Arbor Vitae Problem
My daughter has a row of Arbor Vitae next to her deck. See pics. The side near the deck is pretty green. The other side is dying back. The side that is dying back does have southern exposure. No obvious insect damage. Maybe being burned by sun?
Howard County Maryland
We viewed the photos you submitted and cannot say for sure what you are dealing with. The plants may be stressed due to drought, vole damage http://extension.umd.edu/hgic/voles, poor drainage, lack of sunlight, bagworms http://extension.umd.edu/hgic/bagworms-trees-and-shrubs, etc.
The brown area will not recover and you will have to prune it out. If extensive, you may have to replace the whole tree. If the plants are in the shade and planted close together with poor air circulation there will be root competition for moisture and nutrients. They will grow much slower and thin out in this environment.
Arborvitae grow best in full sun in a moist well drained area. This is how they are grown in nurseries. Make sure they are spaced for good air circulation, mulch is no thicker than several inches and keep away from the base of the trunk, and water during dry periods.
Thanks for the info. I would say that bag worms are ruled out as well as drought. If anything that side might get more light than the thriving side. if I didn't make it clear, the pictures are of opposing sides of the same plants. I cannot speak to drainage or voles. It just seems odd that these bushes were doing well on both sides until recently (I'd have to ask my daughter to pin down the exact time.) Does any of this help narrow down the problem? Also, might removing every other bush help?
We do not know what is on the other side of the trees. Please send photos of the location, showing the whole trees, around the base, and the browning of foliage so we can see what you may be dealing with.