Helianthus tuberosus L.

Jerusalem Artichoke

Helianthus tuberosus plant

Family - Asteraceae

Stems - Erect, sometimes somewhat sprawling late in season, up to 3 m tall, stout, sparsely to densely pubescent with bristly, whitish to silvery hairs.

Helianthus_tuberosus_stemStem with whitish bristly hairs.

Helianthus_tuberosus_stem2

Leaves - Usually opposite on lower stem, becoming alternate near inflorescence, well-developed along stem, with winged petioles. Blades to 25 cm, ovate, thick textured, flat, sharply pointed, toothed along margins, upper surface strongly roughened, lower surface densely pubescent, with 3 main veins, the lateral veins branching from the midvein well above the base.

Helianthus_tuberosus_leafLeaf (adaxial).

Helianthus_tuberosus_leaf2Leaf (abaxial).

Helianthus_tuberosus_leaf3Winged petiole.

Inflorescence - Solitary heads or, more commonly, open panicles, often with numerous heads.

Helianthus_tuberosus_inflorescenceInflorescence.

Involucres - Involucre 8-12 mm long, 10-25 mm in diameter, the bracts in 3 or 4 overlapping series, lanceolate, tapered to a sharply pointed tip, the margins with a fringe of short hairs, the outer surface glabrous or pubescent.

Helianthus_tuberosus_involucresInvolucres.

Heads - Up to 8 cm in diameter. 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, minutely hairy toward the tip.

Helianthus_tuberosus_headsHeads.

Florets - Ray florets 10-20, sterile, 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 perfect, numerous, the corollas 6-7 mm long, yellow. Pappus of 2 scales 2-3 mm long, these lanceolate to narrowly triangular, sharply pointed, often with a minute awnlike tip.

Helianthus_tuberosus_floretsDisk and ray florets.

Fruits - Achenes 5-7 mm long, wedge-shaped, somewhat flattened and more or less 4-angled in cross-section, the surface mostly glabrous, brown, sometimes purplish-tinged.

Flowering - August - October.

Habitat - Streambanks, forests, sloughs, pond margins, roadsides, pastures.

Origin - Native to the U.S.

Other info. - This showy, staturesque plant grows throughout Missouri and is a common sight along roadsides. It is a member of a complex of Helianthus species which can present significant challenges to identification. This one is relatively easy, having distinctive whitish, bristly hairs along a robust stem and large, ovate leaves with a winged petiole. The leaf arrangement usually moves from opposite to alternate high on the stem, and when this is seen in combination with the other characters it is nearly conclusive evidence for the species.

The plant produces fleshy, edible tubers known as "Jerusalem artichokes," though they are unrelated to artichokes and are not native to the Middle East. They were used as a food source by Native Americans, and more recently by peoples of both the Old and New Worlds. A hybrid between this species and H. annuus shows improved tuber production, and these have been marketed under the name "sunchokes." The tubers contain an unusual oligosaccharide (inulin) which tastes sweet but is not digested or absorbed in the human GI tract, and is therefore safe for diabetics.

A large attempt in the early 1980s to farm these plants for production of ethanolic biofuels resulted in a spectacular failure due to mismanagement and unfavorable politics. The investment losses and bad publicity resulted in loss of confidence in the agricultural potential of H. tuberosus, and cultivation has declined significantly since then.

Photographs taken along the Katy Trail, Warren County, MO, 9-22-2013; Tyson County Park, St. Louis County, MO, 8-28-2017; near Catawissa Conservation Area, Franklin County, MO, 9-11-2018; and at Shaw Nature Reserve, Franklin County, MO, 9-12-2018 (SRTurner).



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