This time of year I get plenty of questions from people that become concerned about the health of their evergreen trees. They are seeing needles that are turning yellow and dropping. The good news is that what is happening isn’t a problem at all, but a natural occurrence.
While conifers are green year round (thus evergreens!) they don’t hold all of their needles forever. Like deciduous trees, they experience an annual needle drop, they just don’t drop all their needles at one time. In the majority of evergreen species this needle drop occurs in the fall. Some years, the needle drop can be slow and barely noticeable while in other years it’s quite dramatic.
Signs of needle drop are a distinct yellowing or browning of the needles towards the interior of the tree. The ends of the branches remain green and flexible. If the ends of the branches are brown, or the tips of the needles are browning, that’s another story. Browning that occurs in the season’s current growth is not annual needle drop.
Evergreens also shed their needles differently from one species to the next. Evergreens like white pine and arborvitae shed one year old needles. Austrian and Scotch pine keep their needles for three years and spruce and fir trees keep theirs for several years, too. Keep in mind that every year there are needles that are the required age to drop so you’ll notice this happening each year. White pine has some of the most dramatic needle drop. Some years the yellow needles will outnumber the green ones making the tree look pretty unhealthy.
If you notice your tree with an abundance of yellow needles you might consider your cultural practices. While even a healthy tree has annual needle drop, a tree that is stressed will show more yellowing, earlier in the season. Some factors that contribute to stress in trees might be;
• Over watering. A soil that drains poorly and stays wet is a sure contributor to unhealthy roots.
• Drought conditions can cause early and severe needle drop.
• Lack of nutrition is a consideration but if the tree is in a lawn area that is fertilized regularly, the trees should be getting adequate nutrition.
On old needles that have fallen you might notice black spots or other discoloration and think the tree has a fungus. On old, dying needles the spots are most likely a non disease causing fungus that has moved in to begin the decomposition process. This fungus only feeds on dying material and won’t affect healthy needles. However, if you are seeing spots or discoloration on the current season’s needles that could be an indication of a problem. Look for signs of insects or mites. Spotting or banding (a stripe around the needle) on green needles may be a sign of fungus. For a positive ID, take a sample to your local extension office.
A positive ID is always necessary, for any problem, to determine if and when treatment is needed.