Suddenly this fall, my evergreen trees have many needles that are starting to change color, or turn yellow. My tree isn't dying, is it?
Fall Needle Drop on Eastern White Pine University of Nebraska- Lincoln Extension |
Fall Needle Drop on Austrian Pine University of Nebraska- Lincoln Extension |
Did you realize that evergreen needles change color in the fall too, just like deciduous trees do? It's true and it often causes alarm in homeowners when their evergreen trees start to drop needles.
Although most conifer trees are considered to be "evergreen", their needles don't live forever. What makes them evergreen is that their leaves persist more than one year before falling. Since new needles are added every year, there is always an overlap between green needles and those that are due to fall.
Older needles on the inside of evergreen trees are shed each fall after they turn yellow, brown or reddish tan in color. Sometimes this natural process is very subtle and goes unnoticed because only the inner most needles area affected, as in the picture below. Pine trees can hold their needles for 2-5 or more years, depending on the species. Spruce trees generally hold onto their needles longer than pine trees do, approximately 5-7 years.
Here are some of the pines commonly grown in Nebraska and the number of years they hold their leaves:
|
Two Years
Eastern white pine Jack pine (2-4 yrs.) Scotch pine (2-4 yrs.) |
Four Years
Austrian pine Red pine Swiss Stone pine |
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Three Years
Korean pine Japanese Black pine (3-5 yrs.) Japanese Red pine Japanese White pine Lacebark pine Macedonian pine Ponderosa pine |
Five Years
Bosnian pine Mugo pine |
One evergreen tree that is very noticeable as it loses its leaves in fall is Eastern White Pine. This tree only holds its needles for two years which leaves less growth at the tip of branches to hide the needles as they are shed. Combined with the soft texture and open structure of the Eastern White Pine this makes fall needle shed easily seen.
Fall needle drop is a natural condition and is not a sign of disease or insect infestation, however, any factor that increases stress on evergreen trees will intensify the autumn needle drop. Stress factors include drought, herbicide injury, root damage and insect or disease damage.
Natural needle drop occurs only on the inner needles; if entire branches or needles at the tips of branches are dying, then something else is happening. A sample of the affected branches should be submitted to your local Cooperative Extension office for diagnosis. A close inspection of any brown foliage should also be done to eliminate the presence of fungal leaf spots, spider mites, aphids or other potential pest problems.
Believe it or not, there are actually a few types of conifers that shed all their needles EVERY year. These deciduous conifers include larch, bald cypress and dawn redwood. The larch with its golden yellow and the bald cypress and dawn redwood with their bronze hues can add great beauty to the fall landscape. Such trees are unusual enough that more than one story has been told about people that removed such trees after they were mistakenly determined to be dead. Yikes!