I had 11 of them in the front, about 8 years old. They turned brown this winter and ALL died. I did trim them in late fall. Would that have killed them?
Certified GKH Gardening Expert
Sometimes, when the winter gets really cold, it will kill it off partially. This will usually come back and is not a reason of concern. Here is an article for more information on their care: https://www.gardeningknowhow.com/ornamental/shrubs/viburnum/viburnum-shrub.htm
Often Viburnum is pruned in late winter while it is dormant. Any growth that formed after fall pruning is unlikely to make it through the winter. Remember that pruning gives the signal to grow - send out new shoots - not desirable just before winter. There are other possible reasons for viburnum problems. One is Viburnum borer. https://www.gardeningknowhow.com/ornamental/shrubs/viburnum/controlling-viburnum-borers.htm
The other is verticillium wilt: https://www.gardeningknowhow.com/plant-problems/disease/verticillium-wilt-treatment.htm
Some Viburnum species are more susceptible than others. Here is an article that goes over Viburnum diseases and pests. Remember to always clean your pruning tools between plants (some recommend between cuts) to prevent accidental spread. Lysol wipes have shown to be effective. https://hgic.clemson.edu/factsheet/viburnum-diseases-insect-pests/