Our Giant Thujas are starting to turn red. What is wrong and how do we rectify it?
Douglas County Colorado trees and shrubs
Hi, thanks for submitting photos. It appears that the forefront tree is the most stressed one of the three, and the one furthest away is still fairly green and healthy. Can you think of any environmental factors that might be inconsistent from one to the other? It appears that there is weed barrier cloth around the trees, and it's possible that it is interfering with water penetration to the root systems around the trees. How are you watering and how often do you water? How old are the trees? Were the trees planted properly? We had two very dry winters, 2017 and 2018, and if you did not winter water during these years, it could have stressed these trees. There are three applicable CSU extension publications for you to read, and the links are provided here:
You might also contact an arborist. We can suggest ISA Rocky Mountain Chapter for Arborists
and Associated Landscape Contractors of Colorado ALCC
I hope that this information is helpful to you.