Heat Wave Survival Tips for Desert Gardens

Extreme heat, sun, and wind are to be expected during the summer in the desert southwest. But sometimes, we experience even “worse than usual” conditions that further stress already stressed plants. Here are 10 tips for helping your plants survive the next heat wave.

A heat wave is a period of unusually hot weather when temperatures are significantly higher than the historical average. They usually last a few days. And they are a desert gardener’s worst nightmare. It’s frustrating to see your plants suffer because of a few extreme days.

Of course, the best way to get your plants through a heat wave is to make sure they are healthy and well-tended to before they are blasted by extreme heat. But there are some tips that can help your plants cope during a heat wave.

Note that some of these tips are overall “best practices” while others are temporary measures. And I’ve also included some long-term strategies that will ease the burden on both you and your plants going forward.

#1 Water: Timing Matters

It’s a given that you should be watering your desert landscape plants properly — the right frequency and adequately deep and wide.

Make sure that all your plants are optimally hydrated before the heat wave begins. This may mean deviating from your usual watering schedule. And feel free to water longer than usual, too. Horticulturist and author Noelle Johnson (aka Arizona Plant Lady) recommends watering twice as long as usual before a prolonged heat wave.

You also need to water your plants at the right time of day. The experts agree that watering early in the morning is best. Extreme heat interferes with a plant’s ability to take up water. Early morning watering allows the plants to take up water when they do so most efficiently.

Another timing tip is to split your watering sessions into two shorter cycles. This gives the water a chance to soak into the ground, since it tends to run off of dry, hardpan soil. For example, instead of watering a plant for 20 minutes, water it twice for 10 minutes with a short break in between.

Pro Tip!
Be sure all your plants are optimally
hydrated before the heat wave begins.

#2 Provide Shade (even if it’s ugly!)

You can’t outwater too much sun, although many gardeners try. Water isn’t the only thing plants need during a heat wave. They may need shade.

Shade new and sensitive plants. Don’t worry if it’s ugly, as long as it gets the job done!

Providing shade helps your plants survive a heat wave in two important ways.

First, it can prevent sun scald. The sun is so intense in the desert southwest that even cactus and agaves can get sunburned!

Sun scald can appear as dark, cracked bark on trees or bleached out patches on succulents. Depending on the species, leaves turn pale or have yellow or brown spots.

Second, providing shade is critical to keeping your plants’ roots cool. Whether your ground is covered with gravel, pavers, artificial turf, or organic mulch, they all get blazingly hot in the sun, up to around 160℉. This heat dries out the soil and can kill surface plant roots.

Did you know that most plant roots are located in the top foot of soil? Even the roots of saguaro cactus are largely found within the top 4 to 6 inches of soil.

You can provide large swathes of shade by covering an area of your yard with shade cloth or a shade sail. It reduces the intensity of the sun that hits your plants and the amount of moisture lost through the leaves. It also reduces evaporation from your soil and keeps your soil cooler.

You can make your covering as simple or as fancy as you’d like. You can temporarily shade a large plant or group of plants with a patio umbrella.

If you just need to cover a plant or two, you can use pieces of shade cloth, burlap, or any semi-sheer lightweight fabric.

Or you can strategically place a patio chair, small table, or basket to provide shade during the hottest part of the day.

There’s some evidence that misting shade cloth could temporarily cool your plants even more. This might be something to try over a vegetable garden.

While it’s normal to want to do something — anything! — to help your plants, sometimes the best thing you can do is to leave them alone. So the next four tips are things you should not do during a heat wave.

#3 Don’t Prune

Don’t prune your plants now. Even dead or partially dead leaves and branches continue to provide shade that keeps healthy foliage protected and plant roots cool.

#4 Don’t Fertilize

Don’t fertilize your plants now. I know some fertilizers and DIY remedies promise to deliver “stress relief” but don’t believe it. Fertilizing encourages new growth, which is highly susceptible to sun scald and heat damage.

And you don’t want to risk of fertilizer burn, which is more likely to happen during hot, dry, sunny weather.

#5 Don’t Spray

Now is not the time to spray your plants with anything other than water. Don’t spray plants with insecticides, fungicides, neem oil, insecticidal soap, dish soap, or any other home remedy (even if it’s “natural”).

If you find insect pests on your plants, hose them off with a jet spray of water instead. This should be your first line of defense against unwanted bugs any time of year, since sprays that kill insect pests kill beneficial bugs as well.

#6 Don’t Transplant

Sometimes you realize you’ve put a plant in a “less than ideal” location. As in, “I didn’t realize it would get that much sun there!” 🥵

If this has happened to you, you might be tempted to move a plant now, but please don’t. Transplanting during a heat wave will stress it even more. Do your best to protect your plant for now and transplant it during cooler weather, preferably in the fall.

#7 Give Your Plants a Shower

Plants have pores called stomata that regulate gas exchange. Plants “breathe” through their stomata — carbon dioxide moves in and oxygen is released.

Stomata open and close to release water vapor as part of a process called transpiration. Transpiration, among other things, helps to keep plants cool during hot weather.

Clogged stomata can reduce a plant’s ability to transpire and cool itself. Cleaning the dust away with an occasional spray from your hose will improve its ability to cool itself.

If the water coming out of your spigot is hot, use the “mist” setting of your hose nozzle. The fine water droplets will cool down before hitting your plants.

#8 Move Gravel Away From Plants

Depending on where you live, there may be a custom of covering yards with gravel. Or you may live in a community that requires its use, at least in your front yard.

But either way, you can at least move gravel away from its base by at least a few inches, so that it’s not touching the base of the plant.

Then you can add a ring of mulch or compost around the plant base. I prefer to top dress with compost, which adds organic matter and nutrients to the soil faster than wood chips.

Learn more about the benefits and drawbacks of gravel vs organic mulch here.

#9 Give Your Potted Plants Extra Care

Give your potted plants extra water during a heat wave since they dry out faster than plants in the ground. Annuals and other flowering plants may need water daily.

If you can, move them out of direct sun. If you can’t move them, provide them temporary shade however you can.

You can minimize heat stress going forward with your choice of pots:

• big (at least 20″ tall and wide) is better than small
• ceramic or plastic is better than terra cotta
• light colors are better than dark

Pots that fit this description retain moisture longer and keep plant roots cooler.

#10 Plan a Long Term Strategy

When the heat wave is over, assess the damage. Which plants came through unscathed? Which looks worse for wear? Did any die? You may want to replace them with more heat-resistant plants in the fall, which is the best time to plant most desert landscape plants.

It’s also a good time to assess how you can reduce the amount of hardscaping in your yard (which makes yards hotter) and how to add more plants (which makes your yard cooler). There is nothing that will make your yard more resilient to the next heat wave than a few strategically placed shade trees.

If adding more trees isn’t feasible, consider adding a shade sail, ramada, pergola, or any structure that will provide more shade, if your space and budget allow.

But every bit of shade helps. Even if you can only add a few ground covers, it can make a difference by shading and cooling the roots of nearby plants.

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