.............I've dealt with Sumac in a limited space. When the root suckers first appeared I was going to dig them up and pot them for planting elsewhere. In the end, however, I decided to leave them and see what happened. The photo says it all. About the only thing not in view is a large clump of 'Fairytale Pink' Daylilies planted just behind the Catmint. I cut them back a week ago to get a fresh clump of foliage and possible rebloom.
The 'Orange Rocket' Barberry took some effort to attain the fairly tight shape you see in the photo. Left to its own devices the stems tend to splay outward... seriously affecting a "columnar" look. I acquired a 6 inch wide, 4 foot tall metal trellis... placed it behind the plant and wired it in several places too keep stems growing straight up. It looked a bit constricted for a while... but new growth hides the metal "corset" and the plant now has a good columnar look.