Evergreen Winter Injury
It is that time of year again, and the Schutter Diagnostic Lab has been receiving several samples of evergreen trees and shrubs with symptoms of winter injury/winter burn, including evidence of browning needles and branches. These symptoms can appear without warning in the spring, and can seem very alarming, though many trees will often grow out of it, especially if taken care of by watering and watching for new growth.
 Winter Injury symptoms can be seen on the needles and branches (Photo: Eva Grimme) |
This is a cultural/environmental issue:
Resulting from minimal winter snow cover, extended periods of low humidity, and spring temperature fluctuations; narrow and broad-leaved evergreens (especially spruce, Douglas-fir and pines) are subject to drying out, especially if supplemental irrigation is not applied to the plants during the fall months. This results from the plants continuing to lose moisture through transpiration at a rate faster than it can be replenished. Common symptoms include red, yellow or brown discoloration of foliage, especially on needle tips, and can sometimes affect entire branches. Damage is more pronounced on the south and south-west sides, and can also be more severe in areas with high wind exposure, during periods of large fluctuation between daytime and nighttime temperatures, and on younger/newly transplanted trees and shrubs without well-established root systems.
These symptoms might seem alarming, but will become less obvious as soon as the tree pushes the new growth and/or drops its dead needles. As long as the buds are soft and green, there is still good growth and life in the tree. It is important to make sure your trees are watered thoroughly and regularly during dry periods, especially into the fall.
For information about caring for stressed trees:
https://ag.umass.edu/fact-sheets/helping-trees-to-manage-stress
https://www.bartlett.com/resources/simple-steps-to-aid-stressed-trees.pdf
For information about fall and winter watering:
https://extension.colostate.edu/docs/pubs/garden/07211.pdf
Abiya (Abi) Saeed
[email protected]