Published: November 05, 2009 06:50 pm      

Fall color in an evergreen?

EDMOND — Homeowners may be beginning to wonder why their evergreens resemble a palette of fall color. Many pines and arborvitaes are exhibiting shades of brown and yellow in their needles. With all of the other pine problems running rampant, this may be alarming, but there is no need to start tree shopping just yet.

A change in color is common at this time of year for coniferous plants like the pines, spruce and arborvitae. Though plants in this group are referred to as evergreens, not all of the needles will stay forever. It is common for the older needles to discolor and drop at this time of year.

This process is referred to as natural needle drop. The older needles toward the interior of the plant will turn yellow or brown, and eventually drop. The needles on the tips of the branches will remain unaffected. Needle drop is not always a noticeable event to the homeowner; in some years it may even go undetected. The level of stress that a plant is put under will directly affect how extreme the loss of needles will be.

Most evergreens will go through this process, but the degree of needle drop can vary between different species. For instance, the Austrian Pine typically will retain three years of green needles. If the plant is under heavy stress,however, all of the needles could turn yellow except the current year’s growth. If the yellow needles outnumber the green this makes for a sickly-looking pine.

Scotch pines, like the Austrian, maintain needles for three years. Spruce trees also experience needle drop with age, but it might take a closer inspection to notice, because spruce hold their needles for several years. Arborvitae needles normally turn brown instead of yellow, and the needles remain attached longer than pines.

Yew plants experience needle yellowing and drop, but at a different time of the year. It is common for a yew to lose its third and second year needles in the late spring or early summer.

Though needle drop is a natural process, it is important not to confuse it with a serious disease or insect problem. The fact that this is a seasonal occurrence and should only appear on the interior of the plant will help to correctly diagnose the symptoms.

Even though needle drop can’t be prevented, it can be minimized by keeping the tree healthy and stress-free. Evergreens keep their needles during the winter, which means they are still using water for photosynthesis. So it is a good practice to occasionally irrigate through the winter to help prevent desiccation and freeze injury.

For more advice on this topic, or any of your gardening questions, please feel free to call the OSU Master Gardeners at

713-1125.

SAMANTHA SNYDER is a horticulture educator for the Oklahoma County OSU Cooperative Extension Service.