Curse of Man-Eating Trees

Enchant player.
At the beginning of enchanted player's upkeep,
that player puts a tree counter on target non-forest
land he or she controls. Lands with tree counters become 2/2 plant horror creature
forests that have "at the beginning of your end step, sacrifice target non-plant creature
you control and put a +1/+1 on this creature" and
lose all other land/creature types and abilities.
When all lands enchanted player controls are forests, sacrifice this card.