Closeup at the base of a hydrangea serrata that had never been pruned in photo 1. Photo 2 shows the same view after removing nearly 70% of the canes, many of which were dead. This is the appropriate density for hydrangeas. Pruning was done mid-summer because it was the only visit of the season, however, the optimal time to do this type of pruning on most hydrangeas is early spring before the leaves form. We start by removing dead canes and then remove some of the older less productive canes and leaving the younger more productive canes.