You can easily propagate your blackberry plants by tip layering them. Also called tip rooting – I like to do this directly into small plastic cups making it easy to verify that the roots are growing and then share with others! I reuse a plastic container and drill a few holes in the bottom for drainage. Take a blackberry (or raspberry) cane and bring it down and bury the tip about 2-3 inches into the middle of the cup. Cover with a rock on top to keep it in place. Check back in about 3 weeks to see the roots along the bottom. To separate, go back up the cane leaving at least 3 or 4 nodes of leaves and cut. Now you can transplant this to another area of your garden or simply give the cup to family or friends that want to grow their own!
Serpentine Layering is one of the two ways I propagate my blackberry and raspberry plants. Trailing varieties work best as they are easier to layer in this manner. I take a cane that easily bends down to a pot and I lay it across and bury the center of the cane. As it grows, usually about another week or 2 then I bring it over to another pot and repeat the process. The most I’ve gotten is 7 new plants from a single serpentine layered cane!