Are Wrapped Trees Warmer in Winter?

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Robert Pavlis

In a previous post I discussed wrapping a tree to keep it warm. I looked at the physics and concluded that wrapping a tree, or any  other plant, does not keep it warm. I had never seen any data to support this position, but it certainly follows basic laws of physics. I decided that this winter I would measure the temperature under a wrapped evergreen.

Wrapped trees stay warmer
Do wrapped trees stay warmer? Photo by Robert Pavlis

The Experiment

I have a yew that the deer eat every winter unless I wrap it. So I decided to use this tree as my test subject. It is located near the house, on the northwest side. The tree is wrapped in several layers of burlap down to about 6 inches from the ground. During the winter I went out with a lab grade thermometer to measure the temperature both in the air and under the burlap wrap.

I tested this on cool days, sunny days, cloudy days, windy days and even on our record breaking -30 C day.

The temperature of the air under the wrap and outside the wrap were exactly the same under all of these conditions. It is good to know that the laws of physics still hold true!

Food Science for Gardeners, by Robert Pavlis

What About the Wind Chill Factor?

The wind chill factor is something we humans use to express how we feel. On a windy day, we feel colder because the wind is removing body heat from us.

In winter, plants have almost no body heat. The temperature of the plant is the same as the air temperature. Wind does not decrease the temperature of the air or the plant.

The wind chill factor has nothing to do with plants.

Are Wrapped Trees Warmer?

Wrapping trees will not keep them warm. The wrapping may reduce moisture loss which can be beneficial in some cases–this is discussed in more detail in Should Plants be Wrapped in Winter.

Do Styrofoam rose cones work? Find out in a new post called Styrofoam Cones – Do They Keep Roses Warm in Winter?

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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

9 thoughts on “Are Wrapped Trees Warmer in Winter?”

  1. I’m glad you did this test. I’ve always suspected we anthropomorphize plants a bit… because we bundle up in winter, we think putting a sweater on a tree will keep it warm. Thanks for uncovering the truth. 😎

  2. I’ve done the same experiment but in a poly tunnel. Even with lots of mass to warm up in the day and release warmth later the poly tunnel temp still drops to the same as outside. The only difference is the speed of change.

    Wrapping a tree would be the same. Any trapped heat under the wrap would dissipate very quickly simply because there wouldn’t be much of it.

    I’ve always thought the wrapping of a tree or poly tunnel was simply the act of stopping (or reducing) the moisture from freezing directly on the sensitive parts of the plant. Snow or frost forms on the wrap or poly tunnel cover far more than on the actual plant.

    Any freezing under the wrap would be defrosted quicker also simply because there is physically less frozen moisture.

    Sap rises in the spring within trees, which also tells you that there is a lack of moisture within the tree during winter. Lack of moisture is less freezing, less freezing is less cell damage due to expansion of the moisture within the cell.

  3. I will try wrapping my two tiny fig trees with several layers of corn stalks+one layer of burlap. Will check the temperatures to see for myself, my neighbour has had a fig for a couple of years,and he says it keeps dying back every winter regardless of how he wraps it.

    • I’d be interested in seeing your results. Measure the temperature both inside the wrapped area and outside. Measure in the shade so the sun does not affect the temperature of the thermometer–just block the sun with your body. You will need a fairly accurate thermometer to see any difference.

  4. Where tree wrap can help in winter months is to *assist* in protecting the tree trunk from extreme temperature swings, which the trunk would be exposed to when allowed to warm up in direct sunlight during the day, followed by severe drop in temperature over night. In this case, the tree wrap isn’t keeping the tree warmer, but rather, moderating the temperature change.

  5. I think you might be glossing over wind chill too much. When the temperature drops, and is accompanied by wind, the temperature within the wrap–and of the tree–will drop more quickly than when no wind is involved.

    The question then is: does it matter how quickly the temperature changes? Or more specifically, can wind cause enough change in the rate of temperature change of the tree that the tree is harmed, when it would not have been harmed without the wind?

    • One of the tests I did was to measure the temperature on a very windy day. I expected to see the temperature under the burlap a bit warmer, but that is not what I found. I also measured the temperature with the thermometer held up in the wind and behind some shelter and there was no measurable difference in temperature.

      Trees in winter are giving off virtually no body heat. That means they are at the same temperature as the surrounding air. As the air temperature drops, so does the temperature of the plant. You are correct that if the air temperature drops very quickly, the temperature inside the plant takes a bit of time to drop. Wood is a good insulator. But that will happen the same with or without a burlap wrap.

      • I think you are right, though as a very technical matter the appropriate test would be to measure the rate of temperature drop under the burlap and outside, specifically at the onset of the change in weather that includes wind–as compared to temperature drops that are not accompanied by wind. In all likelihood, the results would be the same as what you’ve already found, or close enough to not matter.


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