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Williams: Evergreens also shed in autumn

Posted: November 15, 2017 - 2:32am

Fall is most closely associated with leaves dropping from deciduous trees, like oaks and maples. But did you know that evergreen trees, such as pines, shed their needles also?

"Evergreen" doesn't mean that the trees stay green for the entire life of the tree. It actually means that the leaves or needles stay green and attached to the plant for more than one year. Most evergreen leaves grow two to three years before shedding.

Pines and arborvitaes drop their needles in the fall after two years. Some species of juniper can keep their needles for 10 years or more. Broadleaf evergreens, such as hollies and magnolias, shed their older leaves in spring as new growth begins.

Pines shed their needles for several reasons: The older needles become worn out and lose their ability to produce nutrients efficiently; they may also become shaded out by the younger, more vigorous needles produced in spring.

Because there's a natural growth and shed cycle, shedding needles are replaced with newer needles every year. The old needles fall to the ground and become pine straw. This can be both a good and bad thing; the straw helps retain soil moisture around the tree but usually requires you to rake it into the landscape beds.

Now is when you'll most likely see some brown needles on your pine trees. If you examine your trees closely, you'll notice most of the discolored needles are located on the inner sections of pine branches. Needles on the outer portion of branches remain green. This is completely normal and doesn't mean that the tree is in danger of dying.

Environmental stress, such as drought or overwatering, will intensify needle drop in the fall. If your pine tree is showing discolored needles on an entire branch or is brown throughout the entire tree, insect or disease damage could be the culprit.

Other factors may contribute to evergreen needle drop throughout the year. Nitrogen deficiency will show up in a pine with similar symptoms as natural needle drop. Plants can move nitrogen from older to younger leaves to protect the new growth. This will cause the older needles to discolor and drop.

Waterlogged or extremely dry soils, insect injury, disease, air pollution, and chemical injury can also cause needle drop symptoms, but rest assured that fall needle drop is a natural occurrence and doesn't affect the health of the tree.

Enjoy witnessing the plant life cycle at work as the seasons change, and enjoy the free pine straw!

 

Tripp Williams is the Columbia County coordinator for the University of Georgia Cooperative Extension.

Email him at trippj@uga.edu.

 

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