The Jerusalem artichoke (Helianthus tuberosus), also called sunroot, sunchoke, earth apple, or topinambour, is a species of sunflower native to eastern North America, and found from eastern Canada and Maine west to North Dakota, and south to northern Florida and Texas. It is also cultivated widely across the temperate zone for its tuber, which is used as a root vegetable.

Scientific classification
Kingdom:    Plantae
Clade:    Angiosperms
Clade:    Eudicots
Clade:    Asterids
Order:    Asterales
Family:    Asteraceae
Genus:    Helianthus
Species:    H. tuberosus

Description
Helianthus tuberosus is a herbaceous perennial plant growing to 1.5–3 m (4 ft 11 in–9 ft 10 in) tall with opposite leaves on the upper part of the stem but alternate below. The leaves have a rough, hairy texture. Larger leaves on the lower stem are broad ovoid-acute and can be up to 30 cm (12 in) long. Leaves higher on the stem are smaller and narrower.

The flowers are yellow and produced in capitate flowerheads, which are 5–10 cm (2.0–3.9 in) in diameter, with 10–20 ray florets and 60 or more small disc florets.

The tubers are elongated and uneven, typically 7.5–10 cm (3.0–3.9 in) long and 3–5 cm (1.2–2.0 in) thick, and vaguely resembling ginger root in appearance, with a crisp texture when raw. They vary in colour from pale brown to white, red, or purple.

Food use
Before the arrival of Europeans, Native Americans cultivated H. tuberosus as a food source. The tubers persist for years after being planted, so that the species expanded its range from central North America to the eastern and western regions.[citation needed] Early European colonists learned of this, and sent tubers back to Europe, where it became a popular crop and naturalized there. It later gradually fell into obscurity in North America, but attempts to market it commercially have been successful in the late 1900s and early 2000s.

The artichoke contains about 2% protein, no oil, and little starch. It is rich in the carbohydrate inulin (8 to 13%), which is a polymer of the monosaccharide fructose. Tubers stored for any length of time convert their inulin into its component fructose. Jerusalem artichokes have an underlying sweet taste because of the fructose, which is about one and a half times as sweet as sucrose.

It has also been reported as a folk remedy for diabetes. Temperature variances have been shown to affect the amount of inulin the Jerusalem artichoke can produce. When not in tropical regions, it makes less inulin than when it is in a warmer region.

Etymology
Despite one of its names, the Jerusalem artichoke has no relationship to Jerusalem, and it is not a type of artichoke, though the two are distantly related as members of the daisy family. The origin of the "Jerusalem" part of the name is uncertain. Italian settlers in the United States called the plant girasole, the Italian word for sunflower, because of its familial relationship to the garden sunflower (both plants are members of the genus Helianthus). Over time, the name girasole (pronounced closer to [d͡ʒiraˈzu:l] in southern Italian dialects) may have been changed to Jerusalem. In other words, English speakers would have corrupted "girasole artichoke" (meaning, "sunflower artichoke") to Jerusalem artichoke. Another explanation for the name is that the Puritans, when they came to the New World, named the plant with regard to the "New Jerusalem" they believed they were creating in the wilderness. Also, various other names have been applied to the plant, such as the French or Canada potato, topinambour, and lambchoke. Sunchoke, a name by which it is still known today, was invented in the 1960s by Frieda Caplan, a produce wholesaler who was trying to revive the plant's appeal.

The artichoke part of the Jerusalem artichoke's name comes from the taste of its edible tuber. Samuel de Champlain, the French explorer, sent the first samples of the plant to France, noting its taste was similar to that of an artichoke.

The name topinambur, in one account, dates from 1615, when a member of the Brazilian coastal tribe called the Tupinambá visited the Vatican at the same time that a sample of the tuber from Canada was on display there, presented as a critical food source that helped French Canadian settlers survive the winter. The New World connection resulted in the name topinambur being applied to the tuber, the word now used in French, German, Italian, Romanian, Russian, and Spanish.

Cultivation and use
Unlike most tubers, but in common with many other members of the Asteraceae (including the artichoke), the tubers store their carbohydrate as inulin (not to be confused with insulin) rather than as starch. So, Jerusalem artichoke tubers are an important source of inulin used as a dietary fiber in food manufacturing.

Crop yields are high, typically 16–20 tonnes/ha for tubers, and 18–28 tonnes/ha green weight for foliage. Jerusalem artichoke also has potential for production of ethanol fuel, using inulin-adapted strains of yeast for fermentation.

Jerusalem artichokes are easy to cultivate, which tempts gardeners to simply leave them completely alone to grow. The quality of the edible tubers degrades, however, unless the plants are dug up and replanted in fertile soil. Because even a small piece of tuber will grow if left in the ground, the plant can ruin gardens by smothering or overshadowing nearby plants and can take over huge areas. Farmers growing Jerusalem artichokes who then rotate the crop may have to treat the field with a weedkiller (such as glyphosate) to stop their spread. Each root can make an additional 75 to 200 tubers during a year.

The tubers are sometimes used as a substitute for potatoes: they have a similar consistency, and in their raw form have a similar texture, but a sweeter, nuttier flavor; raw and sliced thinly, they are fit for a salad. Their inulin form of carbohydrates give the tubers a tendency to become soft and mushy if boiled, but they retain their texture better when steamed. The inulin cannot be broken down by the human digestive system but it is metabolized by bacteria in the colon. This can cause flatulence and, in some cases, gastric pain. Gerard's Herbal, printed in 1621, quotes the English botanist John Goodyer on Jerusalem artichokes:

which way soever they be dressed and eaten, they stir and cause a filthy loathsome stinking wind within the body, thereby causing the belly to be pained and tormented, and are a meat more fit for swine than men.

Jerusalem artichokes have 650 mg potassium per 1 cup (150g) serving. They are also high in iron, and contain 10-12% of the US RDA of fiber, niacin, thiamine, phosphorus, and copper.

Jerusalem artichokes can be used as animal feed, but they must be washed before being fed to most animals. Pigs can forage, however, and safely eat them directly from the ground. The stalks and leaves can be harvested and used for silage, though cutting the tops greatly reduces the harvest of the roots.
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