What rectangular bed surrounded by paving wouldn't be even more exciting with a quartet of something—anything—emphasizing its corners? But how tall should those "somethings" be? Not this tall, that's for sure.
Years ago, I'd planted a columnar hornbeam, 'Pinoccheo', at each corner, but then allowed the entire bed to have a Rip van Winkle phase, growing year by year with out any attention.
But hornbeams don't mind pruning, even at its most radical. And the trees are so hardy, you can prune whenever you get the yen. Mid-November? No problem.
'Pinoccheo' wouldn't get much taller or wider ever, but—you know me!—why let something grow on its own if you could prune it? The big question, then, is "How tall?" Or rather, how much shorter should the pruned trees be than they are now?
The easy answer is that they can't be taller than I can easily
reach. That's an eight-foot step-ladder in the picture below. If I stand on the second step from the top and prune at my eye level, I'll be cutting off the trees at roughly six-feet-plus-six-feet or twelve feet high. The tree on the front left is the first to get topped. And while I'm at it—hornbeams love drastic pruning, remember—why not cut all the side branches back to nubs, too?
Five minutes later, the front pair is completely pruned. Pruning the back pair won't take but another ten minutes; I'll leave that for another week, when I actually have another ten minutes to spare.
Twenty minutes to resize a quartet of trees for the long term. And only forty minutes per year (one cut in the Spring, another in the Fall) forever after.
Great geometry that's quick to create, and easy to maintain. No wonder hornbeams are so popular.