May 27, Prune snowball hydrangeas after the first frost in fall or winter. Wait for the first frost to happen in your area. This happens when the temperature reaches 32 °F (0 °C) and the ground freezes over. Snowball hydrangeas go dormant, so you can perform heavy pruning during this time. Hydrangeas flower on new wood%. Prune only after the bush has finished blooming.
Blooms appear on the previous year's growth. It is essential not to cut this prior to the arrival of spring blossoms. Sep 21, Cut back all branches to within a foot of ground level. Although you will sacrifice blooms for that year, a healthier, happier snowball bush should emerge the following season.
If you cannot bear to part with all the blooms for the entire season, consider splitting the renewal pruning over three years, removing one-third of the old canes each year. Dec 17, How to Prune Snowball Bushes. The term “snowball bush” is an example of the confusion caused by the use of common plant names based on appearance or features. Chinese viburnum (Viburnum.