By Lammie
Warwickshire,
United Kingdom 
Have a flat-top white hydrangea that does not flower, it grows well, 3 to 4 feet, bags of stems, last flowered 4 years ago, my mop heads do very well, could I be pruning it at the wrong time??, if it does not improve next year its in the skip. Lammie (Roy)
23 Sep, 2010
Answers
The best way to prune these for vigour is to take out a third of the stems, right down to about 6 inches, every year. Take out the oldest stems and over 3 years you wil totally rejuvenate the bush without sacrificing the flowers on the other stems.
23 Sep, 2010
Previous question
You could be pruning at the wrong time, but you haven't told us when you do prune it!. Should be pruned as growth begins in early April, and then only to remove dead flowerheads and any dead wood and dead tips to branches.
23 Sep, 2010