I have a healthy sausage tree that is about 2 years old and has multiple branches that want to grow in all directions from a foot or two from the bottom. I'm trying to shape the tree so that it will have a main trunk. Currently I have a single branch that is about 7' tall, but I also have multiple branches coming out near the bottom of the tree.

I've tried repeatedly to cut off the lower branches, but they keep growing back. It is a very vigorous and tenacious tree (and fast growing).

How should I prune this sausage tree so it will have a single trunk? (or at least form the shape of a tree as it should with only 1 or 2 trunks.

Also, should I wait until the dormant season to prune the lower branches? Here is SW Florida, it only gets down to about 50 degrees, so all the leaves will not fall off in the winter, only some of them. This is about the closest to a dormant season it gets here.