Leylandii grrrrr....
 

I have decided to fill my green waste bin with Leylandii clippings each
fortnight till I have made a dent in the '@:!!!? hedge.
Grown by my (previous) neighbour and left to grow, trouble is it takes
years to make itself presentable after pruning.
C'mon someone make a virus / pest that attacks it and make yourself a
billionaire!
Rog

http://rog.pynguins.com/content/item/beans

My side of my neighbours' leylandii is at its most presentable immediately after pruning, though if the top has been lowered it might take a few months for the top to be restored. If it doesn't make itself presentable fairly quickly, you've probably cut it back too far. If you remove the green surface and expose the brown underneath, it doesn't grow back.