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Have you ever seen a stand of bare trees? They look dead and naked, how could they possibly still be alive? Oh but they are. We think of trees as lesser lifeforms, oftentimes. After all, they do not have the fancy coping mechanisms for cold that other (more mobile) life forms possess. Human beings use coats and furnaces. Animals store food and pack on the calories in preparation for winter. Many animals even enter a deep sleep, called hibernation, during which their body shuts down pretty much everything except respiration. In truth, all life forms come equipped to survive the frigid winter months and greet spring with a fresh new face. Trees are no exception. They go into dormancy. In this dormant state, trees cut off every unnecessary expenditure of energy. Even photosynthesis takes a back seat, and it is all thanks to a little thing known as ABA.
What is ABA, you ask? ABA is an acronym for abscisic acid. It is a hormone that triggers the tree to make some amazing changes. One of the most noticeable is the falling leaves. About the time that Old Man Winter comes knocking, ABA kicks in and tells the tree it is time for bed. One of the first places it gets to work is at the terminal bud. Terminal buds are the junction point between leaf and branch. In deciduous trees (such as oak, sycamore, poplar etc) the leaf separates at the terminal bud and lets go. Conversely, the evergreen (coniferous) family of trees stays green year round and needn’t be seen bare to maintain life.
The benefit of dropping leaves is great. Trees do not use leaves to stay warm…they use leaves to create food. During the harsh winter months, when the sun is distant and scarce in the sky, trees stop producing food. Their growth slows and their metabolism grinds to a crawl. They have no need for leaves, and they would only waste precious energy trying to hang onto them. It is here that ABA gets to work on BOTH deciduous and coniferous species of tree. One of its primary functions is to prevent cell division, thus suspending the growth of the tree. As with hibernation (in animals), impediment of growth conserves a great deal of energy for the tree. This, combined with losing the responsibility of nourishing leaves, results in an organism that has lots of stores saved to jump start it in the spring.
In the cases of trees kept indoors, the dormancy is staved off. If you provide your tree with stable temperatures and a consistent light cycle, it will not enter dormancy. The tree will keep all of it’s leaves, and it will be none the wiser in regards to the frosty situation just outside the door. This is not optimum for the overall health of your tree, however. The lifespan of a tree is dramatically decreased if it not allowed to enter dormant phases, cyclically. As is usually the case, nature knows best.
About the Author
Czok is a certified arborist. He has many years of experience in this field. He is a passionate conservationist and an impassioned tree surgeon. He enjoys his work because he loves trees.