Large burls on fruitless mulberry tree
For 50 years the fruitless mulberry limbs have been cut off in the fall, back to their central stem. Now there are huge burls ( 12" to 18" ) which look terrible in the winter months. Can these huge burls be cut off completely so that new growth will be at the end of the limb?
Yes, you can prune off the knobs to just below. Observe the multiple sprouts in the spring and let them grow out a couple of feet, then thin the excessive sprouts, selecting two or three in the best placement to allow to grow and become new scaffold branches.
In time and with diligent follow up pruning, you can restructure the tree. There will be some concern for decay in the large cut surfaces. Eventually that could become serious wood rot that will weaken the structure and allow breakage.
That type of assessment and follow up is best addressed by a local arborist.