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Yam (vegetable)

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Yams are starchy, edible tubers produced by plants in the genus *Dioscorea*.

കാച്ചിൽ-കിഴങ്ങ്
കാച്ചിൽ-കിഴങ്ങ്

These plants belong to the Dioscoreaceae family and are monocots, making them relatives of grasses and lilies. Most yams grow as vigorous, perennial herbaceous vines. While there are approximately 870 known species, only a few are widely cultivated for food. Other species, such as *Dioscorea communis*, are toxic and cannot be eaten. The tubers themselves vary greatly in appearance due to many different cultivars. They often feature a rough, difficult-to-peel skin that ranges from light pink to dark brown. Once cooked, the inner flesh softens and can appear white, yellow, purple, or pink.

YamsatBrixtonMarket
YamsatBrixtonMarket

Cultivating yams requires specific environmental conditions and significant physical labor. The process begins at the start of the rainy season. Farmers plant whole seed tubers or tuber portions into mounds or ridges. The success of the yield depends on several factors. These include the size of the mounds and the spacing between plants. Farmers must also provide stakes for the climbing vines to grow upon. Because seed yams are bulky and perishable, farmers often save up to 30% of their harvest for next year's planting. Most yams require a humid tropical environment. They need annual rainfall that is distributed uniformly throughout the growing season. The plants follow a seasonal cycle where growth occurs in the wet season and dormancy occurs in the dry season.

Different species of yams have been domesticated independently across three continents. In Africa, humans domesticated *Dioscorea rotundata*. In Asia, the species *Dioscorea alata* was domesticated. In South America, people cultivated *Dioscorea trifida*. This long history of cultivation has spread yams to many temperate and tropical regions. The name "yam" likely derives from the Portuguese word *inhame* or Spanish *ñame*. These terms originated from Fula, a West African language used during trade. Interestingly, in Portuguese, the name often refers to the taro plant rather than *Dioscorea*. In many regions, the term "yam" is applied to unrelated vegetables. For example, many people in the United States call sweet potatoes "yams." In New Zealand, the oca is often called a yam, while in Malaysia, the name refers to taro.

In West Africa, the most economically important species are the yellow yam (*Dioscorea cayennensis*) and the white yam (*Dioscorea cayennensis subsp. rotundata*).

Yam at monday market kaduna state 01
Yam at monday market kaduna state 01

There are over 200 varieties of these yams. The white yam has a cylindrical shape and firm white flesh. The yellow yam contains carotenoids, which give the flesh its yellow color. The yellow yam also has a longer vegetation period and a shorter dormancy period than the white yam. These plants are large, with vines that can reach 10 meters in length. The tubers often weigh about 1 kilogram, though some can reach 5 kilograms. In Africa, these are frequently pounded into a paste to create a traditional dish called Iyan.

Ashanti Yam Ceremony 1817
Ashanti Yam Ceremony 1817

*Dioscorea alata*, known as the purple yam or water yam, has the largest global distribution of any cultivated yam.

Yam with numerous protruding fibers
Yam with numerous protruding fibers

It was first cultivated in Southeast Asia. It is grown across Asia, the Pacific islands, Africa, and the West Indies. This species was vital to seafaring Austronesian cultures. They carried these plants as "canoe plants" during migrations from Island Southeast Asia to Polynesia and Madagascar. The flesh of the *D. alata* tuber is typically white and has a watery texture.

Kaachil cut
Kaachil cut

Another important variety is the Chinese yam, *Dioscorea polystachya*. Native to China, this plant is more tolerant of frost and grows in cooler conditions. It is cultivated in Korea and Japan as well. Some varieties are used in traditional medicines or to make noodles.

Some species of the genus offer unique growth habits or challenges. The air potato, *Dioscorea bulbifera*, produces edible bulbils at the base of its leaves.

Starr 030807-0054 Dioscorea bulbifera
Starr 030807-0054 Dioscorea bulbifera

These bulbils are about the size of potatoes. While they can be eaten, some varieties require boiling or soaking to remove toxins. In Florida, the air potato has become an invasive species. It grows rapidly and crowds out native plants. It is difficult to remove because it can regrow from tubers or bulbils even after being burned. Another species, *Dioscorea dumetorum*, is known as the bitter yam. It is popular in West Africa because it requires less labor to grow. However, wild forms are highly toxic and have been used for criminal purposes or to poison animals.

Harvesting yams is a demanding task that requires great care.

In West Africa, farmers typically use sticks, spades, or diggers by hand. They often prefer wooden tools over metal tools. This is because metal is more likely to damage the fragile tubers. The work is physically taxing, requiring farmers to stand, bend, squat, or sit for long periods. The depth of the tuber in the soil affects how much effort is needed. Despite the high costs and labor, consumer demand remains very high. In many subregions of Africa, yam cultivation is a highly profitable venture for farmers.

yams production, World, 2023 (cropped)
yams production, World, 2023 (cropped)
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🖼️ Images & Media (16)
File:Yam at monday market kaduna state 01.jpg
Yam at monday market kaduna state 01.jpg
File:YamsatBrixtonMarket.jpg
YamsatBrixtonMarket.jpg
File:കാച്ചിൽ-കിഴങ്ങ്.JPG
കാച്ചിൽ-കിഴങ്ങ്.JPG
File:Kaachil cut.jpg
Kaachil cut.jpg
File:Yam with numerous protruding fibers.jpg
Yam with numerous protruding fibers.jpg
File:Dioscorea polystachya (batatas).jpg
Dioscorea polystachya (batatas).jpg
File:Starr 030807-0054 Dioscorea bulbifera.jpg
Starr 030807-0054 Dioscorea bulbifera.jpg
File:MS 1960.JPG
MS 1960.JPG
File:Dioscorea Bild1162.jpg
Dioscorea Bild1162.jpg
File:Tile on street depicting Aboriginal women gathering yams. Cooktown, Australia. 2005.jpg
Tile on street depicting Aboriginal women...
File:yams production, World, 2023 (cropped).svg
yams production, World, 2023 (cropped).svg
File:Igname frite2.jpg
Igname frite2.jpg

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