Although most of the world’s people consume “vegetables” daily, the word itself has no precise botanical or scientific meaning. Various vegetative (non reproductive) parts of plants are eaten as vegetables, but reproductive parts of plants such as cucumbers and tomatoes, which are technically fruits, are also consumed as “vegetables.”
Vegetative “vegetables” include the stems of celery, the tubers Irish (white) potatoes, and asparagus shoots. Other vegetables commonly consumed include roots: sweet potatoes, carrots, parsnips, and radishes, among others. Leaves eaten as vegetables include lettuce, spinach, collards, and cabbage.
Reproductive plant parts that are considered vegetables include broccoli (flower buds); cauli flower (flowers); green beans, squash, and tomatoes (fruits); and green peas and lima beans (seeds). Many more vegetables can be identified for each of those categories of reproductive parts.
The plant crops discussed here include those that are generally eaten along with meat as a part of the main course of a meal, as opposed to the fruits, which are generally sweet and are consumed as desserts. Interestingly, whereas many fruits are commonly referred to a vegetables, most foods commonly referred to as “fruits” tend also, in the strict botanical sense of the word, to be fruits.
Early humans during the Neolithic (Stone) Age were hunter-gatherers who foraged wild plants and ate them both raw and cooked. Gradually, the plants that were most useful were domesticated.
Domesticating these plants involved both the selection of superior plants and improving the conditions under which they are grown. Improvements included loosening the soil and applying various materials as fertilizers.
Nearly all the vegetable crops now cultivated are known to have been domesticated more than two thousand years ago. Knowledge about the origins of agriculture, including the domestication of plants, comes from a variety of sources.
Before the birth of Christ, the Greek botanist The ophrastus in the third century b.c.e. listed in his Peri phyton historias (also known as Historia plantarum; “Enquiry into Plants,” 1916) crops known to have been grown at that time.
A few centuries later, the Roman Pliny the Elder made similar observations. In modern times, two economic botanists summarized the accumulated knowledge relating to economic plants, including vegetable crop plants.
The Swiss Alphonse de Candolle wrote Origine des plantes cultivées (1882; origin of cultivated plants). Nikolai I. Vavilov, a Russian, gained fame as a result of his work (translated into English as The Origin, Variation, Immunity, and Breeding of Cultivated Plants, 1951).
Among the conclusions reached by Vavilov, Candolle, and others is that agriculture originated not in a single region, as previously thought, but more or less simultaneously in widely separated “centers of origin” on several of the world’s continents.
Vegetables meet the variety of nutritional needs of humans. In addition to providing varying amounts of carbohydrates, fats, and proteins, they supply needed vitamins and minerals so necessary in the diet. Also, vegetables supply the insoluble fiber, or “roughage,” that is essentail in maintaining intestinal regularity and preventing colon cancer.
The objective is to harvest these plant parts soon after carbohydrates and other nutrients have been stored there for the future use of the plant.
Most root crops have larger amounts of carbohydrates and less protein and oil than grains (cereals) or legumes. Because of their bulk, root crops cost more to ship than do grains and most other food crops.
Therefore, root vegetables tend to be consumed locally. Nevertheless, measured in tons, root crops are comparable to grain crops on a worldwide basis. The most important root crops are the Irish (white) potato, the sweet potato, and cassava.
These three are to root crops what maize, wheat, and rice are to grain crops. They, together with root crops of secondary importance, are discussed below. The common name of each crop plant is followed by its scientific name and family name.
White Potato, The common potato, Solanum tuberosum (family Solanaceae), is the most important non grain food item of the world.However, it has been known outside the Americas for only a few centuries.
Spanish explorers of the sixteenth century found potatoes growing in what is now the nation of Colombia in South America. It had long been grown by Native Americans in the cool, high elevations of the Andes Mountains south to the present country of Chile.
Soon after discovery by Europeans, the potato was introduced into Spain and from there into other parts of Europe, including the British Isles. Throughout many of these regions, it became an important staple in the diets of most citizens.
When a fungal disease, potato late blight,wiped out most of the potato crop in Ireland in the mid 1840’s, a severe famine (the Irish Potato Famine) resulted, causing large numbers of people to emigrate to the United States, Canada, and other countries.
As a result, the popularity and cultivation of potatoes spread in North America, and the potato became known as the Irish potato, to distinguish it from the sweet potato. The potato is a crop of cool regions. Potato plants are grown from sections of the tuber cut into segments, each containing an “eye” (bud).
The resulting plants produce tubers that are harvested, usually by digging machines, later the same growing season. Principal potato-growing regions of the United States include Idaho, Maine, and New York. Many potatoes are also grown in northern Europe.
The potato is an economical source of starch used for both food and industrial purposes. Protein content is only about 2 percent. Purchases of whole potatoes declined throughout the later decades of the twentieth century, but that decline was offset by the increased consumption of processed potato products such as potato chips, ready-mix mashed potatoes, and frozen french fries.
Manihot esculenta (Euphorbiaceae), also called manioc and tapioca, is an important root crop and a staple item in the diets of more than 500 million people of tropical regions. The starch storage roots
are produced by the perennial plant, which is native to tropical America.
It is believed to have been domesticated in Brazil, where it is known to have been grown around 2000 b.c.e. In addition to Latin America, it is important in Africa and other tropical regions.
There are several advantages to growing and using cassava as a food plant. After clearing the land, farmers can plant stem sections. Storage roots can be harvested in only eighteen months or can be left in the ground and dug up later.
In addition to providing high yields per acre, cassava has the advantage of being resistant to diseases. Furthermore, it survives in poor soil and both dry and wet tropical climates.
One of the disadvantages of cassava is its low protein and vitamin content. Thus, an over dependence on cassava often results in severe nutritional deficiencies.
Also, the roots often contain poisonous cyanide-type compounds that must be removed before consumption. As the amounts of these compounds vary with the variety of cassava and the conditions under which they are grown, processes for removal of the toxins can be problematic.
Traditionally, in Brazil, the shredded roots are ground by and, after which the pulp’s mass is dried over fires to yield a subsistence product known as farinha. Also, a large, round flat bread is made by spreading the pulp on a griddle. In Africa, roots are produced from“sweet” varieties (in which only small quantities of toxins are present).
There, the roots are peeled, boiled, dried, and eaten as a lumpy, starchy vegetable with little flavor. In temperate regions, a product called tapioca, made from processed roots, is used for puddings.
Ipomoea batatas (Convolvulaceae), or the sweet potato, a relative of the morning glory, is a trailing tropical vine.Unlike those of the cassava, the edible parts of the sweet potato are true roots.
Evidence indicates that it is a native of South America, but it is known to have been cultivated more than a thousand years ago in Polynesia. It was also known in New Zealand before Europeans had ships that could cross the oceans. How the sweet potato was carried across the Pacific remains a mystery.
The sweet potato is cultivated today around the world, in the tropics as a perennial, and in temperate regions as an annual. In the latter case, the stem sections of the vine are planted in the spring, and the roots are dug up later the same season.
Sweet potatoes contain much more protein than either white potatoes or cassava; also, they have significant amounts of vitamin A. However, sweet potatoes do not store as well as cassava and are not grown in as high a quantity.
In the United States, they are prepared much like white potatoes. Large amounts are also fed to animals or used as sources of industrial products. China is the leading producer of sweet potatoes.
Other Root Crops
Perhaps the most important world root crop, after those listed above, is the yam, Dioscorea alata (family Dioscoreaceae). Not to be confused with sweet potatoes, which are often called “yams” in the southern United States, the true yamis, like the white potato, a tuber.
Also like potatoes, yams are propagated using sections of tubers with the buds. The resulting plants are deep-rooted climbing vines. One problem in harvesting them is the large amount of labor required to dig the tubers.
However, yams are well adapted to tropical rain forests. Yams are prepared as are white potatoes and have a similar nutritional value. In addition to Dioscorea alata, native to China, several other Dioscorea species are cultivated as root crops.
Several plants of the arum family, Araceae, are grown as root crops. The most important is taro, Colocasia esculenta. Taro is believed to have originated in southern Asia; it spread from there to India and also through the islands of the South Pacific. Later it was introduced into the Mediterranean, tropical Africa, and the West Indies.
The plant is closely related to “elephant ear,” which is grown as an ornamental. The edible portions include both tubers and corms. Visitors to Hawaii are familiar with the viscous preparation poi, which made from taro.
Onions and their close relatives of the genus Allium (family Liliaceae) have a long and esteemed reputation in the culinary arts. Native to Central Asia and the Near East, they have long been cultivated.
The bulbs, after being dug, can be consumed directly or stored. Onions (A. cepa) produce a single large bulb; garlic (A. sativum), several smaller ones. The bulb of the leek (A. ampeloprasum) is continuous with the leaf blade above.
Stem and Leaf Crops
Cole crops include cabbage and its close relatives, all of the species Brassica oleracea (family Brassicaceae), along with other plants of this family. There is evidence that from cabbage, native to northern Europe, each of the cole vegetables has resulted from a different modification of the stems or leaves.
Cabbage has long been an important crop in Germany, where it is used to make sauerkraut. Other vegetables of this group include brussels sprouts, cauliflower, kohlrabi, broccoli, and kale.
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It has been grown for centuries and used for salads, much as it is today. Selection has resulted in numerous varieties including leaf lettuce and romaine lettuce.
In the United States, iceberg lettuce is the familiar, popular type seen in supermarkets. Plants known as endive and chicory are also used as salads. Both are cultivars of Cichorium intybus.
Several other common vegetables, of various families, are grown for their edible stems or leaves. The principal edible parts of celery, Apium graveolens (familyApiaceae), are the stalks or leaf petioles.
Spinach, Spinacia oleracea (family Chenopodiaceae), is used raw in salads and as a cooked vegetable. Asparagus, Asparagus officinalis (family Liliaceae) isa perennial from which young shoots are cut each spring.