in japan it is as common as a carrot or Celery in useage.
you can eat all parts : steamed is super.
the young leaf stalks are good in soup , but too bitter for salads
the roots and leaves are considered as a vegetable.
the roots are commonly used as a tea, (chopped or ground) and (if fresh) carry the higher % of phytochemicals called polyacetylenes, which can destroy certain bacteria and fungi.
(but you can also use the other parts in tea also)
it can help reduce blood Sugar lvls and improve carbohydrate tolerance along with a great many other things..