We get a lot of calls at the nursery this time of year from people concerned about their evergreens that have suddenly developed brown or yellow needles on the interior of the tree that are now beginning to drop. It is particularly noticeable on long needled Austrian pine and on columnar arborvitae. Let me set your mind at ease. This is a natural occurrence that happens every fall, although some years it will be more pronounced than others.
Although called “evergreens” these plants don’t hold their leaves (or needles) forever. They drop in the fall just like maples. But unlike maples that drop all of their leaves every year, evergreens hold their needles for 2 to 5 years before they drop. So, if it only happens in the fall, and only affects needles further down the branch (not this year’s growth) then you can rest assured that your tree is just doing what nature intended.