Board Thread:Dark Souls II/@comment-24679176-20140314222208/@comment-24677852-20140314223132

I believe the seed of the giant starting item is what you need to activate those. There is also one near Cardinal tower. I am unsure of whether or not they can be acquired somewhere else in the game as I am pretty far (lvl 81) and still have not found one. Until you find one that is a dead end. Try going another direction, there are many other routes you can take to progress.