I came across the Silphium plant that went extinct around 64 AD. It is believe that emperor Nero was to have eaten the last known stalk!
It surprised me that such a valuable plant was not cultivated through agriculture.
Are there other plants that we know to have literally eaten out of existence?
You could start by reading New Lives for Ancient and Extinct Crops. I recommend the other books by Paul E. Minnis, like Famine Foods. These books are academic, though - so don’t expect a fun and accessible science journalism read.