Cutting mature hemlock to grow more dense

[dbooksta]

I'm in southeast PA, and I have a row of mature (20+ years old) hemlocks that I want to train to form more of a privacy screen. The branches have gotten too long so they are overhanging the lawn, and lower branches have naturally died off. Is there any way to prune or cut these to stimulate more dense growth lower down and closer to the trunks?

 

[billb]

I'd cut them down and start over with one of the newer dwarfed types that don't try to be an 80 foot tree.
If what you want is a hedge.

My father planted two 100 foot rows of hemlocks for privacy/street noise abatement 40 years ago. He kept them pruned down to a manageable size until about 1990 or so when he started struggling with arthritis. He died in 2004. I was tasked with doing something with the neglected trees. One row we just cut down. The row against the street we cut the top third off bringing them down to about 12 -15 feet. The one top is now 2/3/4/5 tops that need to be topped repeatedly and they have tried to get wider requiring constantly pruning back. Like every Spring and every Fall. and the last couple of years battle the woolley adelgids and gypsy moth caterpillars that have destroyed some others ( along with the drought last year ) . I'm about ready to just remove them and replace them with something else that is hopefully less work ( not arborvitae !!!) but dunno what yet. I could take a bunch of cuttings and clone them.
Not one of them has sprouted any new growth along the trunk like yews do. I don't believe they do.

 

[dbooksta]

Yeah, I used a very aggressive insecticide a few years ago for the adelgids and fortunately haven't seen those since.

I don't mind pruning. How hard back can you cut the main branches before they will fail to sprout?

 

[billb]

I've cut all the way in to the last pair of stems with green growth, but usually don't go quite that far as it looks a bit radical. Any further than that and the branch is dead. Also not every branch on the tree cut back that much. About 30-40% a year. Seems to sprout any where there are still leaves showing. Just never on bare branch. So I cut a little bit selectively. I'm losing a weekend or two to it every year. And getting tired of it.
They're kind of like a pool. Do a little bit of checking and maintain every day and it almost never becomes a big project. Don't prune them for 15 years and now it's a big task. Most if not all hedges are that way it seems.