Not really, but if the arch is to be part of a path or an entrance, then I can imagine that the trees should be 2 people apart. That is, a path that is comfortable for at least 2 people to walk through. How high? Although I don't have the exact heights of hornbeams, these are tall trees -- well over 20 feet, so I can imagine it would be easy to train branches into an arch shape. You can get ready made arch forms and simply train the branches on it.

Ok, 'pleaching'...'hornbeams'... be back after a little research. Sounds like fun. I'm wanting to create a living arch in my back yard area as well. Jim

Jim, Topiaries of this form need not be limited to hornbeams. The other plant most commonly used are yews. Do your research on that plant too. It's evergreen, very forgiving should you make a mistake. It is quite ideal for creating garden rooms.

Ianna