Hopefully there will be someone out there who will think there is an obvious answer to my problem.
We planted a hornbeam hedge with 60-90cm plants in March 2007, the tops of these were cut at the time (as instructed) and they were planted with Rootgrow. This Winter just gone I cut the tops out again to help them bush at the bottom but considering this is coming up to their third Summer they do not seem to have done much growing.
The garden centre that I bought them from has pictures on their website of a hornbeam hedge in years 1, 2 and 3 and year 3s hedge is much thicker and taller than mine.
Does anyone have any ideas as to why this might be?!