In winter there is much more variation in temperatures in the areas called “deserts” in the Southwest–the areas where annual rainfall is low. Winter in Phoenix gives gardeners a break from those 110F daytime highs of summer. The average daytime high in Phoenix in winter is 68F and in Palm Springs it’s 72F. The average daytime winter high in Las Vegas is 58F and in El Paso it’s 59F. That sounds like good news for desert gardens — right?
But that’s only part of the story. Then there are the winter nighttime lows. If you live in central Phoenix or Palm Springs your garden will not be frost-bitten in winters. You can safely garden without worry, 12 months of the year. (Phoenix suburbs and other towns in the desert southwest at higher elevations may end up with overnight freezing temperatures, so watch your local weather report.)
Gardeners in Las Vegas, however, will have about 24 days of overnight winter frost. And dry El Paso? Wow–gardens there are enduring overnight frost as many as 75 times a year. So here are some tips about winterizing those gardens.
Tip 1: Protect against frost
Cover tender plants with frost cloths, burlap, or old sheets. Avoid plastic, which traps moisture and causes damage. Anchor coverings to the ground to trap soil warmth. Prioritize protection for citrus trees, succulents, and young ornamentals.
Tip 2: Know your plants’ limits
Not all desert plants are equally hardy. Many cacti, including the very popular Barrell Cactus, will tolerate a light frost, but suffer under prolonged hours of freezing temperatures. Prickly pear and saguaro are hardy, if they are not water-logged from too much irrigation.
Succulents, like aloe, are tougher, while others, like echeveria, are delicate. And it almost goes without saying, but I will say it anyway: non-native plants, including shrubs and trees, are especially vulnerable and can be damaged by night freezes. For example, my favorite palm tree, the Queen Palm, (Syagrus romanzoffiana) hates cold weather so I was unable to plant it safely in Las Vegas. It would have not survived the first cold winter there.
If you have plants in containers that are sensitive to freezing temperatures, bring them indoors or tuck into a sheltered patio.
Tip 3: Adjust your watering schedule
Cooler temperatures and fewer hours of sunlight mean slower evaporation so reduce watering frequency and duration to prevent root rot. Dormant plants need little to no water, while winter vegetables and annuals still require light irrigation. Pro Tip: Water before a freeze—moist soil holds heat better than dry soil.
Tip 4: Plant cool-season veggies and flowers
Desert winters are perfect for growing leafy greens, carrots, peas, potatoes, and broccoli–particularly in raised beds. If your heart is set on flowers you can get seasonal color in winter with nasturtiums, lupines, poppies and snapdragons. They are best planted in a sheltered area. And companion planting helps maximize space and protect soil during cooler months. (More about companion planting in a future post, including wisdom from indigenous people.)
Tip 5: Mulch and enrich the soil
This is desert gardening 101: mulch, mulch and mulch some more. Moderately coarse organic mulch is the best because it performs two tasks: 1) heaped around plants it is a physical barrier insulating against summer heat, winter frost and evaporation and 2) as it decomposes gradually over time organic mulch helps balance the soil’s pH and provides nutrients to your plants.
We do not recommend using rock mulch close to plants. Rock mulch can heat up to 150 degrees Fahrenheit in direct summer sun and that will kill the plant.
And, finally, while you are working in your garden, check the drainage. Winter rains, like our summer monsoons, can clog natural flowing water paths and the water can pool and damage roots.
Happy gardening!
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