As a general rule harder pruning will result in more vigorous growth with larger but fewer flowers.

With Annabelle I like cutting it to the ground and I get strong (but fewer) fresh stems from the base but with bigger flowers.

Guyground

if you're afraid of having a floppy plant you're definitely better off going lighter on the pruning.

Ok, maybe I am dense but I am still not getting it. If they bloom on new wood then does that not mean brand new shoots coming from the ground and all the old stems from last year just die off.

No. They bloom on new wood - stem growth that is produced this year - regardless of where on the plant it originated. Previous year's stems are typically not dead and are just as able to generate new stem growth as it is to have the new growth emerge from the root crown at ground level. Some people never prune Annabelles or other arborescens any more than to remove the old flowers :-)

Lyban,

Thats where you are mistaken the old stems don’t die off. Cut one of the stems back a bit and you’ll see green. The stems are alive. New shoots will Emerge from the stems and produce flowers.

My Annabelle is under the spot where in heavy snow years the roof dumps snow when we rake it. So in those years Annabelle needs her broken stems pruned to ground level and it is just as others have said with fewer, larger flower heads that tend to flop. The rest of the time I don’t prune because I prefer to have stiffer stems and more flowers, even if they are a bit smaller since they are still good-sized.

Ok, thank you all. I now understand. I have had Annabelle’s and paniculatas for three years now and am just starting to understand the differences and the proper upkeep.