What is the meaning of [Salad days]

The days of one’s youthful inexperience.

From Shakespeare’s Anthony and Cleopatra, 1606:

CLEOPATRA: My salad days,
When I was green in judgment: cold in blood,
To say as I said then! But, come, away;
Get me ink and paper:
He shall have every day a several greeting,
Or I’ll unpeople Egypt.