Posted: 18/04/2015 at 09:05
We are just doing exactly the same. Raising by about 6 inches. I've lifted all the herbaceous stuff and small shrubs but have removed lower branches from a fir tree and are hoping for the best.
we did the same last year with another border but all the big stuff was at the back where the soil was higher so they only had an inch or two of extra soil and have been fine.