Elfsong is a plant that is only found in Fangorn forest. It can be used to create yellow Ent Draught, which gives the Regeneration effect. It grows in groups of 3-10 throughout Fangorn.
The plant is renewable as it will occasionally grow when bonemeal is used in Fangorn.
This flower can also be used in a regular crafting table or the player's inventory to create yellow dye, similar to other mod flowers.