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The Beauty of Winter Trees: Tree Following, February 2016

February 10, 2016

winter red mapleI did not post about my red maple (Acer rubrum) tree in December or January. The busyness of the holiday season explains December, but in January I just couldn’t figure out what I wanted to say about the tree.

Like all deciduous trees in cold climates, my red maple goes into winter dormancy after it drops its leaves in the autumn. It’s tempting to think there is nothing going on with the tree during the winter months, but that is not true. The dormant tree is still an important presence in my life, and the first thing that strikes me about trees in winter is their stark beauty, especially when their limbs are limned in snow. The contrast of white snow on dark bark is striking and emphasizes the tree’s vertical shape.

We often talk about the visible winter form of a deciduous tree as its “skeleton,” but dormancy should not be confused with death.  We can think of the winter dormancy of plants as more like sleep than like death, a restorative process that protects health. Part of the beauty of deciduous trees in winter is that they have a hidden life pointing us toward spring.

An attempt to learn more about the winter dormancy of trees led me to a Virginia Tech website on tree science. Here I learned that dormancy is a survival strategy that helps protect trees from the harsh environmental conditions of winter, enabling them to live long lives (hundreds of years long in some species). I also learned that there are stages of dormancy and that these stages are triggered by length of night and day and by environmental conditions like temperature.

As the nights got longer in fall, my tree entered the stage of “pre-dormancy,” when growth slows dramatically. This is when the tree’s leaves stop producing chlorophyll and the brilliant colors of fall foliage appear. By the time the tree enters true dormancy, it has dropped its leaves and stopped the growth of new shoots. Dormant shoots have “resting buds” that are covered in protective scales. Once the tree is in true dormancy, it won’t emerge from that dormancy until it has experienced a “period of prolonged chilling” (500-2000 accumulated hours of chilling, depending on the tree species and how far north it grows). As the days get longer in late winter, the tree enters the “post-dormancy” stage, when the resting bud is capable of growing but will not do so unless temperatures get warm enough. It is warm spring temperatures that will lead the tree to “break bud,” with flowers and new leaves.

Soon, I will be aware of subtle changes in the bare shoots of my maple tree that signal the transition to post-dormancy. In late February and early March, all the little shoots in the tree’s canopy will begin to swell with new life and the promise of spring.

winter maple canopy

Tree following is graciously hosted each month by Pat English at The Squirrel Basket. In her Cardiff, Wales location, trees have already broken dormancy and begun to bloom!

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23 Comments leave one →
  1. February 11, 2016 9:59 am

    as yours hibernate, ours aestivate. But our leafless stage is brief. Almost as if the fresh leaves push off the old ones. Missed my window to prune the fiddlewood while it was between leaves.

    • February 13, 2016 9:27 pm

      Diana, I had to look up the meaning of aestivate; thanks for improving my wood power! 🙂
      The leafless stage here is definitely not brief; it is more than half the year. My tree lost its leaves in October and won’t grow new ones until May.

  2. February 11, 2016 12:11 pm

    Interesting – and an elegant tree in the snow.
    I am thinking our trees here don’t go truly dormant, as in recent winters we have hardly any icy weather at all. It’s scary to think a tree won’t wake up again unless it’s chilled for long enough first.
    All the best 🙂

    • February 13, 2016 9:33 pm

      Pat, I think the need for a certain number of hours of chilling before a tree can come out of dormancy is an evolved protection against being tricked by unseasonably warm weather in winter. Here, for example, we usually have a warm spell in late January (called “the January thaw”) which is then followed by the coldest weather of the year. Trees that broke dormancy during that warm spell would probably be killed by the subsequent cold and therefore not reproduce, ensuring the survival of those that had a chilling threshold appropriate to their climate. (As I’m writing this in the late evening, the thermometer on my deck reads -15F, -26C.)

  3. February 11, 2016 11:11 pm

    We have remarkably few dormant trees but perhaps that’s to be expected in our mild climate, where winter poses few hazards. We struggle to grow certain fruit trees (cherries, plums) precisely because they don’t get the chilling they need to enter dormancy and prepare for flowering. However, the few trees that do go dormant, even if briefly, always add some excitement to the garden when they emerge, as our ornamental pear tree (Pyrus calleryana) did this week, springing into bloom as if by magic!

    • February 13, 2016 9:36 pm

      Kris, The blooming of those fruit trees in early spring can be a magical moment. During the many years that I divided my time between Maine and Gettysburg, PA (on the Mason-Dixon line), I would often fly home to Maine for our “spring break” in March. I would leave Maine in the snow to go back and finish the semester; and often when I landed in the Baltimore-Washington area a few hours later, it would be to the sight of flowering pear trees.

  4. February 12, 2016 12:28 am

    Writing is hard work, we all have times when it is hard to find what we want to say…I’m glad you referenced the Virginia Tech site which I use as well as, if you are not using the University of British Columbia, and the University of Missouri sites you might find them useful as well..

    • February 13, 2016 9:37 pm

      Charlie, This was the first time I had stumbled upon the Virginia Tech site, which I will go to again. Thanks for the tip to check out the UBC and University of Missouri sites.

  5. February 12, 2016 4:31 pm

    Hello Jean, I can’t figure out what combination of day-length, average temperatures, hours chilling and number of frosts trigger early spring plants to start flowering. Everything is almost a month early here. Daffodils are out in full force, the Camellias are open and even the Magnolias are beginning to emerge. It’s all very risky as we can still have hard frosts into early April.

    • February 13, 2016 9:44 pm

      Sunil, From what I read, I got the impression that these were very specific to local conditions. I am imagining that this is an evolutionary process in which plants that emerge from dormancy too soon (or too late?) don’t survive to reproduce. We are about to have our coldest night of the winter tonight, so I’m happy that my plants are in dormancy and that perennials are protected by several inches of insulating snow (although not the feet of insulation we had at this time last year).

  6. February 13, 2016 4:07 pm

    I love dormant trees, they have such presence, even without the added beauty of snow. And I also love knowing that they are not, in fact, dead, but will soon spring in to life. I look forward to seeing the leaves unfurl on your maple in due course.

    • February 13, 2016 9:52 pm

      Janet, I love the stately presence of the dormant trees, too. Since I began following this tree when it was in bloom and about to get new leaves last May, I will probably be on to a new tree before this one gets leaves again. Although our latitude is south of yours, the cold temperatures mean that spring comes very late here.

  7. February 14, 2016 12:20 pm

    The schedule for dormancy in Savannah is quite interesting. The live oaks have not yet lost their summer leaves. It is so peculiar.

    • February 15, 2016 9:55 pm

      Jayne, I wish I understood this whole process better. I wonder if trees as far south as Savannah don’t go into true dormancy but only a period of quietude of pre-dormancy that they can emerge from as soon as temperatures get warm enough to support new growth.

  8. debsgarden permalink
    February 14, 2016 5:34 pm

    Interesting post! I love trees throughout the year, in all stages. Your acer with its snowy accent has a lovely form. I am not sure how many hours of dormancy our deciduous trees require. I doubt we get much more than 500 hours of chill hours, if that.

    • February 15, 2016 10:00 pm

      Deb, I found an interesting fact sheet from the Alabama Cooperative Extension Service (here) on chilling requirements for fruit trees in Alabama. They note that the chilling requirement is for hours at or below 45F, not at or below freezing.

  9. February 14, 2016 6:59 pm

    Fascinating tree science. I love the dormancy of trees.

    • February 15, 2016 10:01 pm

      Donna, It’s a fascinating (if somewhat confusing) subject.

  10. joenesgarden permalink
    February 14, 2016 8:10 pm

    I thoroughly enjoy how you delve into a topic so you, and your readers, will better understand. An educator to the core. Thank you.

    • February 15, 2016 10:02 pm

      Joene, It’s true. 40+ years of teaching habits can’t be undone by a year or two of retirement. 🙂

  11. February 17, 2016 4:03 pm

    Dormancy is more like sleep than death – very well put. The trees take their annual sleep through the months of winter unlike the nightly slumber of people.

  12. February 28, 2016 10:28 am

    *I hate WordPress. It wants me to log in. I don’t want to log in (I am admin for someone else’s website). So I changed my email and it ate my comment. Which was to say: I don’t love winter, so I have challenged myself to embrace it with my camera. I love trees at all times of year, but hardwoods in winter charm me especially. Leafless, they appear vulnerable, their limbs lifted in supplication to the sun to please come back to us!

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  1. Tree following link box for February 2016 | The Squirrelbasket

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