|Should Nikko blue hydrangeas be cut back in the winter/fall?|
|Nikko Blue Hydrangeas produce flowers on shoots that develop on last year's wood. It's best not to prune these shrubs until they begin to grow in the spring. As the buds begin to swell on the branches, you'll be able to tell whether or not there is winter dieback and you can prune off the dead portions of the branches. At this time you can also remove some of the oldest branches (all the way down to soil level) to help renew the plant. I typically shorten all of the branches to 18-24" to keep my hydrangeas under control. Each year they produce new flowering shoots from the 18-24 inches of old growth.
Best wishes with your landscape!