When I think of a tree, I think of how beautiful it is – the reflection cast upon the snow in the stark winter afternoon; the contorted branches, now barren of leaves, have icicles dangling at the tips. Snow lies in the crotches of the branches. How can this tree survive such bitter weather and continue to thrive again come spring?
Here is some insight into the “magic” winter transformation within a tree.
Deciduous trees, such as oaks, ashes and maples, drop their colorful leaves for a vital reason. The trees go into a type of dormancy and don’t make sugars for growth during the winter season.
Leaves, if left on, act like wicks and draw water from the tree, dehydrating it and potentially killing it. Also, if the leaves remained on, they would hold heavy snow and ice, which can lead to limbs breaking under the weight.
How do evergreen trees, such as spruce and pines, survive with their needles on during the winter season?
Well, they, too, shed their needles, but only every couple of years and then just the oldest needles.
They tolerate the weight of the snow because of their cone shape, which sheds snow easily.
Their needles have a waxy coating, so there is less surface area for water loss. And since they retain the needles, they carry-on photosynthesis when the weather is favorable.
Because of this activity, the tree will need water.
Where does it get water when the temperatures are freezing? Water can be found in the soil and inside the tree, but this is limited. When an evergreen loses too much water, you will notice the needles turn brown in the spring.
So how do both evergreen trees and deciduous trees survive these sometimes frigid temperatures with water inside them?
Well, trees have bark, which provides a physical barrier, but not much insulation, from the cold.
In the fall, a tree converts some of its food to sugars, which act like an antifreeze and lowers the freezing point inside the cells.
But all trees have a killing temperature. That is why you don’t see palm trees in Pennsylvania – they can’t survive to reproduce.
Wambaugh is a district forester with the state Department of Conservation and Natural Resources and is based at Elk State Forest in Emporium. She may be reached at 814-486-3353.