There has been some debate over the years as to exactly which
   circumstances will trigger a Compost.  The main issue arises because
   it's possible for the card to be black in the graveyard but not when
   it's in the hand, or on the battlefield; it's also possible for the card
   to be black in the hand or on the battlefield but not in the graveyard.
   Under the current regime, the trigger event is now never considered
   to be a leaves-the-battlefield trigger.  Consequently, it's the color
   of the card once it gets to the graveyard that matters when determining
   whether Compost triggers.

     Compost  {1}{G}  Enchantment
   / Whenever a black card is put into an opponent's graveyard from
     anywhere, you may draw a card.