Stems come in all shapes and sizes, and some of them are eminently edible. Take the potato, (which I can do only if I add lots of butter.) The potato is actually a “stem tuber,” a stem that stores energy in the form of carbohydrates.
Potatoes differ from “root tubers” such as carrots, radishes, and sweet potatoes. The “stem-ness” of the potato is evident when you look into its eyes. The eyes are actually axillary buds, just like you find on the nodes of above-ground stems. When the eyes grow out, they form shoots, which then branch and sprout leaves. Cut up a potato and plant pieces that have eyes, and each one can grow into a new potato plant. Root tubers, on the other hand, are for storing energy, and have no buds.
A potato plant also produces flowers that range from white to pink and red to blue and purple. Some varieties produce green fruits about an inch in diameter. The fruits are poisonous, which is not too surprising since the potato is a member of the Solanaceae family, which includes deadly nightshade, henbane, mandrake, and other toxic “witches’ weeds.”