When night-time temperatures dip to freezing in the desert southwest, you might be wondering which, if any, of your landscape plants you should cover. Here’s a look at which plants may need protecting, and which don’t.
After months of struggling to keep plants alive in the heat and drought, it’s always a bit jarring to realize that some of your desert landscape plants might now succumb to the cold. 🥶
So when a cold snap comes, you might find yourself scrambling and haphazardly covering plants, hoping you’re protecting the plants that need it.
So it’s no surprise this leaves a lot of gardeners wondering…
- How cold does it need to get before I cover my plants?
- Which plants should I cover?
Not every plant in your yard will have the same requirements. Popular landscape plants’ cold tolerances can vary from showing damage in the relatively balmy 40s (as in the case of snail vine) to surviving sub-zero temperatures (blackfoot daisy survives to a frigid -20℉)!
When you are trying to decide whether to cover any particular plant, there are two things you need to know:
- How cold it is likely to get
- How cold hardy your plant is
Let’s look at these two variables in depth.
How Cold is it Going to Get?
Obviously, no one can accurately predict the weather — even the experts. But there are a few piece of information that will increase your likelihood of making the right call when it comes to covering your plants.
Know Your “Normal” Winter Weather
First, let’s look at the official coldest temperatures in Tucson and Phoenix for the last 5 years.
Tucson’s Coldest Days
| Date | °F |
| Jan. 9, 2024 | 28 |
| Jan. 26, 2023 | 27 |
| Feb. 3, 2022 | 26 |
| Dec. 18, 2021 | 30 |
| Feb. 5, 2020 | 24 |
Phoenix’s Coldest Days
| Date | °F |
| Jan. 5, 2024 | 35 |
| Feb. 16, 2023 | 35 |
| Dec. 17, 2022 | 36 |
| Jan. 25, 2021 | 36 |
| Feb. 5, 2020 | 35 |
You can see that it hasn’t officially dropped below the mid-twenties for the past 5 years in either city.
Knowing your area’s recent history gives you a general baseline as to what is “normal cold.” If your plants have survived the past few years without covering, there is no reason to start now, unless you are facing abnormal cold.
Not in Tucson or Phoenix? You can find the historic lows for your area at CurrentResults.com.
Get a Hyperlocal Forecast
When a cold front is headed your way, you need to accurately predict how cold it’s likely to get in your yard, not at the airport. It’s extremely helpful to follow a weather forecast as close to home as possible.
I use Weather Underground which offers over 60 weather stations in Tucson to choose from.
To find your nearest station, type your city or town in the search box, then click on “Change” and you’ll be presented with a drop-down list of “Nearby Weather Stations.” Review the map and choose the weather station nearest you.
Know Your Microclimates
The temperatures in your yard can vary greatly, so you also need to know how cold it’s likely to get in that plant’s microclimate. It’s not unusual to have temperature variations of 10 degrees or more in one yard.
I suggest putting a thermometer or two in various spots in your yard to track your microclimates. Seeing how consistently cooler or warmer some locations are can be enlightening. Knowing this can make the difference between having to cover a plant or not.
If you see a plant’s leaves turning red, purple, or black,
that’s a sign it’s experiencing cold stress.
How Cold Hardy is Your Plant?
The second variable you need to know is a plant’s cold hardiness.
Don’t assume that all your plants need cold protection. Most desert landscape plants are sufficiently cold hardy to withstand an occasional freeze, especially if they are native.
You can make life a lot easier for yourself if you only buy plants that are appropriate for your USDA hardiness zone.
Anytime you buy a plant, it should have a label that clearly states that plant’s cold hardiness zone. If it doesn’t, you can ask someone at the nursery or look it up on your phone before you make the purchase. (You’ll find zones and cold limits for over 100 common desert landscape plants in our Desert Plant Library.)
But to buy plants appropriate for your zone, you have to know your zone.
Zones were revised in 2023, and the new zones are very granular and can vary from neighborhood to neighborhood! So if you haven’t checked your zone lately, I suggest you confirm your zone by entering your zip code here.
There are a few other factors to consider.
Is your plant young or established? Young plants are more cold-sensitive than mature plants. A mature plant rarely needs protecting — if it’s made it this far, it should continue to be OK!
A good example of how cold hardiness can change over time is Lady slipper (Euphorbia lomelii). Young stems of this succulent can be damaged at around 30℉ while mature stems are cold-hardy to 25℉ and can withstand brief cold spells to 20℉.
Do you mind your plant having some cosmetic damage? There are many plants that survive freezing temperatures but will look a little worse for wear until new spring growth appears. So in this case, it’s a matter of personal preference whether you think it’s worth covering a plant.
Examples of plants that die back after the first freeze, but survive and rebound in the spring, include lantanas (trailing and shrub), cape honeysuckle, yellow bells, coral fountain, and queen’s wreath vine.
You can keep them looking better (and potentially flowering) if you cover, but they’ll be just fine if you don’t.
Do you cover your plants?
Or do “only the strong survive” in your yard? 😉
Please share your experiences in the comments below!
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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.
