Wow, Chris, thank you for that extremely thorough response! Of
course, I have yet more questions to ask.

Fill a container with a drain hole with sharp sand. Place it in a saucer that will hold an inch or so of water.

Interesting technique. Does this rooting technique work well with
most other plants, or specifically Butterfly Bushes?

...so I just always whack them back all the way to the ground. It seems to encourage new growth, and keep the bush from getting leggy.

I'm not sure I follow you here. During the growing season you
wouldn't just cut off the end of a branch after it's bloomed, but cut
the branch all the way back to the ground? Or are you saying don't
bother dead heading, and cut it all the way back at to the ground at
the end of the season?

I've got a 2.5' x 8' patch that's got 23 butterfly bushes of different sorts in it

Wow, amazing. I bet that's beautiful. So what's the spacing between
each plant? Eight inches or so? And how do you apply your compost?
As a compost tea, side digging each plant, or top dressing the area?

Thanks for all your insight!

-Fleemo