The term "root vegetable" refers to a broad category of plants that grow underground, such as potatoes, parsnips, and turnips. While all root vegetables may appear to be the same, there is a lot going on beneath the soil that distinguishes them. Tubers and rhizomes are two types of root vegetables that are frequently confused.
What Are Tubers?
Stem tubers, also known as true tubers, are underground bulbous modified stems. The tuber grows underground to store nutrients for winter survival and reproduction for future growing seasons. Stolons, which are new stem-like offshoots, connect underground tubers to the original stem. A stem tuber has leafy plants, a high starch content, and a tendency to grow near the soil's surface. Tubers that are commonly consumed include potatoes, jicama, sunchokes, and yams.
Root tubers (such as sweet potatoes or cassava) are frequently misclassified as tubers, but because they have swollen roots (rather than stems), they don't meet the technical definition of a tuber.
What Is a Rhizome?
A rhizome is a type of underground plant stem that sprouts new plants from nodes on its surface. The primary function of the rhizome is to store carbohydrates and proteins so that the rhizomatous plant can survive between growing seasons. Ginger, turmeric, asparagus, lily of the valley, and canna lily are examples of rhizomatous plants.
What Is the Difference Between Tubers and Rhizomes?
Tubers and rhizomes are both modified underground plant stems that serve as storage organs, but they work in two distinct ways:
Tubers can grow in any direction, whereas rhizomes grow horizontally beneath the ground, sprouting new growth along the underground stem as they grow.
Tubers and rhizomes can both produce new plants, but they do so in slightly different ways. Tubers have nodes (often referred to as "eyes" on potato tubers) that sprout both new shoots and new roots, whereas rhizomes sprout roots at the bottom of the growth and stems at the top.
Examples of Other Root Crops
A number of underground crops are mistakenly classified as true stem tubers. Some of the plants that have been misidentified as tubers include:
Tubers de racines: Root tubers are distinguished by swollen roots that store nutrients. Sweet potatoes/batatas and cassava/manioc are two edible root tubers (root tuber). Dahlias, daylilies, peonies, cyclamen, and tuberous begonias are examples of plants that grow from tuberous roots but are not edible.
Summer and spring bulbs: Bulbs, like tubers, have swollen underground stems, but their growth patterns differ. New bulbs sprout from the base of the original bulb, whereas tubers develop buds on their surface, from which new stems sprout. Onions, shallots, and garlic are examples of edible bulbs. Daffodils, amaryllis, crocuses, tulips, cannas, gladiolus, and hyacinths are examples of inedible bulbs.
Corms: Corms, like stem tubers, have a swollen underground stem for nutrient storage, but corms have a basal plate (the flat part of the plant where the root grows) while tubers do not. Taro (also known as cocoyams or malanga), caladium (elephant ears), and freesias are examples of corms.