Hello fellow readers,
Ellie and Barbara on the Appalachian Trail
Over the weekend I enjoyed a hike along the Appalachian Trail with a longtime friend from Boonton NJ. While meandering the rocky terrain peppered with hemlock and spruce, Barbara asked why some trees are evergreen and others are not. Good question. Let’s ask the trees.
During the growing season leaves and needles photosynthesize to make food for the plant. Come fall, as daylight shortens, it signals plants to hunker down for winter. Deciduous trees cut off their leaves’ link to water and minerals and drop off after only one growing season.
White Pine is not shy about disrobing.
Evergreen foliage, despite their name, doesn’t live forever. During the fall, older needles die and fall off as well. Pine trees hold their needles from two to five years or more, depending on the species. Spruces generally hold onto their needles for five to seven years. Hence every autumn some evergreen needles are falling, though the process often goes unnoticed because only the innermost needles are affected. Except for Eastern White Pine (Pinus strobus) who are not shy about disrobing. They hold their needles for only two years and have an open structure and less growth at the tip of their branches to hide the needles as they undress.
Evergreen branches slowly bend down layering on top of each other for protection “like tiles on a roof.”
Back to Barbara’s question why some trees are evergreen. Forester Peter Wohlleben writes in The Hidden Life of Trees why certain species live in certain areas explaining a tree “can conquer enormous geographic range. And that’s basically what spruce have done…. Spruces store essentials oils in their needle and bark, which act like antifreeze. And that’s why they don’t need to jettison their green finery” in winter. “As soon as the weather warms up in the spring they can start photosynthesizing. Not a day is lost…” Hence why evergreens survive even in frigid regions of Siberia and Canada with very short growing seasons. Not only that, they have fascinating “defense mechanisms” to protect them from snow and winds. Spruce trunks are usually straight which keeps them in balance even with heavy loads of snow when branches “gradually angle down until they are layered one on top of another like tiles on a roof. Arranged like this, they mutually support each other,” Peter Wohlleben explains.
Folks worry more about evergreen trees toppling over in high winds with snow loads. Understandably so, given last winter’s one-two-three nor’easter punch. The thing is, spruces grow slowly for sure-footedness “and statistically speaking, the danger of being blown over doesn’t increase significantly until the trees are more than eighty feet tall,” per Peter Wohlleben.
So, the question isn’t why some trees remain evergreen. It’s how. And how is the miracle of nature’s resilience and ability to adapt, flourish, and provide respite for others. We have much to learn from trees. Garden Dilemmas? AskMaryStone@gmail.com
