By Michel
Hertfordshire,
United Kingdom 
On part of one boundary I have a line of half a dozen leylandis 50 to 60 feet tall, about 50 years old, where I would prefer a hedge 8 to 10 feet tall. If I cut them down to about that height, will they fill in as a hedge in a year or two, or will they always look like a line of mutilated cut-down mature trees?
17 May, 2011
Answers
If your trees are so tall and you wish to reduce them why not get rid of them completely and plant a more attractive hedge.
Leylandii cause too many arguments between neighbours as they rob so much light and give very little.
If removing the trees is not an option, you could cut down the trees to the height you want, ring the bark at the bottom to help kill them, fix wires between the trees so you could plant various climbers that you like. You would soon have a much more attractive hedge which may in time attract nesting birds.
17 May, 2011
Actually Allotmentman the birds are more than happy to nest in Leylandii. But I agree would get rid of completely and grow a native hedge, something like a mix of hawthorn, blackthorn, beech and a prunus.
17 May, 2011
Thanks for the comments. Removing them is one of the options, but before doing so I wondered if severely reducing the height would provide a short cut to a hedge of reasonable height. In their position, well away from houses, they cause no light problems with neighbours.
17 May, 2011
Depends what the bit you'd be keeping looks like now as it won't get any better.
17 May, 2011
No it wont, if it is a trunk or brown branches it will remain that way.
17 May, 2011
trouble is you may cut them down to 8-10 feet high but they will still be 20-25 feet wide and to my mind look silly and as moongrower sais if you cut them hedge shape ie say 3-4 feet wide they willpossibly die at worst or look brown ang ugly for ever so id definatly maybe take all but one in if your garden is that big or cut the lot down personaly .
18 May, 2011
I agree with NP. at that height, the width at 8- 10' must be fairly wide. Look inside to see how far back the green goes. But then looking at the other options. Have a go, get them chopped to desired height. if you don't like it, get them removed all together.
18 May, 2011
id lose them as theres so much more interesting stunning plants or trees that could go wear they are .
18 May, 2011
What are the trees like on the lower 8-10 feet at the moment Michel? If that portion is brown and dead it won't regrow. If the bottom 10 feet or so is still green & looks OK you could probably chop the tops off the trees and end up with a hedge.
The trees will immediately start growing new tops, so you'll need to get someone in to trim the hedge regularly (every year or two, at a guess)
17 May, 2011