodge them. Spraying insecticides, soap, or Bt (Bacillus thuringiensis) is largely ineffective since the caterpillars are tightly wrapped in leaves and protective webbing.

Upcoming Gardening Events in July

While the number of outdoor garden events tapers off in July, there are still numerous gardening classes and activities to attend, many of which are online. There is always something new to learn about gardening!

You’ll find an up-to-date list of gardening-related events in our Tucson Gardening Event Guide.

If you live in Tucson, be sure to check out these ongoing evening events now through August. (You may have similar festivities near you.)

• Tohono Chul’s “Chillin’ at the Chul”
• Arizona-Sonora Desert Museum’s “Cool Summer Nights”
• Tucson Botanical Garden’s “$5 Fridays”

Don’t live in Tucson? Look for online classes. You can participate in these no matter where you live.

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Photo Credits

Miwasatoshi, CC BY-SA 4.0, Wikimedia Commons

Arizona State University’s Virtual Library of Phoenix Landscape Plants