Some needle loss is normal for evergreen trees.Thinkstock/Comstock/Getty Images
Evergreen trees go through a yearly process called seasonal needle loss. Most healthy conifers retain the color of their needles throughout the winter, but during the fall, the older needles near the trunk turn bright yellow and fall off. These are replaced by new tufts, which remain with the tree for several years before undergoing the same process. Seasonal needle loss is part of the regular cycle of an evergreen and very commonly mistaken for a health problem. However, thinning of the needles isn't always normal, and symptoms such as heavy foliage loss, discoloration and direct damage to the bark and branches may indicate a more serious problem. Taking the appropriate steps will give your evergreen a chance to recover.
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Avoid using lawn herbicides near your tree. An evergreen with wide-reaching roots can absorb these chemicals up to 100 feet from the application point. These substances and certain soil sterilants damage needles and buds and cause shedding. If you must use them, apply them at an appropriate distance in cooler weather when the winds are light and blowing away from your tree.
Keep your tree properly watered. Evergreens are susceptible to drought and sudden alterations in their watering schedules. They may have difficulty adjusting to a dwindling water supply. Ensure their soil is able to deliver moisture effectively. Check for soil compaction and obstructions such as concrete and foreign objects that could hinder absorption.
Protect your tree from animals. Several types of wild animals will debark your evergreen or eat the foliage. Dog urine will discolor and damage low-lying needles. If the tree is partially stripped of bark, it will stunt growth in sections and if it's completely girdled, your tree will die. Take all realistic precautions to avoid attracting animal activity in the vicinity of your evergreen.
Avoid fertilizing your tree and stick to giving it abundant sunshine and water, unless there are clear signs of malnutrition. Needles should be a healthy and dark green. If you suspect your evergreen isn't getting enough nutrients, spread a tablespoon of balanced fertilizer on top of the soil around your tree. Use water or wait for the rain to disperse the nutrients into the soil. Don't place the fertilizer under the soil or near the roots, as this may kill the tree.
Kill surrounding weeds and overgrowth manually, if possible. Weeds interfere with light absorption and divert the uptake of water and nutrients. Evergreens are susceptible to injury and damage from a variety of chemical substances and are better tended to without them.
Keep your tree outdoors as often as possible. Conifers used indoors as Christmas trees and decorative items can't survive long in those conditions. If you must have it inside, cover the pot with straw and, if possible, snow.
Watch for signs of excessive watering. If most of your tree is turning brown and the leaves are dying, shut off its water supply and try letting it find some water on its own, using its root system.
Take note of thriving species of evergreens in your area. These are the trees that will do well if you decide to plant more conifers.
Spraying synthetic coyote urine near an evergreen will help scare away deer, which can damage these trees — deer are frightened of coyotes. You can buy a bottle at most gardening and hardware stores.