White fir (downed by lightning)

Have you noticed that some of the white firs (Abies concolor) in the Colorado Springs area are suffering? Many of these beautiful native trees seem to be having trouble this year, and experts are stumped. The needles start to turn a slightly lighter shade and drop, sometimes in a spiral pattern from the top down. Looking at the whole tree, it looks like it is declining gradually overall. The problem is affecting white firs of all ages and in all planting situations, non-irrigated, irrigated, sandy soil, clay soil, etc.

Of course, all evergreens naturally lose needles every year from the interiors of their branches. As the trees grow, those needles become shaded and no longer useful in the photosynthesis process. So the efficient trees drop those needles and concentrate their energy on the newer needles on the branch ends. With this condition, which has been informally dubbed “white fir decline,” all the needles along the branches are dropping. Another interesting feature is that these trees seem to have their upper branches covered with more cones (fully and not-yet-fully developed) than usual. (more…)