David Ross said:

I suggest you first identify the shrubs. Then check a pruning
book. You don't have to buy the book if you have a decent public
library nearby. Otherwise, a good nursery might let you browse
throught a copy.

I'll try to find out what they are, the neighbors don't know. Last fall I
cut several feet off the top and they have already grown taller than they
were when I cut them. Whatever they are, they are voracious growers. I
broke a twig off and stuck it in a pot, it grew a root within a week.
--
McQualude