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Over the Garden Fence

Where gardeners come to find out what's happening out in the yard.

Yellowing Needles on Our Evergreens

Posted by Richard Hentschel -

Down the Garden Path

Richard Hentschel, Extension Educator

It happens every year as fall begins to arrive, yellowing needles on our evergreens. This year you can see a lot more of this as our evergreens prepare for winter, adjusting for our hot, dry summer. All our needle evergreens maintain several years' worth of needles in any year. Pines for example will typically keep three years of needles where spruce likely keep four years of needles. When there are several growing seasons that have been good, they can keep even more. In less favorable years, like this summer and if the evergreen tree is not been vigorous, you may only be able to see two 2 years' worth of needles or some cases, the only needles on the tree will be current years' and the annual rate of growth is less than ideal. Evergreens also include those plants that do not have the typical needle like yews, junipers and arborvitae.

As the interior (older) needles continue to get less sunlight because of newer growth shading them, they become less efficient in producing energy for the plant and as the evergreens prepares for the winter, they will begin to shed these needles. This is where that bed of evergreen needles come from that we see underneath those big evergreen trees.

Evergreen needles can also yellow due to needle casts and blights and scale insect feeding. Scale insects while young look similar to an aphid and later a small lump or bump on the stems. There are several needle diseases that attack older needles leaving just current year needles intact on the evergreen.

This needle lose is going to occur regardless of how well an evergreen plant is doing. We can do some things to promote healthy evergreens. This fall especially, be sure to water your plants two or three times before you take the hose off the spigot for the winter. Root systems are still growing in mid and late November, so mark your calendar to make that last watering around thanksgiving. You should plan on feeding your evergreens next spring to help in the recovery from this summer. Evergreens, like every other plant in the yard did not produce the nutrient levels that would provide for good root growth and new needle growth next year.

Other factors that impact any trees health is siting and soil conditions. Trees planted in less ideal locations or if the conditions have changed (was full sun 15 years ago and now 50% shade) will impact how well a tree performs. If the soil conditions are not the best for drainage or if in a sandy soil that drains too quickly, then the trees will also be affected. The typical evergreen tree likes full sun. Some of our small evergreens will grow in shadier locations to a point like yews and arborvitae. Junipers are a full sun evergreen.

If we do not get enough rainfall this fall into early winter, plan to water. It is the least expensive thing you can do to promote recovery and good health.

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