Hand-harvestable-only crops like lettuce and tomatoes. Basically the CA Central Valley.
How do they actually taste? I know they're in the artichoke family, but I've never actually dug one up or whatever.
Perhaps if they could be blended and used as a base for bread or cakes, but I have no idea if they're safe in large quantities.
Good point, for most foraged stuff you definitely don't want it to make up more than a certain percentage of your diet. Not only because of the plants themselves, but also because it's hard to know how much heavy metals and other toxins they absorb. You should be fine treating it as a normal vegetable because it's known to be safe in those quantities, I just wouldn't eat it every meal for a week.