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arborvitae and winter kill #650580

Asked June 13, 2020, 9:00 PM EDT

I have 9 arborvitaes that I planted from 1 gallon pots that I hoped would serve as a screen.  They are over 5 feet tall now. They have done great up till this past winter.  They have some green, but are pretty brown otherwise.  I am wondering if I should pull them out, or if there is hope for them.  I hate to shear them, but maybe that is the only solution if I want to keep them.  I tried to water them during the very dry and warm periods, but I'm wondering if that just encouraged them to think spring was near and made the very cold temperatures that often followed worse for them.

Jefferson County Colorado

Expert Response

There might be some hope for them yet! But, you might have to do some pruning (see the final link I've included below).

This may be a case of winter burn from the spring weather like you mentioned. We are seeing a lot of Winter burn/desiccation on trees and shrubs across the front range this year due to the combined sudden freeze in October 2019 and our late spring freeze this year. This is my best guess for what may be happening. This page has a great overview of this issue, I highly recommend a read through it: https://hort.extension.wisc.edu/articles/winter-burn/

If Winter burn is the cause, no treatment is required other than regular water during the growing season, and monthly water during the fall and winter when there has been no precipitation for 3-4 weeks and temperatures are over 40F.

General recommendations:
  • Prune out dead branch tips in mid-summer after new growth has emerged later this year. Always prune just outside/exterior to green needles.
  • To help protect trees against future sudden temperature drops in fall, and over the winter, hand water monthly when there has not been precipitation and temps are above 40F. In anticipation of a temperature drop, a good soa
  • king to get moisture down 12+ inches will help the tree protect itself.

Additional References:

An Ask Extension Expert Replied June 18, 2020, 2:17 PM EDT

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