Jerusalem artichoke* (Helianthus tuberosus) of the Aster (Asteraceae) family is a large, tuber-producing perennial that was an important food source for Native Americans and early settlers. The genus name combines two Greek words for “sun” and “flower”. The specific epithet is from Latin and means “with tubers”. This species occurs throughout the eastern U.S., as well as in eastern Canada, with scattered, presumably introduced occurrences in the western U.S. In Arkansas, it occurs across the northern half of the state and in scattered southern counties. Its preferred habitat is partially to fully sunny sites with moist loamy soils, such as found in creek and river floodplains and roadside ditches. Other common names include Canada potato, sunchoke (a commercial name), and girasole (Italian for “sunflower”).
In late summer into fall, in addition to the plant’s fibrous roots, thicker roots radiate out from the underground portion of the stem. These thicker roots terminate with light tan to reddish, stubby to elongate tubers that may be mostly smooth or knobby. Tubers may be 4 inches long and 2 inches across. These thin-skinned tubers are white and potato-like inside. Tubers, encircled by well-spaced growth rings, have a main bud at their distal end along with scattered secondary buds, especially on knobby projections. With maturity of tubers in mid-fall, parent stalks and roots die. Plants can produce numerous tubers so that thick colonies can grow over several years.
Photo 1: Along with a main bud (whitish tips), tubers also have smaller secondary buds. Growth rings encircle tubers. Upper large tuber is 2¾ inches long, ¾ inch wide. Photo in early December.
Spring growth, directly from over-wintering tubers, begins with appearance of leaves attached to a main stem. Through the growing season, stout erect stems may reach 4 to 10 or more feet. Round stems with short, stiff, white pubescence (scabrous) are generally a medium green but may be purplish. Main stems, to ¾ inch in diameter, feel bristly. Long branches grow from upper leaf axils, while short branches may grow from lower leaf axils.
Photo 2: Parent plant having died, new plants grow from tubers in mid-March.
Photo 3: Plants in this colony are showing early upper branches. Plants in foreground have been browsed by deer.
Leaves are medium green on upper surface and lighter green on lower surface, with an underside that is smooth due to soft pubescence and a scabrous upper side due to stiff, short pubescence. Leaves, widest at their bases, gradually taper to a point (acuminate). Largest leaves, typically occurring in opposite pairs below the inflorescence, are elongate-triangular with a blade up to 10 inches long and five inches wide on a 4-inch petiole. These largest leaves–pairs may be 5 or more inches apart along the stem–have a truncated base and serrated margins. Petioles of larger leaves are partially winged. Petioles of opposite leaf pairs are narrowly connected around the stem. Smaller alternate leaves, higher in the inflorescence and on short branches, are lanceolate with entire margins and have petioles that tend to be winged their entire length. Smaller alternate leaves also occur on short branches that occur below the inflorescence.
Primary venation consists of three prominent veins, namely a central vein or midrib and a pair of lateral veins that branch off midrib near its base. The two lateral veins gently curve toward leaf margin and continue in jagged manner parallel and close to the margin. Tertiary veining is offset pinnate. Veins are weakly depressed above and strongly expressed below.
Inflorescences of Jerusalem artichoke, in late summer into fall, consist of composite flower heads at the ends of stems and branches. The first flower heads to reach anthesis on the main stem or floral branches are the terminal heads. By the time the terminal flower head of the main stem or a branch is in bloom, heads on floral branches are already close to bloom. Depending on habitat and colony density, a plant may produce from several to 15 or more heads over a month or more.
Photo 4: Flower head bud on this 7-foot tall plant terminates the main stem. Secondary stems, as can be seen growing from leaf axils, will quickly also produce flower heads.
Flower heads, varying from 2½ to 4 inches wide with a disk varying from 3/8 to 5/8 inch wide, consist of 12 to 20 infertile ray florets and 50 or more fertile bisexual disk florets. Ray florets have a strap-like, yellow, pleated ligule with a rounded tip. Yellow, ¼ inch long disk florets are tubular with five flared lobes. Stamens of disk florets have dark anthers, connate to each other and arranged in columnar fashion around the style. Styles have a long, split (bifurcated) stigma whose branches coil backwards. Florets are set on a convex receptacle supported by a rounded involucre comprising about 30 overlapping, lanceolate-triangular phyllaries in several series. Phyllaries, slightly darker than the peduncles, have short pubescence, similar to that of the peduncles. Lower portions of phyllaries are appressed while long tapering ascending tips are flared to reflexed. In cross-section, the flower head is round. Peduncles, subtended by small leafy bracts, have the same appearance as their supporting stem or branch, including short pubescence.
Photo 5: Long, mostly leafless floral stalks terminate with a single flower head. Scabrous stems and branches may be purplish. Photo in mid-September.
Photo 6: Styles of disk florets become exserted above the dark anthers. Stigmas divide and coil backwards.
Photo 7: Phyllaries in several series form the involucre. Wide lower portions of phyllaries are appressed while long tapering tips are flared to reflexed.
Fertilized disk florets produce ¼ inch long, flattened, grayish achenes (dry one-seeded indehiscent fruits) tipped with two small quickly-dropped bristles. The principal source of reproduction is vegetatively via the tubers.
Photo 8: In this early November photo, with flower heads drying, large leaves (upper and lower surface shown) are about to drop while leaves on small axillary stems remain green. Achenes shown in inset. (A potter wasp [Eumenes sp.] built an urn of mud for one of its offspring on underside of large leaf on right.)
For a garden or natural area with mesic soil, Jerusalem artichoke, with its tall large-leafed stems and showy flowers, would be striking. However, stems may need to be staked and chemical control may be needed to prevent aggressive spreading by tubers. Tubers, high in dietary fibers (inulin) and minerals, may be eaten raw or variously cooked.
In addition to Jerusalem artichoke, 15 other types of Helianthus (sunflowers) occur in Arkansas. Jerusalem artichoke has characteristics that may cause it to be incorrectly identified as one of three woodland sunflowers (Helianthus strumosus, Helianthus divaricatus and Helianthus hirsutus). Jerusalem artichoke, typically found in more moist sites, tends to be a stouter and larger plant with larger stem leaves that have longer petioles. Tubers, found on Jerusalem artichoke in fall and winter, do not occur on the three woodland sunflowers. For articles regarding the woodland sunflowers, see here and here.
- Jerusalem artichoke, a native of North America, was an important food for Native Americans and early colonists. It was introduced to Europe where it became widely used for human and livestock food. The “Jerusalem” moniker is believed to be a corruption of the Italian word for “sunflower” (girasole, pronounced “jeer-uh-so-lay”). Jerusalem artichoke is not a true artichoke (Cynara cardunculus var. scolymus), but its tubers are said to have an artichoke flavor.
Article and photographs by ANPS member Sid Vogelpohl