Plant a Sapling // Fully-Grown Treefolk

Search your library for a basic land card, reveal it, put it into your hand, then shuffle this spell into its owner's library transformed. (For playtesting purposes, put it into its sleeve upside down.) (You can't cast this face unless it's been transformed by the front face.)
Fully-Grown Treefolk's power and toughness are each equal to the number of lands you control.