By Judy Kunz, Colorado Master Gardener

Why are my evergreens turning brown?

During the autumn months it is not unusual for the Diagnostics Lab at the Arapahoe County Extension office to receive samples of evergreen boughs that have browning needles. However, where the brown needles are located on the tree can be a key to a number of different factors.

Photo: CSU Extension Denver

If the affected needles are closer to the interior of the branch, this is typical of evergreen needle drop during the fall months and not a cause for concern. Just as deciduous trees lose their leaves in the fall, evergreens shed their older, inner needles also. Depending on the type of tree, normal needle drop can occur every two to three years for white pines. Ponderosa and Austrian pine shed needles every three to four years, extending up to every 17 years for bristlecone pines. If the tree is generally healthy with pliable branch tips, and has new growth from the previous growing season at the tips of the branches, the best bet is that it is simply normal fall needle drop.

However, If the brown needles are closer to the tips of the outer branches, it could mean a potential problem in need of attention. Common ailments include drought, de-icing salts used on nearby streets and sidewalks leaching into the root system, soil compaction from heavy foot traffic, or disease. For information on common conifer diseases see: https://extension.colostate.edu/docs/misc/NeedleCasts.pdf.

Illustration: Tree Canopy © UC Master Gardener Program of Alameda County

Tips For Evergreens Going Into Winter

Because almost all conifers are not native to the Front Range area, they can struggle throughout dry periods in winter because of lack of moisture and/or desiccating winds. They will continue to lose moisture through their needles if their water take-up through the root system is insufficient. Therefore, it’s important to give them an occasional soaking during dry periods when the ground is not frozen. A frogeye sprinkler positioned around the drip line of the tree (below the outermost branches) will deliver water where it is needed the most and help trees stay healthy going into winter.

In addition, heavy snow load can break branches. To avoid this problem, knock off heavy snows with a broom or shovel using an upward motion applied from underneath the branch.