The Jerusalem artichoke (Helianthus tuberosus), also called sunroot, sunchoke, wild sunflower, topinambur, or earth apple, is a species of sunflower native to central North America. It is cultivated widely across the temperate zone for its tuber, which is used as a root vegetable.
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 lower part of the stem but alternate towards the top. 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 (2–4 in) in diameter, with 10–20 ray florets and 60 or more small disc florets. The flowers are briefly fragrant, giving off a light, vanilla-chocolate perfume.
The tubers are often elongated and uneven, typically 7.5–10 cm (3–3+7⁄8 in) long and 3–5 cm (1–2 in) thick, and vaguely resembling a ginger root in appearance, with a crisp and crunchy texture when raw. They vary in color from pale brown to white, red, or purple.
Before the arrival of Europeans, indigenous peoples cultivated H. tuberosus as a food source. The tubers persist for years after being planted, so the species expanded its range from central North America to the eastern and western regions. Early European colonists learned of this and sent tubers back to Europe, where they became a popular crop and naturalized there. It later gradually fell into obscurity in North America, but attempts to market it commercially were successful in the late 1900s and early 2000s.
The tuber 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: since inulin is not assimilated in the intestine, it does not cause a glycemic spike as potatoes would. Temperature variances have been shown to affect the amount of inulin the Jerusalem artichoke can produce. It makes less inulin in a colder region than when it is in a warmer region.
Originating in North America, the Jerusalem artichoke can now be found in several countries in North and South America, Europe, Asia, and Australia. In Central Europe it is one of the most expanding invasive plant species. It can grow in many geo-climatic regions and different types of soils. However, Jerusalem artichoke prefers moist habitats and seems to be less tolerant of dry conditions.
Because of its ecological and biological attributes, the Jerusalem artichoke is highly competitive with other plant species. For instance, the carbohydrates in the tubers serve as an energy source for rapid growth in spring. The plant expands rapidly and creates shading, which has a suppressing effect on neighbouring plants. Therefore, the risk of outcompeting and repressing the growth of native plants is increased.
