Very tolerant of pruning, within limits. Makes an excellent sheared hedge or even topiary. But do you want to maintain a 12' hedge?

Another thing is that this fast grower is pretty much always rootbound, growers apparently seldom keeping it potted on in a timely manner (a pandemic problem not limited to this particular plant, but all the more likely with subjects such as this that grow like weeds). A sheared hedge is less likely to have specimens with knotted roots go over under wet snow, but might still be subject to girdling in time.

bboy, ken:
The plan was indeed to have a ladder (perhaps longer than 8') and go at it twice a year :) I was hoping that once they lost their leader they would stop getting taller and only get denser (and fill out, so to speak).

The expense of replacing close to 20 trees is an issue - although it sounds like the cost and effort of maintenance of a hedge would be more in the long run?

How does the Leyland Cypress sprout new leaders? Do new branches sprout from below the pruning cut and grow upwards? If the cut happens just above a lateral branch, would the branch turn upwards and emerge as a new leader with time?

New leaders will have to be trained to become dominant. There will likely be many competing 'leaders' following any top cut.

"and go at it twice a year :)"

If you want it to look neat and avoid brown patches and/or steadily increasing size, it needs trimming 5 or 6 times a year.

Resin

Trimming a 12ft with a ladder would def. be a longterm pain. I would rent/buy one of those mini cherry pickers

Thank you for your advice. 5 to 6 times a year sounds like a lot, so I may have to rethink this plan. I'll probably try it for a year or two to see how far I get.

dsieber: That is an interesting idea, thanks!

You'll get on the ladder maybe 3x and that'll be it if your wife has any sense.

You'll want shears on a pole, if you think you really are serious about it. Echo makes power pole shears and mini pole chain saws, such as those in AM Leonard's catalogue.

Not cheap, but way cheaper than falling and bonking your head on the fence or breaking your arm and the wife mad at you for two months, or falling and landing on the saw and your wife mad at you for five months, or falling and...

Dan

I tried to find a link for the mini cherrypicker I saw but check out GENIE SCISSOR LIFTS may be even better for a confined space between hedge an fence.

Why 12'?
Why not 8'?

We have planted Leyland Cypress trees about 6 feet apart on
the boarder of our land. My husband cut the main top branch
of some so that newer ones would catch up in height. Has
he now ruined the chance of these trees growing any taller?

"Has he now ruined the chance of these trees growing any taller?"

No, but he has pretty much ruined the chance of them ever having a good shape; they will produce multiple new replacement leaders at the top, leading to forked trunks liable to split in snow or gales, if they are allowed to grow much larger. They will now either need to be kept permanently trimmed at around that height, or pruned very carefully to ensure they only develop a single new leader.

Resin

I am the OP. We topped our trees at the 11' mark and like pineresin said, multiple subordinate branches will compete to become the new leader, leading to a hydra look.

If the cut was made so that there was a topmost branch very close to the cut, it may take over and become a leader - I experimented with doing that for half the trees I topped, and it has worked well.

We had a beautiful row of cypress giving us nice privacy between our yard and the neighbors. The neighbor complained about how 'shaded' our trees made their yard so we lopped of the tops, we did not know they would not grow back. Biggest mistake ever. It is so much more work constantly trimming them to keep them in shape. It looks ugly too. A big, fat thick hedge when it should look lofty with nicely pointed tops. They are also deformed, with branches jutting out from the sides and overgrowth on the top. Horrible. I want to start all over, but we've had these for 10 years... We are going to try training a new leader before starting all over again. Our question is, how far down the trunk would you trim off any competing leaders?

cd ... you ought to start your own post.. and check the box for replies to come to your email.. rather than the original guys ...

suck it up.. and get rid of your nightmare ... you know that is what you should do.. so just do it...

ken

we planted some Leyland cypress as a screen. the land next to ours had someone move in, with in a few feet of our fence. She ( the neighbor ) wanted some privacy as we did. We planted 15 feet from the fence. But she got a new boy friend who sprayed something on the trees, the limbs he sprayed died. They are three yrs old now he sprayed them a yr ago. my question is can I cut the trees down close to ground and them sprout back?

start trimming the leylands once they hit 8 feet. They ALWAYS keep growing. If you wait too long the bottoms will die. Use a polesaw (8" Kobalt is fantastic) to make the cutting easy. You COULD take out every other one and plant a replacement Giant Green in place of the removed one ... Yes, best to never plant them in first place. Giant Green Arborvitae might be better, but it will also need trimming.