16. Helianthus tuberosus L. (Jerusalem artichoke)

H. tuberosus var. subcanescens A. Gray

Pl. 283 e, f; Map 1203

Plants perennial herbs, with slender, long-creeping, branched rhizomes (the branches usually with small tubers at the tip), usually occurring in dense colonies. Stems usually solitary, less commonly appearing in small clumps, 80–300 cm long, sparsely to more commonly moderately pubescent with short, stiff, loosely ascending, usually pustular-based hairs, not glaucous, sometimes nearly glabrous toward the base. Leaves well developed along the stem (usually with 8–20 nodes), mostly opposite (usually alternate in the upper third), with a short to less commonly long, sometimes poorly differentiated, partially winged petiole (the petioles of the larger leaves 1.5–8.0 cm long). Leaf blades 6–25 cm long, 3–15 cm wide, relatively usually moderately thick-textured, oblong-lanceolate to lanceolate or ovate (mostly 2–4 times as long as wide), flat, not folded longitudinally, short- to more commonly long-tapered at the base, tapered to a sharply pointed tip, the margins finely to coarsely toothed, flat, the upper surface strongly roughened with moderate to dense, minute, stout, pustular-based hairs, the undersurface moderately to densely pubescent with somewhat softer, loosely appressed to more or less spreading hairs, also with sparse to moderate, sessile, yellow glands, with 3 main veins, the lateral pair branching from the midnerve well above the base of the blade, arching upward. Inflorescences of solitary terminal heads or more commonly appearing as open clusters or open panicles. Involucre 8–12 mm long, 10–25 mm in diameter, about as long as or slightly longer than the tips of the disc corollas, the bracts in 3 or 4 subequal, overlapping series, narrowly lanceolate to lanceolate, often darkened or with a dark stripe toward the base, tapered to a sharply pointed, loosely ascending to spreading or recurved tip, the margins with an irregular fringe of short, spreading to ascending hairs, the outer surface glabrous or more commonly sparsely to moderately pubescent with short, stout or slender, ascending hairs, but usually lacking sessile, yellow glands. Receptacle convex to short-conical, the chaffy bracts 8–9 mm long, narrowly oblong to narrowly oblong-oblanceolate, usually with 3 short, sharply pointed lobes at the tip, these green or straw-colored, the outer surface minutely hairy, especially toward the tip. Ray florets 10–20, the corolla 2–4 cm long, the outer surface with sparse to moderate, minute hairs and usually also scattered, minute, sessile, yellow glands. Disc florets with the corolla 6–7 mm long, the corollas yellow, the lobes glabrous or with a few inconspicuous, minute hairs on the outer surface. Pappus of 2 scales 2–3 mm long, these lanceolate to narrowly triangular, tapered to a sharply pointed, often minutely awnlike tip, occasionally also with an additional minute, oblong scale 0.4–0.8 mm long. Fruits 5–7 mm long, wedge-shaped to narrowly obovate, somewhat flattened and more or less 4-angled in cross-section, the surface glabrous or with a few minute hairs at the tip, uniformly brown or with fine, darker and lighter brown mottling, sometimes purplish-tinged. 2n=102. August–October.

Scattered to common throughout the state (eastern U.S. west to North Dakota and Texas; Canada; introduced westward to the Pacific Coast). Banks of streams, rivers, and spring branches, bottomland forests, mesic upland forests, sloughs, margins of ponds and lakes, and moist depressions of upland prairies; also pastures, fencerows, railroads, roadsides, and disturbed areas.

Heiser et al. (1969) stated that this species is exceedingly variable morphologically, but that most plants are fairly easily recognized by the alternate upper leaves, leaf blades that are relatively coarsely toothed and longer-tapered at the base, and involucral bracts that often are darkened toward the base, among other features. They discussed, however, difficulties in separating some specimens from H. strumosus. Heiser and his colleagues treated var. subcanescens as part of the environmentally based variation in the species but noted that plants determined by Steyermark (1963) as this variety actually represented misdetermined specimens of H. strumosus. The origins of this hexaploid (2n=102) species are not fully understood, and the degree to which it hybridizes with other sunflower species in nature requires further study. For discussion of putative hybrids with H. rigidus (known as H. ×laetiflorus), see the treatment of that species.

The seasonally produced fleshy tubers produced by this species are edible and have a crisp texture and a flavor reminiscent of nuts and artichokes; they can be eaten raw, cooked, or pickled. They contain the storage-carbohydrate inulin (instead of starch), which is a fructose-based oligosaccharide with a slightly sweet flavor that passes through the human digestive tract largely undigested and is thus tolerated well by persons with diabetes. Inulins occur in a large number of plants (see also the treatment of Cichorium [Asteraceae tribe Cichorieae]) and are extracted commercially from a few species for use as a soluble fiber dietary supplement and as a bulking agent and fat substitute in some foods, especially some brands of yogurt.

Heiser (1976) reviewed the history of Jerusalem artichoke cultivation. Although there is no archaeological data to document the antiquity of the food use of this species in North America, the historical use of both cultivated and wild-collected plants by various tribes of Native Americans has been well documented (Moerman, 1998). The plant reached Europe in the early 1600s, where it was cultivated and became a fashionable food item for a time, but it was never economically of major importance. Russian plant breeders used H. tuberosus as a source of disease resistance in breeding programs to improve strains of the giant annual sunflower. An artificial hybrid between H. tuberosus and H. annuus also has been bred in the United States with improved tuber production, and it has become available commercially under the name sunchoke. Today, both Jerusalem artichokes and sunchokes are both available in various forms in some grocery stores, particularly health food stores, although not as commonly as they were during the 1980s.

Amato (1993) chronicled the remarkable account of the brief and unfortunate attempt to develop Jerusalem artichoke (which is neither native to the Middle East nor closely related to artichokes) as an alternative crop for ethanol production as a source of alternative energy. During a period of about 18 months beginning in 1981, a Minnesota company called American Energy Farming Systems convinced farmers from agriculturally depressed areas of 31 states and 3 Canadian provinces to invest more than 25 million dollars in Jerusalem artichoke seeds for this purpose. Through a combination of bad politics and financial mismanagement, this enterprise failed spectacularly, and the company owners subsequently were prosecuted as con artists. A regrettable consequence of this series of events was a loss of confidence in the overall crop potential of H. tuberosus and a sharp decline in its cultivation.