Can You Speak Tree Language? New York City Does

Created by artist Kate Holten, the New York City Tree Alphabet lets anyone send hidden messages in tree language. You can also download it as a font.
A tentative version of Holten’s new Tree Alphabet was shared across the Parks Department for months, as groups across the system chimed in on which trees should stand for which letters–a more complicated idea than one might think, given that the Parks Department is particular about the species it wants planted.
*cries in Ogham*