Humans have evolved with a very versatile palate. Through the years they have creatively found ways to eat just about every part of the plant that exists. Not every plant can have every part of it be made edible, as some parts of some plants are toxic to humans. But almost every part of one plant or another can be made palatable to humans, and many of them are delicious.
Roots are not just the thin white strings that hang from your flower plants when you transplant them. Roots can also be carrots, radishes, yams, onions, parsnips, turnips, beets and potatoes. All of these roots can be an important part of the human diet.
While many stems are woody and fibrous, not seeming very appetizing, some plants have tender and tasty stems. Try celery, asparagus, rhubarb or bamboo shoots for some tasty stem dishes.
Leaves are one of the more popular parts of a plant to eat, as the basis for many salads is lettuce leaves. There are dozens of lettuces to eat, as well as spinach, kale and mustard greens as examples of edible leaves. There are also teas and herbal teas made of dried leaves that have been drunk for thousands of years.
One of the most obvious parts of a plant to eat is the fruit. Fruits are designed as a seed delivery system for the plant, and so they are designed by nature to be tasty to humans and other animals. From apples and cherries to cucumbers and tomatoes, fruits and vegetables are all part of the fruiting design of plants.
Seeds are the plants' way of propagating themselves, of reproduction. Luckily for us, a lot of seeds are quite tasty and nutritious. There are large seeds like walnut, peanut and dried beans, seeds that we cook like pumpkin or oats, and seeds that can be ground into flour like wheat and corn.
Many people don't think of flowers when they think of good things to eat, but there are a variety of edible flowers. Violets, squash blossoms and chives are popular flowers to eat, but also broccoli, cauliflower and artichokes are the flowers of their plant. One of the most expensive spices on the planet, saffron, is made of the stamens of a crocus flower and capers are unopened and pickled flower buds.