Ashes alone apparently are bad for the growth of trees.
However, with the right set up, and some botany stuff that I do not understand, these bio urns use the ashes to nourish the growth of any type of tree of your choosing, hence why you may have also heard of these referenced as "tree urns".
So in a round about way, you could think of these as urns that turn you into a tree upon your inevitable demise, and live forever!
The bio urn seen here is from Eternitrees, and allows you to bury ashes of a loved one and grow a tree of any kind. Upon ordering, you select from a long list of tree types.
Last I checked, there were 16 types of trees to choose from. Future generations will be able to commemorate the passing with a living and tangible thing.
A unique way to mourn the passing of a loved one for the current generation as well as future generations.
The urn itself is biodegradable.