YOUR PLANT MAY HAVE SUFFERED
WINTER DESSICATION (DRYING OUT) OR WINTER BROWNING INJURY.
WHAT IT IS:
ACCORDING TO AGRICULTURE AND AGRI-FOOD CANADA:
THE DAMAGE IS CAUSED BY EVAPORATION OF MOISTURE FROM THE NEEDLES DURING WARM OR WINDY PERIODS IN THE WINTER. This moisture loss cannot be replaced, since the soil is frozen and the roots are inactive.
Evergreens showing signs of discoloration in the spring indicate that winter browning or desiccation (drying out) has likely occurred. Needles can appear slightly or distinctly yellow, brown or red-brown, depending on the severity of the damage.
South and west-facing branches are prime targets for injury.
Newly established evergreens on exposed sites are also subject to winter desiccation (drying out) and browning. It can occur on pine, juniper, yew, cypress, spruce and ornamental cedars.
While unsightly, winter damage IS NOT ALWAYS FATAL.
Severe needle loss may occur, but if the buds are not damaged, new needle growth will occur in the spring.
ACCORDING TO THE ALBERTA MINISTRY OF AGRICULTURE, FOOD AND RURAL DEVELOPMENT
Springtime needle discoloration on previously healthy evergreens is often a symptom of some form of winter injury. Winter damage CAN ADVERSELY affect the appearance and growth of highly prized evergreens. Careful pruning will be required to restore their shape and form.
DRY SOILS are more likely to predispose roots to damage than soils that contain an adequate moisture supply.
A warm fall followed by abnormally low temperatures in early winter may result in improperly hardened plants, which are susceptible to freezing injury.
Late season nitrogen application will delay fall maturity and will increase susceptibility to winter injury.
Winter drying of needles can also occur in abnormally warm winters because moisture is continuously lost and cannot be replaced, as the plants are dormant. On warm, sunny winter days, radiation from sun or reflection from snow and light coloured buildings can increase leaf temperatures to 20 degrees Celsius over air temperatures. The moisture in the stems and branches becomes exhausted because of the increased loss triggered by warmer temperatures. Plants that are burlapped and experience a warming trend during the fall, winter or early spring can also experience heightened temperatures and excessive moisture loss.
WHAT SHOULD HAVE BEEN DONE TO PREVENT WINTER BROWNING:
FROM BOTH GOVERNMENT SOURCES INDICATED ABOVE:
- Reducing moisture stress during the growing season will reduce the risk of winter injury.
Water trees well during the dry summer periods.
- Water evergreens in the fall, after deciduous trees have lost their leaves, to ensure that the plants have sufficient moisture in the root zone to prevent freeze-drying. Water again before freeze-up, and after the second hard frost.
- Repeat this watering early in the spring, once the ground thaws.
- THE IMPORTANCE OF ADEQUATE FALL WATERING CANNOT BE OVEREMPHASIZED, SINCE WATER APPLIED IN THE FALL IS MUCH MORE BENEFICIAL THAN ANY BENEFIT OF WATER APPLIED IN THE WINTER.
This watering schedule will give the trees a chance to harden off before winter.
Erect canvas, burlap or slatted screens, or wrap burlap around the plant to lessen the sun and reduce the moisture loss due to wind. Timing of this erection and take down is critical, for plants that are wrapped during sudden warmer fluctuations in temperature during the late fall or early spring may 'sweat' within their burlap protection, and suffer dessication injury as a result.
Please note: Winter browning should not be confused with the normal shedding of needles during autumn. Depending on the species, needles turn brown and are shed after two or three years. This will occur naturally toward the centre of the tree, while new growth and previous year's growth remain normal at the outside edges of the plant.
