Saplings are young Trees. They require dirt under them and light (Either Sunlight or Torches) to grow. They won't grow if there is no room above them. After a few days Saplings turn into Trees which can then be harvested for Logs and Saplings. Bone Meal can be used on a Sapling to cause it to instantly grow into a Tree. There are four types of Saplings: Oak, Pine, Birch and Jungle.