Seasonal needle drop

Every fall, people look forward to the fall colors as deciduous tree leaves change colors and drop in preparation of winter. We expect the leaves of deciduous trees to change colors. What many people are unaware of, though, is that most conifers also drop their needles at this time.

Every fall, conifers shed some of their needles. This is a natural process known as Seasonal Needle Drop. The amount of needle-loss is dependent on species and environmental conditions. The occurrence of seasonal needle drop is often mistaken for disease or insect damage.

Seasonal needle drop typically consists of gradual yellowing and browning and eventually loss of older needles from the top to the bottom of trees.

This starts in late August and can continue through October. Some species are affected more than others. Needles that drop due to age may have some spots or blemishes. However, they do not display typical symptoms of disease or insect damage. Disease is often the cause of death for younger needles, branches, or the thinning of needles on the lower branches.

White Pines are some of the more seriously affected trees. Third and sometimes second year needles yellow and fall seasonally throughout the entire tree.

Austrian and Scotch Pines typically lose only fourth year needles. Symptoms are not nearly as dramatic as in White Pines.

Cedars often display browning of leaves and flagging of older branchlets. Eventually entire branchlets are shed.

Spruce and Fir generally maintain many years of growth. Seasonal needle drop is typically not very noticeable and is often only visible if looked for on inner branches.

Management for seasonal needle drop is not necessary. As long as the yellowing and needle drop is restricted to older growth and is not extreme, it is likely not a problem. Maintain tree health by following good cultural practice.

Natural needle drop occurs only on the inner needles; if entire branches or needles at the tips of branches are dying, then something else is occurring. A sample of the affected branches should be submitted to the local extension office for diagnosis. A close inspection of any brown foliage should also be done to eliminate the presence of fungal leaf spots, spider mites, aphids or other potential pest problems.

For questions, contact the Fallon/Carter County Extension Office at (406) 778-7110 or falloncarter1@montana.edu.