The practice of harvesting food from beneath the soil surface has sustained human populations for millennia. These subterranean plant parts are often grouped together by the public as “root vegetables,” representing a broad and diverse category of edible storage organs. Plants use these underground structures to stockpile energy in the form of starches and sugars, allowing them to survive periods of dormancy and regrow in the next season. Understanding the different biological forms these foods take offers a clearer view of their nutritional roles and how they are cultivated around the world.
How Botanists Classify Underground Edibles
Botanists separate edible underground parts into distinct categories based on which part of the plant they originate from: the root, the stem, or the leaf. The primary categories are true roots, tubers, bulbs, and rhizomes, each representing a different adaptation for energy storage.
True Roots
True roots are structures that grow directly downward and anchor the plant, with their enlargement resulting from the thickening of the primary taproot. Examples like carrots and beets are taproots, which are distinct from tuberous roots, such as the sweet potato, that are modified lateral roots swollen for food storage.
Tubers and Bulbs
Tubers are technically modified stems that grow underground, exemplified by the potato. True roots lack the nodes or “eyes” characteristic of stem tubers, which are buds capable of sprouting a new plant. Bulbs consist of layers of modified, fleshy leaves or leaf bases surrounding a short, compressed stem, as seen in onions and garlic.
Rhizomes
Rhizomes are horizontal underground stems that typically grow close to the soil surface. These structures have nodes and internodes, from which roots and shoots can emerge, allowing the plant to spread vegetatively.
A Categorized List of Common Underground Vegetables
True roots are represented by vegetables that develop from the plant’s primary root structure. Carrots and parsnips are classic taproots, valued for their high beta-carotene and slightly sweet flavor, respectively. The beet is also a taproot, often used both for its deep red color in culinary applications and its earthy flavor.
Moving to the modified stems, a prime example of a stem tuber is the common white potato, which is a staple crop worldwide recognized by the presence of small buds, or eyes, across its surface. The Jerusalem artichoke, or sunchoke, is another type of stem tuber that stores carbohydrates in the form of inulin. Sweet potatoes, while often called “yams” or “tubers,” are correctly classified as tuberous roots, characterized by their smooth skin and lack of nodes.
Bulbs are represented by the Allium family. Onions and garlic are the most frequently used examples, contributing pungent and savory flavors to dishes globally.
Rhizomes are perhaps the most flavor-intensive of the underground edibles, with both ginger and turmeric being key examples. Ginger is a widely used spice, while turmeric is known for its deep orange color and use in curries. These rhizomes store starch and aromatic oils, making them popular in both cooking and traditional medicine.
Safe Handling and Storage of Underground Produce
Because these foods grow directly in the soil, proper cleaning is necessary to remove residual dirt and potential microbes. After harvesting, most underground produce should have excess soil gently brushed off, but should not be washed unless immediately consumed. Washing can introduce moisture into small cuts or pores, accelerating decay and promoting the growth of mold.
For long-term storage, the leafy tops of true roots, such as carrots and beets, must be trimmed to within an inch of the crown, preventing the foliage from drawing moisture from the root. Most underground edibles keep best in cool, dark environments with high humidity, such as a root cellar. Temperatures are ideally maintained between 32 and 40 degrees Fahrenheit.
Potatoes should be kept in total darkness to prevent the development of solanine, which causes a green discoloration and a bitter taste. Onions and garlic, which are bulbs, require a different storage method and thrive in cooler, drier, and well-ventilated conditions.