by: Maureen Sexsmith-West
ISA Certified Arborist, PR4600A
Evergreens are susceptible to desiccation over the winter months. This type of injury is a form of dehydration.
This results when the moisture lost through the foliage exceeds the moisture taken up by the roots. If you have regularly watered throughout the previous year and gave your trees a good drink before freeze up this may not be an issue. Warm temperatures, low precipitation and Chinook winds, reflective heat off of light colored buildings, large pane windows, rocks, brick and cement walks are all contributing factors. Most susceptible to reflective damage are cedars, pines and junipers located close to buildings. Needles will begin to dry out. This can be deceiving since many will maintain their green color and remain attached until spring when they will turn yellow/brown and drop.
GET YOUR GARDEN HOSE OUT OF STORAGE. GIVE YOUR EVERGREENS A DRINK PERIODICALLY THROUGHOUT THE WINTER MONTHS WHEN CONDITIONS WARRANT. A slow drip will replenish lost moisture around the roots. This will greatly improve the health of your trees, fighting against insect and disease problems in the coming year, increase their life expectancy and reduce long term maintenance costs.
One of the best ways to prevent this type of damage to your trees is to maintain good soil moisture throughout the year. Mulching a 3- to 6-foot diameter area around the base of the tree with an organic material like coarse wood chips with help achieve this. Even a seasonal application that is removed and later recycled into your garden beds in the Spring is helpful.
Other Causes of Browning
Avoid applying salts for snow clearing. Salt will alter the pH level of the soil making it difficult for most varieties to extract nutrients.
Prolonged warm periods can trick the tree into thinking it is spring. Other damage can occur if a sudden temperature changes occur. This can damage the buds which had been set for next season. This can’t be checked until the next growing season. Some will begin to move the fluids from the roots into the trunk and begin bud swelling leaving them vulnerable to mid-winter temperature changes and frost damage. Natural needle shed occurs in the fall when the oldest needles turn yellow and fall off (interior part of the tree).
Rabbits, porcupines and mice love to eat the bark. They will also find shelter under the foliage from predatory animals. If they chew bark off all the way around the twig – this will cause girdling – no sap can flow past this point and the twig dies back.