Cannabis could be eaten as a vegetable in antiquity.

But not a very appetising one. In Palatine Anthology 11.325, the poet Automedon compares it to cabbage that has gone yellow with age:

Yesterday I dined on a goat’s foot, and a ten-day-old
quince-coloured cabbage stalk, like cannabis.
I won't name the one who invited me. He’s grouchy,
and I’m scared he might invite me back again.