Fall color is at its peak across much of Ohio. Not only are our deciduous trees beginning to drop their leaves but evergreens are too. Seasonal leaf drop is a normal part of the growth cycle of most trees, including evergreens.
Despite being called evergreens, conifer species like pine, spruce, and arborvitae shed needles in the fall. Often, this needle drop goes unnoticed. During times of drought when trees are stressed, needle yellowing/browning followed by needle drop can be more noticeable. How dramatic the needle drop appears also depends on the amount of growth that occurred in previous years. Robust growth results in a lot of needles to turn yellow when it comes time for them to be dropped. Conversely, limited growth years means fewer needles to turn and drop. It can be quite alarming to a tree owner when large numbers of needles turn yellow all at the same time. And this year, the color change and the number of needles turning color has been very pronounced.
Needle retention varies with conifer species. White pines retain their needles for two and sometimes three years, Austrian pines for three years, and spruces for five or more years. The oldest needles located along the interior of the branches begin to turn color and drop, leaving only more recent growth on the trees.
Interestingly, conifers such as baldcypress (Taxodium distichum), dawn redwood (Metasequoia glyptostroboides) and larch (Larix laricina) are deciduous and lose all their needles each fall. Unfortunately for these deciduous conifers, it has led to the demise of some when a new owner of the tree did not know that the loss of leaves was a normal annual event.
Notice the uniform pattern of yellowing on white pine and browning on arborvitae. Needle yellowing/browning occurs on each tree from top to bottom and only on the interior needles. If needles turn color in a random pattern or on the tips of branches, the culprit is likely not fall needle drop. Insects, diseases, nutrient imbalances, and other factors may be to blame.
A strong wind can quickly remove most of these yellow to brown colored needles from the trees leaving the most current crops of needles behind. This sudden removal of needles casts a “needle-shadow” on the ground on the leeward side of the tree.
So, do not be alarmed at the natural shedding of these needles this year.