As seasons go through their changes, trees react to this annual cycle. Following a tree through our four seasons is much more interesting and dramatic than we give these majestic beings credit for.
Starting in spring, trees begin reacting to increasingly longer periods of daylight and warming temperatures. Cued by specialized detection cells, buds begin to open and new leaves begin to expand. Chlorophyll production begins which gives way to photosynthesis in these new leaves. Photosynthesis produces sugars which precipitate a period of rapid growth. New twig growth extends towards the sun, while new wood is created to support the above-ground mass of the tree. Roots are also extremely active in spring, as they grow to find water and absorb nutrients to support all of the metabolic processes occurring within the plant.
Summer Slow Down
As spring moves to summer, and daytime temperature highs increase, growth slows. The enzymes that power photosynthesis cease to function during the heat of the day. In many years, summer is also accompanied by decreased precipitation and low soil moisture, contributing to slow a tree’s physiological processes. That being said, most all buds containing next year’s leaves are set by mid-summer.
As summer sways to autumn, day length begins to shorten and trees respond by creating less chlorophyll. Of all the colors on the light spectrum, green is least useful to plants for photosynthesis. Green light is reflected from leaves, giving them their hue during spring and summer. In deciduous trees, as chlorophyll breaks down in response to longer nights, more green is allowed to absorb into the leaf. Anthocyanins and carotenoids are leaf compounds which are left behind and reflect reds and yellows respectively. Warm fall days followed by cool nights combined with adequate soil moisture is the combination for stellar fall leaf displays.
Trees begin their preparation for dormancy in fall so they can survive through winter. In deciduous trees, a layer of ‘scar tissue’ is formed between the leaf and branch attachment known as the abscission zone. Leaves are then dropped by a combination of gravity and wind. Hormones are produced that help prevent cells from winter dehydration. Likewise, cells are infused with compounds (lipids) that help prevent cells from freezing. The process of freezing water outside of these cells actually gives off some heat that can be absorbed by living cells of the tree.
Trees are remarkable organisms. Their ability to withstand extremes in our dynamic environment is quite a credit. As you are staring out your front window, admiring the your favorite tree, think for a moment just how much is happening at that occasion just under the bark of the seemingly peaceful being.
If you have questions or concerns about changes happening in your trees, please call Limbwalker at (502)634-0400 to schedule an appointment with one of our Certified Arborists®.