We are seeing very noticeable natural needle drop on some evergreens such as arborvitae, pines and especially spruce. This is a process where 2- to 4-year-old interior needles turn yellow, then brown, and eventually drop off. Those who aren’t familiar with this process often are concerned about the health of the tree. This is a natural phenomenon that occurs every year and does not hurt the tree. However, some years it is much more noticeable than others especially if trees have been under stress. In most summers, the stress is due to heat and drought but this year was likely due to too much rain restricting oxygen to the roots.
Be sure to check that only the older needles are affected –the needles on the tips of the branches should look fine–and that there is no spotting or banding on the needles that are turning yellow.
Since we have had a very dry year it is a good idea to water these trees as well. Drought will make natural needle drop more pronounced due to stress.