We foolishly planted 3 potentially large trees very close to one
another on a little hill behind our water garden. They all look just
wonderful now, 5 years later.

But it's obvious that very soon they will be growing into one another
and dwarfing the pond and hill. If possible, I'd like to keep them
just the size they are, and would need to act this year before they
become too large to easily prune.

They a 1 Norway spruce, about 10 feet tall
1 Eastern hemlock, about 12 feet tall
1 Western blue pine, about 15 feet tall

They are in a triangle with each trunk about 10 feet from the others.
I know, I know, we were idiots.

But all three trees are thriving, and we love the way they look now.

Is it possible to "bonsai" them to keep them this size? Should we
leave this to the pros, or could you point us at a good book?

Thanks,
jon