A eucalyptus leaf is a vegan food item with some non-nutritional uses.
Eating a non-cursed one will cure sickness and nausea. It can also be applied as a whistle, and acts as a magic whistle if blessed and a tin whistle otherwise. There is a 2% chance that a blessed eucalyptus leaf will become unblessed after being used as a whistle.
A user has suggested improving this page or section as follows:
"In 3.6 there may be some trees in Big Room or Medusa's Island, so the 29.4% figure needs to be recalculated."
Eucalyptus leaves are fairly rare, making up only 0.3% of all food items. Players have roughly a 29.4% chance of finding any at Medusa's island or above, in the Gnomish Mines, or Sokoban, excluding the quest and all death drops. There is a 4.7% chance of some in Sokoban. Minetown has a 7.2% chance of eucalyptus leaves, mostly due to a 35.1% chance from kicking and then cutting down both trees in Bustling Town. Barbarians, Monks, Priests, and Rangers are nearly guaranteed to obtain some from the trees in their quest home levels. Pacifists should know that eucalyptus leaves are not generated in any monster's inventory, as opposed to death drops.
The effect of using a eucalyptus leaf as a magic whistle seems to be based on the Australian 1960s TV show Skippy the Bush Kangaroo, which had a recognizable theme call played on a eucalyptus leaf. Skippy came bounding through the bush to whoever played the eucalyptus leaf.