You PLANT them??? LOL
Our entire back yard would be taken over in one summer if we did not hack them back every week. I bet our house would be covered after 2 years.
They grow new branches every year to bear fruit, so cutting them back is probably a good thing. If you insist on "growing" them.
Seriously, you can walk down almost any street around here and just eat as you go when the blackberries get ripe.