Answer: Most garden hydrangeas produce flowers on new shoots which develop on old wood. The best time to prune is in very early spring, just as the leaf buds begin to swell on the stems. At this time, cut everything back to about 18" high. Remove the oldest (grayest) canes as these are usually non-productive. Then prune the remaining canes to an outward facing bud, in the direction you want the new growth to take. The shoots that develop from these pruned canes will produce flowers if you hydrangeas get adequate water and morning sunshine.
Best wishes with your garden!
Q&A Library Searching Tips