The blue spots on this close up of a eucalyptus leaf are stomata, or pores. Through these many miniscule openings, the eucalyptus leaf takes in carbon dixoide and “exhales” oxygen. The stomata also function like pixels on a computer screen, creating a bluish tinge in the leaf’s appearance.
Young leaves are more rounded and have a slightly thicker wax coating for protection from moisture loss. This lush foliage contains more nutrients than larger, older leaves, which is probably why koalas prefer them.
The long, narrow shape of adult eucalyptus leaves reduces the amount of surface area exposed, thereby helping the tree avoid high moisture loss under the intense sun.