On the campus we have many places in which edible things are growing and which are available to anyone on campus or anyone who takes a walk through the campus. We have lettuces, kale, spinach, collards, radishes, all manner of herbs, just about anything you can think of.
But people get so used to picking that sometimes a planting bed that looks like vegetable greens is really flowers, gets picked. So a sign is necessary.
One of our edible beds, actually 5 beds from front to back here.
And a not edible bed which needed a sign because the green looks lettuce-y