These large breed dogs are still mentally puppies for 2 years, but so big at just a few months, that they can wreak havoc in just a minute or two!
I have a very smart 5 month old Irish Setter and he loves fig trees. (Told you he was smart!)
I put him out to "potty" and not 2 minutes later, he had eaten the tops off of the 2 figs I was going to plant later today. Not nibbled, not just broke off, all of the tree above the soil in the pot was completely gone. Not a trace remained.
For the record, my dog Dash chases, fetches, swims, etc. all of his waking hours- me & the kids keep him playing & busy, and though that keeps him out of most trouble, he's still teething like crazy & he can destroy something in seconds.
I don't have an answer, but I wanted to share, because it's not your fault & not your boxer's fault. He'll likely grow out of it if you can keep him busy. Certainly try the hot peppers too!
Also, does anyone have a Smith or a Emalyn's Purple for sale or trade, as mine are not going to make it! I'd be thrilled with a cutting, plant, or air layer. I'm in Northern CA, near Chico, but travel down to Sacramento monthly, so anywhere near here, I could pick up. Or I could pay shipping. I promise to keep it away from Dash!