What’s wrong with my plum tree?
Last year I thought it got frosted as all the ends died, but new growth came on, so I trimmed all the dead ends back to the point of new growth. This year I only have about 6 branches that had any new growth at all and all the branches from last year had no growth. It was not frost, as the leaf buds did not even swell to begin opening. Do I cut it back to the stump and basically let the roots start a new tree? Or is there a less severe trimming I could do to bring it back? I did get some fruit on it years ago, but lost its companion tree to frost about 5 years ago and it has simply been ornamental since then.
Your tree likely did not survive this severe pruning.
Your Plum Tree was likely a grafted tree. The fruit tree is grafted unto root stock of a different cultivator.
The growth your seeing is a fruit tree of some type but will not be the same tree you had.
You may want to dig up and start with a new planting this fall. Look for varieties that are cold hardy to zone 4.
Here are some links for you.