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January 13, 2014

DESERT BLOOM: Freezing Temps



When people hear the term “desert”, they often imagine an intensely hot, dry area, but I’d say those dramatically cold temperatures that recently seized Southern Nevada clearly demonstrated otherwise. When an area’s a desert, you can be certain only that the environment is dry, but it’s not necessarily hot.  Antarctica, for instance, is technically the largest desert on the planet. Southern Nevada might have felt like an ice box, but it couldn’t compare with that!

For some local landscape plants, ‘though, the weather might as well have been arctic.  Since freezing temperatures are relatively uncommon in the Las Vegas valley and its environs, it can be tempting to risk using plants that aren’t well suited for the extreme conditions here. 

When temperatures are lower than 40 degrees, the most tender plants can develop something called “chilling injury”.  These are varieties that aren’t well adapted to this area; they’d survive better in regions further south, like the Sonora Desert of southern Arizona. 

A lot of the specimens that’re widely planted aren’t quite that fragile, but they’re not exactly “hardy” either.  They may not suffer chilling injury, but they can’t tolerate freezing temperatures. They’re definitely going to experience harm on those rare occasions when it drops much below 30º.  It’s a pity to see the damage that’s occurred in local landscapes already, and it’s going to be more pronounced by the end of winter.

Oleander with frost damageMarginal plants can be killed in the desert cold; but even some of our most reliable ones can be damaged.  Oleander, for instance; it’s tough. It can tolerate our conditions very well, most of the time. Even in the hottest summer sun, it’ll thrive and flower merrily. When temperatures stay well below freezing for several nights in a row, the leaves’ll become damaged and might appear to be diseased. The root system may be perfectly OK, but above ground, it looks pretty forlorn.  Fortunately, when the shrub produces new foliage in the spring, it’ll more than likely look fine.

We all try to skirt around Mother Nature; including those of us who should know better.

I’ve had a lovely grouping of large aloe vera (that’s Aloe barbadensis) growing in my yard, and these plants were terrifically successful when we had mild winters for their first few years. Being from Africa, however, they’re neither native, nor terribly well adapted. 

Aloe Vera with Frost DamageAfter a week of evenings and nights in the deep freeze, some of them have become flaccid and grey, as they’ve done in other bad winters.  Because they were well established before the cold, the root system endured, and that will allow them to revive. I’ll have to remove the mushy center of the plants, so they don’t rot in the ground. There are probably thousands of local gardeners facing a similar situation – healthy plants that survived previous winters but now look like death.

At the Cooperative Extension office, we want to hear about these plants.  Specifically, we’d like to know:

What kind of plant it was, and how long was it in its location. Was it protected by a wall or exposed to the wind? What direction did it face?

It’s also important to know if it was healthy before the freeze, properly watered and fertilized.

We’ll use this information to develop guidance for people, so there’ll be less of this heartache in future winters.

Happily, a plant may look as if it’s dead, but as long as it has a robust root system there’s a fair chance that it has survived and will return.  If you can avoid removing it until well into the spring, you might have a happy surprise.

For the rest of this winter, try protecting that root system by keeping mulch on the soil.  A layer of bark, chipped wood, or even straw helps moderate soil temperatures, and that can make a difference in plant survival.

Let me remind you - I’ll be offering an expanded “Growing in Small Places” series in 2014, with the first class on Pruning in January. Call the Master Gardener Help Line for details.

For KNPR’s Desert Bloom, this is Dr. Angela O’Callaghan of the University of Nevada Cooperative Extension.

See discussion rules.


AngelaFeb 19, 2015 | Tricky Spring
If you're thinking that our warm weather means your plants are safe from a late frost, you're probably right. But then again, you never know. It only seems that Jack Frost has skipped a visit to Southern Nevada this year. Here's Angela O'Callaghan with Desert Bloom.

NormFeb 14, 2015 | Selective Pruning
Norm Schilling guides gardeners to keep up as Spring approaches. Selective pruning will keep things on track in the yard.

NormJan 21, 2015 | Prepare for Spring Now
Don't look at the calendar. Look at your plants to tell you what do to in the yard right now. Your plants think Spring is near, so use this time to transplant and prune. Desert Gardener Norm Schilling tells us what to look for.

NormDec 30, 2014 | Winter and Citrus
Citrus can thrive in Southern Nevada - even in our cold - when you choose the right varieties. Norm Schilling tells us how.

AngelaDec 13, 2014 | To Prune or Not to Prune
As winter draws near, leaves begin to fall. And the bare view may prompt some excessive pruning. It's tempting, but your plants may appreciate a little restraint. Here's Angela O'Callaghan with Desert Bloom.

NormDec 6, 2014 | Prepare Your Plants for Cold Weather
It's not cold . . . yet, but Norm says be ready and your yard will appreciate it. Don't let a cold snap cost you your investment in plants in your yard. Norm Schilling has some ideas to get ready.

AngelaNov 25, 2014 | Evergreens
As we head into the holiday season, more attention is given to 'evergreens.' Too many cones on a pine tree might be a sign of weakness. Angela O'Callaghan tells us all about evergreens on Desert Bloom.

NormNov 14, 2014 | Fall Colors
Even in the desert, Fall colors can brighten your landscape. Here's Norm Schilling with Desert Bloom.

NormOct 28, 2014 | Fall Colors - Web Only Edition
With glorious weather for our yards to fall back into bloom, Norm has some additional suggestions for color to add to the profusion of blooms for this time of year. (Web-only content)

NormOct 7, 2014 | Second Spring
The call it a "second spring" Norm Schilling has some plan ideas to make Fall colorful in your yard. He has a checklist of plants looking their best, because now is the time to plant in Southern Nevada.

AngelaSep 30, 2014 | Fountain Grass
A weed by any other name is still a weed even if it doesn't look like one. If only everything in our gardens thrived as well as weeds. Here is Angela O'Callaghan.

NormSep 15, 2014 | Desert Heat
Norm describes a significant casualty of the desert heat. There's going to be a big gap in Norm's Yard and a lesson on the reality of our desert landscape.

AngelaAug 12, 2014 | Organic Pesticides
Choosing a method for ridding your garden of an unwanted guest, be it bug or weed, is not always a simple choice. But the more you know, the better it goes. Here's Angela O'Callaghan

NormJul 28, 2014 | Lose that Lawn
We know, it's a desert out there including every place there's a lawn. Norm Schilling reminds us all the ways he wants you to consider losing the lawn... permanently.

AngelaJul 14, 2014 | Protect Fruit Trees from Birds
If you put a good deal of care into growing fruit trees, there are likely some birds who will take advantage of your effort. Here's Angela O'Callaghan.

NormJul 10, 2014 | Palm Care, Part 2
To keep, or not to keep. Norm Schilling ponders his palm trees, on this edition of Desert Bloom.

NormJun 10, 2014 | Palm Care
Norm Schilling has mixed feelings about how we use Palms in our yards. Full grown palm trees transplanted into the entry way of a mall is a common sight that tells Southern Nevadan's "something" is nearly open for business. He reminds us that those palms come with challenges.

AngelaJun 3, 2014 | Hot Weather Plants
As temperatures across the Valley begin to climb, you might be wondering what will survive in your garden in the months ahead and what probably won't. There are some 'sweet' options. Here's Angela O'Callaghan

NormMay 20, 2014 | Desert Color
Norm Schilling just got back from Belize and has some ideas for lush leaves in your desert yard. He reflects on some well suited plants to provide color and variety in this edition of Desert Bloom.

AngelaMay 6, 2014 | Emerald Ash Borer
Raising a healthy shade tree in the Mojave is not always easy. And if one particular insect makes its way here, it could get even harder. Here's Angela O'Callaghan with Desert Bloom.

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