I cut back my old Penstemon blooming stems as they finish, down to any side growth.

Some people leave the old Buddleja blooms (my mom), and some cut them off (me). I haven't seen any lack of production from those that don't have the old blooms removed, though.

I don't have crape myrtles, but I know they bloom on new wood. They should be pruned in winter or early spring. Not sure if you would be ok doing that now, though. Someone with more experience will post soon.

You might want to look into getting the Sunset Western Garden Book. It has tons of info about plants, including pruning. :)

Brenda

Crape myrtles are blooming right now. I have mine cut back on the top each winter to encourage new branches for more flowers. It's ok to cut now as they are tough.

I dead head penstemon all year and buddleia will they are flowering as the flowers fade.

Penny

I dead head the Buddliea as needed, then cut back to a few strong 12" canes in early spring.

I deadhead the Buddilea and both Penstemons to encourage more flowers. Crepe Myrtles are on the list for next year.