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Do Trees Hibernate?

Trees are a telltale sign of the change in seasons. Your tree is in bloom? Spring has sprung! Bare branches? Winter weather has arrived. You get the picture. The changes trees make throughout the year are extreme and help us understand how to better care for our trees no matter the season. For example, when the leaves fall off and the branches are left bare, our trees are telling us they’re changing and need something different. Why do the leaves fall off? Do trees hibernate? Do they need care if the leaves are all gone? Here is a look at what your tree is telling you when the cold seasons come.

Do Trees Hibernate?

To answer this, let’s take a quick look at what hibernation actually is. True hibernation requires a lowered body temperature, slower heart rate, and reduced metabolism. A tree obviously doesn’t fit that definition. Hibernation, however, is a type of dormancy, and there are many types of dormancy.

So do trees hibernate? Not exactly. It really comes down to technical terms. Some people will call a tree’s dormant state hibernation, but trees officially are entering a dormant state. Just like the animals that go into hibernation because of frigid cold and lack of food, though, trees enter dormancy when there is less light and temperatures drop to freezing.

Tree Dormancy

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To put it simply, dormancy is just a period of time when a tree slows down or is inactive. Like animals, there are some trees that go dormant, while some trees do not. Only deciduous trees, or trees that lose their leaves, go dormant. The trees that don’t need to go dormant during the winter have a special wax coating to protect their tree needles or produce sap to prevent their leaves from freezing.

Chlorophyll is what gives tree leaves their green color. As the seasons change and the air becomes cooler and the days become shorter, a tree can tell that it’s receiving less light. Trees convert that light to food in a process known as photosynthesis and use that food to give it the energy to grow. When the days become shorter, however, the tree lacks enough light to create the necessary energy, so the tree saves energy by breaking down the chlorophyll in the leaves. Green is the dominant color, but once the chlorophyll is gone, the beautiful fall colors of reds, oranges, and yellow are the colors that appear, though they have been there the entire time.

Preparing for Winter

Losing their leaves is the main sign trees are preparing to go dormant. They want to lose their leaves because they don’t want the water inside the leaves to freeze, which would damage the plant cells. As far as protecting the inside of the tree, which also contains a lot of water, trees go through incredible microscopic changes to keep them from bursting like a frozen pipe.

The first change a tree goes through is to make their membranes more pliable, which allows the water to come out of their cells. Then they keep the water in the spaces in between the cells.

The next way trees protect their cells from freezing is by sweetening their cells. Like animals, trees can store their food to prepare for winter. Part of the process of photosynthesis is the tree using light to make their own food by converting starch to sugars. Storing this sugar and sweetening the fluid in the cells protects the cells from freezing. This process is much like the antifreeze that keeps the radiator in your car from freezing over.

The final method is protecting the cells from crystallizing. This is done by dehydrating the cells using the two techniques above.

Stages of Dormancy

There are three stages a tree goes through when the weather starts getting colder: early rest, winter rest, and after rest. Each of these stages is marked by clear physiological changes.

  1. Early rest. This is the stage where trees are less active but can continue to resume growth with stimuli, such as warmer temperatures, water, or sunlight.
  2. Winter rest. This is the stage where trees have completely made preparations to protect themselves during the cold weather.
  3. After rest. This is the stage where trees push the water that was removed from their cells back into their shoots. The tree will not bud or grow yet; it stays in this after rest stage until temperatures stay above freezing. If a tree does not have this after rest period, and temperatures quickly rose then dropped again, any new buds or growth would die from the next frost.

Can We Help Our Trees?

There are a few things we can do for our deciduous trees as the weather starts to cool down. For example, removing dead branches to strengthen and protect your tree, pruning your tree to help prepare for a fruitful growing season after dormancy, adding mulch to the base to protect the roots from cold, fertilizing to prepare the soil for spring, and wrapping the trunk to protect your tree from sunscald.

So much is going on within the cells of your tree to help to prepare it for dormancy. Many trees don’t need help, but younger trees or unhealthy trees may need a little extra care to help prepare as the seasons change.

If you have any questions about your tree’s needs or need help preparing your tree for winter and dormancy, our knowledgeable and caring team at Mr. Tree can help. We take pride in providing quality service. We’re open 24/7 for 360 days of the year and have over decades of experience in tree care in Washington and Oregon. Whatever your tree needs are, we can help find a solution. We look forward to hearing from you.