Arbor vitae-bottom growth
I planted arbor vitae two years ago. They were full and bushy when planted. Today, the bottoms have lost a lot of foliage and are beginning to brown. Is there a way to encourage growth at the bottom? My soil has high clay content, which I know is not ideal. During the summer I use a drip irrigation for 30-40 minutes each day. Please see attached photo. Thank you in advance for your help!
Multnomah County Oregon trees and shrubs
Here is information from other states that might be of help regarding the cause and remedy for the damage you mentioned:
The arborvitae have probably suffered winter damage. The brown leaves will not recover but adjacent living tissue (if any) may produce new leaves. The degree of recovery depends upon the extent of the damage which may not be obvious until late spring or early summer. Delay pruning until then. When (if) new growth develops you can cut off the dead leaves or branches. To reduce winter damage in the future, mulch the arborvitae and provide plenty of water, especially in the fall, Avoid pruning in late summer. If the problem persists provide winter protection. Here is a link to more information: http://www.extension.umn.edu/distribution/horticulture/DG1411.html Protecting Trees and Shrubs Against Winter Damage Yes, you can remove the brown tissues in the spring.
For information on how to prune evergreens successfully, please see CSU Garden Notes #617 on pruning evergreens: http://www.ext.colostate.edu/mg/Gardennotes/617.html
It is best to cut the shrub to a side shoot that is growing. Cutting too far into the shrub will not stimulate new growth.
These resources should be of help to you.