In September, we start receiving calls from our concerned customers about their Pine and Spruce trees “turning brown”. This needle browning occurs every fall and is normal as long as the tissue that is changing color is the older needle tissue and not the current year’s growth. “Fall Needle cast” in Spruce and Pine trees is analogous to the annual leaf drop of deciduous trees, but just on a much longer schedule. As needles age and become less productive/efficient, it is necessary for the tree to shed this material before it requires more energy to maintain than it produces. Spruce trees are often less noticeable with their needle cast because they tend to have denser canopies than Pine trees.  You would have to get closer to see the needle cast in the Spruce, but the changing of color in the Pines can be seen from a significant distance.  Many of the Pines have already begun their change in the foothills in Boulder, Golden, Evergreen and Conifer.  White Pines are always the easiest to notice as they drop their needles in the fall, and we always receive several concerned calls about the various White Pine species.

The timing of the “Fall Needle cast” is also important. Because weather and daylight are the dominant triggers, we expect the vast majority of the trees to show their needle browning at about the same time. Damaged or stressed trees can begin to show needle browning early. Early needle browning and subsequent needle drop is something that deserves a little investigation into what else might be happening. Stress can come from sources like recent transplanting, insect damage, drought, or soil compaction.  If you have questions or concerns about what is happening to your trees give us a call and we can help with the investigation.