This time of year, some people become concerned about the health of their evergreen trees. Needles are turning yellow and dropping and they begin looking for something to fix a problem that doesn’t exist.
While conifers are green year round (thus evergreens!) they don’t hold all of their needles forever. Like deciduous trees, they too 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.
Signs of needle drop are a distinct yellowing or browning of the needles towards the interior of the tree. The ends of the branches stay nice and green. This needle drop is a normal occurrence and you shouldn’t be worried about this condition. If the tips are brown, that’s another story. Brown tips are not annual needle drop.
Some years, the needle drop can be slow and barely noticeable while in other years it’s quite obvious. 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. 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 just to be on the safe side. 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 this stress might be;
- Over watering. A soil that drains poorly and stays wet is a sure contributor to unhealthy roots.
- Drought conditions or under watering 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 dying material and won’t spread to your tree. 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 of new, green needles could be a sign of fungus. For a positive ID, take a sample to your local extension office.
A positive ID is necessary to determine if and when treatment is needed.