I've been growing the BB pictured below for almost 30 yrs, first in OH, and in AL for the past 7 yrs, and would not try what you described. Prone to suddenly dying for undetermined reasons. Taking cuttings first would be a much more reliable plan. Put the cuttings in the ground where you want the new shrub. I started with 1 plant in OH, and have been using it to make new BB's every time I moved, including moving to AL. I always try to have at least 3 of them, in various locations, because of their tendency to die. I would probably wait until they've leafed out well in the spring because BB's have a reputation for resenting fall pruning, as you mentioned, and because spring cuttings have been almost fail-free while those done later in the year have shown a lower success rate. I've never used any root hormone for this plant (I don't own any.)
I don't know my plants' name, just that it's one that doesn't cause sprouts. It's a stiffly upright shrub, flower shown below. I've never once found a volunteer BB in any of the yards where I've had them. IDK how tall it can get, I trim them pretty heavily in the spring, and later as needed, so they don't get taller than me (up until about this time of year, then leave them alone.)
I can't tell from your pic if yours is the same kind I have or not.
My mom got one, blue chips I think, that has a droopy overall appearance, and is a mess, now a clump, from all of the sprouts. I would stay away from that one, or any with those droopy flowers.
The next step after attracting adults to your garden for nectar, if interested, is offering some host plants for their caterpillars to eat.
http://www.dallasbutterflies.c...
BB is always popular with butterflies, but Lantana is even more so.
