Wed 16 Feb 2011
Written by Jeff
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One of the -odd things about living in the desert is that it can be the hottest of places and, at times, very cold. Plants need to be able to withstand a wide range of temperatures. Native plants generally don’t have too much trouble bouncing back from either extreme heat or cold.
Gardeners always want to push the envelope and so it is with gardening in the desert. There are a host of plants that have been introduced to add variety and color to the native plants in our landscapes and these are generally categorized as “desert adapted.”
They originate from other arid places in the world and can withstand heat and may be drought tolerant. The problem arises with the cold weather. Among the adapteds are those which can withstand cold temperatures to the low 30s or high 20s. Others, however, die back to the roots when the temperatures plunge.
To extend the life of a plant in cold weather, it has become a ritual in the Sonoran Desert to use frost blankets or other fabric covers which can maintain some of the heat the earth has stored during the warm days to protect the plants that are borderline cold-sensitive. Special fabric is marketed as frost cloth, but sheets, towels and other fabric-content material can be used.
Burlap is relatively heavy so that is avoided unless there is no other option and then care should be taken to keep the weight off of the plant itself. Plastic can actually harm the plants and is not recommended. If temperatures really plunge, some gardeners also use holiday lights under the frost protection to generate heat and buffer the more tender garden denizens.
In practice gardens can look very weird (almost spooky) when frost protection is used. The picture below is a photograph of our double purple datura (front) and Swan Hill olive tree in the back. While the plants survived the frost, the young olive tree did have some leaf drop and the datura never flowered again and was later pulled.
Another plant that survived, but sustained some damage was our “Little John” bottlebrush pictured here under the cloth:
Our ice plants on the outdoor tables we use to keep them out of the reach of Javelinas (read the article HERE) did very well and continued to bloom and survive. These plants were a bit lucky because they were protected by the courtyard and the wall against which they rested.
In the back of our yard we have we have a raised planter with pansies (background) which did real well. Pansies are more cold hardy than most of our plants. They put on quite a show after the temperatures warmed a bit. The planter in the foreground had a dracena and a coral bells. The coral bells survived, but the dracena which in most climates would be an indoor plant was toast (so to speak!).
Frost cloth is used by the professionals too. Desert Ridge Mall in Phoenix has wonderful plantings and quite an investment. You can see in the picture below, they covered their pansies, alyssum and other plants.
Here is another picture that shows an error in methodology. There should not be any gaps in the cloth because this allows cold air to get under the cloth and potentially cause damage.
You might have noticed in the photos of our landscape, we used rocks to keep the frost cloths tight to the ground and prevent the wind from disturbing the shelters.
You might be thinking: “What would happen if a frost-sensitive plant is not covered?” Well, here is an example. I forgot that our four year old natal plums should have been covered.
After they were zapped by the first frost, this is the damage they suffered.
We covered them after that (below), but the damaged branches will have to be trimmed in the spring.
Gardening on the Moon, www.gardeningonthemoon.com, originally published this post