This is a really hard ? to answer, as science is not know all the reasons why. It is a mass of new buds that never really do anything, but pile up on top of each other to make amoazing grain patterns. Its cuased by many thing, from everything I've read the just can't really pin point it. Adventous buds can lie dormant for many years before being called upon in time of need(some type of big stress on the tree, lost large limb in storm for example) I think this is why we see trees that send out adventous buds are the ones making all the burls. As pine, and such hardly ever make burls ( oaks are middle of the road so they will sometimes make burls, maples one of the easiest to send out adventous buds is the tree that make the most burls) not sure what the link is but there must be one. Not sure if I have helped or made it more confusing for you, They are the pearl of the woods, Victor