Oops, it doesn't look like 'throw away your lettuce day' is a national day..

Other days

kale

Kale Day
prosecco

Prosecco Day
hannah

Hannah Day
gum

Gum Day
fiancee

Fiancee Day
boba

Boba Day
self appreciation

Self Appreciation Day
first love

First Love Day
martini

Martini Day
lisp

Lisp Day