Artichokes can’t handle reactive cookware such as iron or aluminum. Unless your iron pot is enameled you should avoid using these types of pans as they will turn the artichokes an ugly green-gray color.
Regardless of the pot of choice, add 1 tsp lemon juice to cooking water to help these edible thistles retain a healthy color. Another option to prevent discoloration is to rub all the leaves with a lemon.
Artichokes are done when the stem can be easily pierced with a knife or fork.
