Blackberry Vine is one of the vines added by the Soul Forest Mod. It is a vine that contains blackberries which have a dark-red/purple colour. The Blackberry Vine, as all the other vines, isn't climable.
To harvest all of the vines you will need a berrycollector.
The most important recipe for most of the vines, is the crafting of a Bushel. You can craft a Blackberry Bushel with 9x Blackberry Vines. Once you've got the bushel, you can't re-claim the vines.
The main purpose of the vines, is the crafting of the newly added food-types by the Soul Forest Mod. You can't craft the vines directly into food, you will first need to craft the vines into bushels as described above.
With Blackberry Bushel you can only create a Blackberry Crumble.
The Blackberry Vine can be used as a farming material, if you would make a big "vine-farm" you can easily harvest more then enough of this vine to make a lot of Blackberry Crumbles. But ofcourse it can also be used to decorate the walls.