My blackberries! I didn't kill them! We moved into our house last spring and I was delighted to find four little blackberry bushes, didn't get too many berries, but enough to much on, anyway. I didn't prune at all during the summer, so that could be it. Well, when my husband and I cleaned up the yard in the fall I found a gigantic mass of spikey vines. The plants had doubled, if not tripled in size, and where the vines touched the ground they'd put out roots. I pulled them all out and pruned the plants back to what they looked like the spring before.
During the rest of the fall I would look out at my forlorn blackberry sticks with their brown leaves that never did drop and worry and worry that I'd killed them. Well, spring came, and the forlorn black sticks began turning a rich reddish brown, which my husband assured me was a good sign. I had no choice but to wait.
Then, finally, a week ago, I discovered why it's called an invasive weed! All along the ground there's baby blackberry bushes popping up! HURRAH! At this point I'm considering just cutting down the old stocks that bore fruit last year and allowing the new babies to grow, what do you all think? I'm also praying the neighbors don't get mad if the blackberries decide to migrate into their lawn... they were planted right on the property line to begin with.