It’s August in the desert southwest and we’re in the middle of the monsoon. Storms bring rain but also damaging winds. Here’s what tasks to do, pests to expect, and more.
August in the southwest garden is not much different than July. We’re still in the monsoon and the weather patterns are often similar. If you’ve had some rain, you may notice that wild areas, particularly the mountainsides, are greening up and summer wildflowers may even be in bloom.
August Weather Outlook
August is a mixed bag weather-wise for both you and your plants. The good news is that the average temperature drops a few degrees from July. However, the humidity continues to rise slightly (up 5% from July) and the average rainfall drops by half an inch.
Here’s a look at August weather averages in both Tucson and Phoenix:
August Weather Averages (Tucson)
| High temperature | 98°F |
| Low temperature | 74°F |
| Precipitation | 2.09″ |
| Relative humidity | 45% |
| UV index | 10.6 |
| Wind | 14 mph |
August Weather Averages (Phoenix)
| High temperature | 105°F |
| Low temperature | 83°F |
| Precipitation | 1.01″ |
| Relative humidity | 32% |
| UV index | 9.7 |
| Wind | 7 mph |
If you live elsewhere, enter your city or town in the search bar at TimeandDate.com to find your monthly averages. You can find your average UV index at UVIndex.io.
Common Garden Problems in August
Monsoon rains bring out more wildlife, some of which you may be delighted to see, and some, not so much. You’re likely to see more mammals, birds, snakes, toads, and insects.
Many human desert dwellers find the monsoon storms thrilling, but it’s not all roses for gardeners. Monsoon storms can bring flooding, hail, dust storms, and damaging wind. And an increase in moisture leads to an increase in insects and plant diseases.
What To Do in the Garden in August
August is a pretty quiet month in the garden task-wise. There’s not much to do except continue to keep your plants hydrated and watch for pests.
Watering
Once the rains come, adjust your watering schedule. You can skip the next scheduled watering any time you receive .5 inches of rain or more. I use a rain gauge to keep track of my rainfall. If you don’t have one, you can check out the rainfall map at the University of Arizona’s RainLog.org to see the rainfall totals nearest to you.
Not sure how to water your plants?
These articles can help:
How to Water Desert Trees: How Often? How Much?
How to Water Desert Shrubs: How Often? How Much?
Now is a good time to harvest rainwater. It doesn’t need to be anything fancy – simply collect it in whatever you have around that will hold water.
I have a rain barrel connected to a downspout, but I still set 5-gallon buckets around my roofline — you can never have too much rainwater! Then I cover them with snap-on lids to keep out mosquitoes.
If you experience a power outage, check your irrigation controller and reset it if needed.
If you are watering with a hose, always check the water temperature. Water from a hose can be hot enough to damage your plants.
Get Ready to Fertilize Your Citrus Trees
Citrus should be fertilized three times per year. Lemons and limes should be fertilized at the end of August or the beginning of September. This will be their third (and final) application for the year.
If you don’t have any citrus fertilizer on hand, it’s time to pick some up.
(Other citrus — oranges, tangerines, grapefruit — should not be fertilized now. They should have had their final application in the spring.)
Fertilizing instructions can be complicated. It depends on the size of your tree and the amount of nitrogen (N) in your fertilizer. To determine exactly how much fertilizer your trees need, see the University of Arizona’s Citrus Fertilization Chart for Arizona.
If your tree is one or two years old, there is no need to fertilize yet.
If You Have Storm Damage
Monsoon rains plus heavy winds are a recipe for storm damage. If your plants have experienced minor storm damage, remove any damaged or dead branches from trees or shrubs.
For more substantial damage, there are two kinds of help.
If you just need broken branches or a fallen tree cut and hauled away, it’s not hard to find this kind of help. There are many “landscapers” that can do this for you.
However, if you have a large cactus or tree that’s leaning precariously and you want to save it, call a cactus specialist or an arborist. They might be able to prune or reposition your plant before it’s too late.
Got branches?
Reid Park Zoo takes them to feed their animals.
Learn more about this program here.
Protect Plants From Heat Stress
After months of intense heat and sun, some plants, even cactus and succulents can show signs of stress from heat. While some may need more water, others just need relief from the sun.
Additionally, if you lost a tree or a large part of a tree, you may have plants that suddenly went from living in shade to living in full sun. This abrupt change can fry your plants.
You can provide temporary shade with shade cloth or for small plants, something as simple as a patio chair. If you have fallen branches, you can gently place them to temporarily cover plants. Patio umbrellas work great but don’t leave them up unattended. Sudden monsoon winds can knock them over or even turn them inside out.
Other Pruning Tasks
There are a few minor pruning tasks you can do in August. If you’re like me, you’re eager to tidy things up!
Native trees, especially palo verdes and mesquites can be pruned now with no problems. Heat-loving shrubs like oleander, red or yellow bird of paradise, or yellow bells can be lightly shaped.
Overgrown or leggy perennials and ground covers can be cut back by one-third to encourage new growth. Continue to deadhead spent flowers, especially those in containers, to encourage new blooms.
Garden Pests & Diseases
Continue to watch for insect infestations. Many insects are at their peak populations in August. Some common insect pests you may notice on your landscape plants this month include:
- ants
- aphids
- cochineal scale
- crickets
- spider mites
- white flies
Whiteflies and spider mites thrive in hot dry weather. If you see them on your plants, give them a spray with the jet setting of your hose.
Check around your yard for standing water which could harbor mosquitos. Empty pots, saucers, or any other forgotten nooks that hold water after rains. If you can’t empty them, add bits of mosquito dunks.
If you have a tree or shrub that suddenly and dramatically wilts but the leaves stay on the tree, it may have cotton or Texas root rot (Phymatotrichum omnivorum) which tends to show up this time of year. It is a serious, soil-born fungal disease that has no cure. The only recourse is to remove the plant and avoid planting another susceptible plant in that spot.
If you have vincas, also known as periwinkle, (Catharanthus roseus) that wilt, but don’t recover from watering, pull them up and toss them. They are almost certainly infected by an untreatable, contagious soil fungus known as vinca wilt.
Weeds & Wildflowers
If the monsoon has brought you rain, you may find new weeds popping up in your yard. Try to pull them as soon as they appear since weeds are easiest to pull when the ground is saturated.
Early summer was a good time to sow monsoon wildflower seeds. If you did, some should be sprouted and blooming such as Arizona poppy.
Should You Plant in August?
While some landscape plants can be planted now (i.e., cactus, other succulents, native perennials), be prepared to spend more time and energy than usual watering and protecting them from the sun, pests, and wildlife. Most landscape plants will be much happier when planted in the fall and they’ll be less work for you, too.
Fun Gardening Events in August
August is the time to start thinking about what you want to plant in the fall. If you are considering a new tree and live in Tucson, you might want to check out the Trees for You Program.
Every fall TEP (Tucson Electric Power) customers have the opportunity to buy two 5-gallon trees for $5 each. The first day to order in 2024 is September 3.
Besides taking care of your gardening tasks, there are plenty of other ways you can keep growing and learning about gardening. There are ongoing gardening classes and activities in person and online.
You’ll find a list of gardening-related events in our Tucson Gardening Events Calendar.
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Author Bio
Deane Alban is the creator of Southwest Gardener. She is a science writer with a bachelor’s degree in botany from the University of South Florida. Gardening is her lifelong passion. She’s been gardening in Tucson for 15 years.
