“Root vegetables” is a relatively generic description of vegetables, including starchy ones, that grow underground. Many plants that produce edible roots also have other culinary uses. For instance, turnips, a classic root vegetable, are famous not only for their underground portion but also for the turnip greens, which are a popular food in the Southern United States.
To make matters confusing, root vegetables aren’t always roots. Some vegetables that people eat are actually bulbs instead, like onions, garlic and shallots. Many people may differentiate onions and garlic as more spice than vegetable, but they are often grouped in the "root vegetable" category.
Potatoes are usually labeled as tubers, and again, most people think of them as more of a starch than a vegetable. Despite that, they are a part of the this category. Plenty of other vegetables fall into this group as well.
Other vegetables often included in this group are sweet potatoes, carrots, beets, parsnips, jicama, leeks, and Jerusalem artichokes, to name just a few. Sometimes, certain ones form a major part of a culture’s diet. This is certainly true of roots like yams, taro, and potatoes in certain parts of the world.
Other times, underground vegetables are important to a culture but are used to flavor main meals or as an important accessory to dishes. For instance, carrots are often served as a side dish, but wouldn’t likely be used as a main food. Ginger, on the other hand, which is a rhizome, is delicious when added as a spice, and many cultures enjoy either fresh ginger, pickled thin slices of ginger, or dried powder ginger to flavor foods.
Due to the tremendous variety expressed by the term root vegetables, it may be difficult to know what the term refers to in most conversations. In classic American cooking, people may specifically mean things like carrots, leeks, potatoes, parsnips, and onions, and certainly not things like peanuts, though these are sometimes called groundnuts. One thing that can be generalized about most “underground” foods is that they require especially good washing practices.
Since many foods are grown in manure, dirt, and/or compost, cooks will really want to take their time cleaning root vegetables. They should invest in a good scrubbing brush designed for vegetables to thoroughly clean things like carrots, leeks, beets, or potatoes. Cooks may notice small pebbles imbedded in larger vegetables, which should be cut out during cleaning. Some people prefer to peel things like potatoes or carrots to avoid scrubbing them, but others say it’s much more nutritious to leave the skin intact whenever possible.