My friend called me to tell me that he was getting rid of his (30 or so) Thornless blackberry plants. Of course, I rushed over, dug them all up, and brought them home. I planted them all in a sunny spot along a trellis. Do I really need to cut them down to a few inches tall or is there an okay chance theyll survive if I leave them as tall, mature plants? I thoroughly watered them and heavily mulched them. I would rather not cut them down if at all possible, but I know it would probably help them.