I've grown them in just "Nature's Helper" composted pine bark (sold as a
soil amendment at Home Depot or Lowes) and they seemed to do ok (until I
moved to a new house and left them under the deck in undrained trays for six
months, lost a lot of them after that treatment.) I think the vinegar is
supposed to be something like 1/3 cup per gallon, you could probably ask
Carson Whitlow at Cyp. Haven.
-danny