I have two chindo viburnum plants that are about 8 years old. They have handled past winters pretty well, except for these last two. The latest cold snap knocked off most of their leaves. I was assuming they were probably dead, and in looking for dead branches I actually snapped off an older branch at the base of the plant. The wood at the bottom of the branch was dry and brittle, but the smaller branches near the top were still supple and had new leaf buds. Is the plant dying slowly from the ground up, or are the healthy Chindo branches brittle at the bottom?
This viburnum is rated as a zone 7 species. Assuming you are in zone 7, then in most cases the plants should be tolerate the low temperatures of your area. However, cold snaps can wreak havoc with plants and low temperature damage can occur even in the zone rated for your plants. Another aspect is microclimate; areas on your property that are a bit warmer or colder than the designated zone. Cold injury is typically evidenced on the upper portions of a plant (most recent growth) but a condition known as bark split (due to low temps) can occur on older portions. Once growth resumes in spring you will realize the extent of the injury.