Question
my 2nd winter transplants about 30" tall are drooping and turning brown, I live in northern nevada and the weather is dry and cold. I have been watering them once a month since winter hit. What might be the problem and what should I do ? Thank you, Toby

Answer
Hi Toby,

It sounds like the problem with your arborvitae is winter dessication injury or winter burn.  This occurs when cold dry air/winds dry out the leaves of evergreen plants.  It is more common on plants that are newly planted since the roots have not colonized the soil.  

Winter injury or winter burn occurs when the soil is frozen and winds draw moisture out of the leaves.  Since the ground and water in the soil is frozen, plant roots are unable to take up water from the soil to replace what has been lost from the leaves.  If the burn is extensive, the plant will generally drop the damaged needles.  This problem can occur on both conifers and broad leaved plants that retain their leaves during the winter.

Trees should be planted as early in the fall or late summer as possible and fertilized with a root stimulating fertilizer (generally has a higher amount of phosphorous).  Newly planted trees and shrubs should be watered frequently during the winter when the ground is frozen.  One the water freezes, the plant roots are not able to take it up.  I would suggest watering every week during extended periods where the ground water is frozen.  For your other plants, those that are watered biweekly throughout the growing season will be better able to handle stress.  Watering well during dry periods in fall is also helpful.

Antidessicant sprays can be applied in late fall and mid-winter if desired.  They may provide some protection and help prevent dessication.  Some products you may find are named Wilt-Pruf, VaporGuard, Stressguarad and Nu-Film.  These products provide a waxy coating that helps prevent the needles from drying out as quickly.

Good luck with your plants!
--Jen