Answer: Since the boxwoods are well rooted, I think I'd take a chance that they will grow back when you prune them back severely. I believe they will. If they don't, you'll need to dig them out and the root systems will be quite extensive. There's really nothing that grows as well as boxwoods in your area, and considering you'd have a real challenge getting the old plants out, let's hope they rebound after pruning and fill in within a few years.
Best wishes with your garden.
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