Root crops and tubers both grow underground. These plants have been providing humans with nutritious food for thousands of years. Roots and tubers look alike, but there are differences.
What are Roots and Tubers?
A root is a compact, often enlarged storage organ with hairy stems that develops from root tissue. A tuber is also a root. More specifically, it's an enlarged storage organ, but it develops from elongated stem tissue, or rhizome. So a tuber is a root crop, but a plant can be a root and not a tuber.
Carrots and cassava are root vegetable crops. Potatoes, sweet potatoes and yams, on the other hand, are edible tuber crops. There are differences in the way edible root crops, or plants, grow and the way edible tubers grow.
The reason root vegetables and edible tubers contain so many starchy nutrients is because these are the parts of the plants that fuel the growth of the plant above ground. While most vegetables grow above ground, root and tuber vegetables are the part of the plant that grows below the soil or on the soil surface.
Tubers as Plants
Tubers grow on underground rhizomes that run horizontally just below the soil or at the soil surface. The tuber itself is simply a swollen section of these rhizomes. Nutrients collect in these swollen chunks. Their purpose is to store nutrients for the plants in order to generate healthy new growth each spring.
Tubers aren't like what most people think of as traditional plants with a root. There's no compact root producing an above-ground plant. Instead, enlarged rhizomes spread horizontally, and along these stems are nodes or eyes.
These nodes may grow up through the surface as shoots and stems or down into the soil like roots. Unlike root plants, you can cut tubers apart and replant them and they'll grow.
The Function of Roots
What we think of as root vegetables grow like many common vegetables. They have foliage above ground and a root, usually a hairy root, below ground. Roots that aren't also tubers don't have those horizontal rhizomes.
But, root vegetables often have the same nodules and growths on them that tuber vegetables have. That's why it's hard to tell the difference between these vegetables once they're harvested.
Root vegetables differ from vegetables grown above ground only in the part of the plant that's eaten. Sometimes, plant roots and foliage are both edible. Beets and beet greens are a good example.
Tubers That are Edible
The white potato is the most common tuber that most Americans eat. Another tuber is the Jerusalem artichoke. Also called a sunchoke, this plant is often eaten raw. It can also be boiled or roasted similarly to potatoes.
Sweet potatoes aren't closely related to white potatoes, but they're tubers, as are yams. Sweet potatoes, native to America, grow in different colors, including orange, white, yellow and red. Yams, which aren't sweet potatoes, are native to Africa. They're very large and have white flesh and dark skin.
Cassava is another edible tuber. It's grown in tropical areas and is an important food starch in many parts of the tropical world. It has a short shelf life, however, which makes it hard to grow commercially.
Tubers provide the starch to keep the plants growing, and this is why tubers are important sources of starch in many parts of the world.
Edible Root Crops
Carrots, with their hairy stems, are a good example of a root vegetable. They look like a plant root. The part of the carrot plant that we eat grows underground, while carrot greens are the feathery foliage that grows above ground. Carrots, like other root vegetables, contain nutrients and starches for growing the above-ground plant.
Carrots are just one type of edible root vegetable. Beets, parsnips and turnips are other good examples. All of these vegetables, along with edible tubers, are full of nutritious starch that provides energy for both plants and humans.