Arisaema triphyllum

Did You Know?

• The plant is hardy to USDA plant hardiness zone 3.
• Arisaema triphyllum is imperiled at best (S1S2) in Manitoba.
• The plant contains calcium oxalate crystals as raphides in all parts, causing a powerful burning sensation if consumed raw.

Description

The Arisaema triphyllum complex includes four closely related species: Arisaema pusillum, Arisaema stewardsonii, Arisaema quinatum, and Arisaema triphyllum sensu stricto. A fifth species, Arisaema acuminatum, is sometimes included but its validity is controversial. The plant is a herbaceous perennial growing from a corm, typically reaching up to 2 feet tall, though populations in Georgia and Florida can grow almost twice that height. It bears one or two leaves, each divided into three leaflets, though lateral leaflets may occasionally be two-parted or lobed, giving the appearance of five leaflets.

The small flowers are borne on a fleshy spike called a spadix, which is enclosed by a large bract called a spathe. The inflorescence can be male, bisexual, or female, and individuals change sex based on size: small plants produce mostly male flowers, while larger plants produce female flowers. This phenomenon, known as dichogamy, is rare among flowering plants. The unripe fruits are smooth, shiny green berries that ripen to bright red in late summer and early fall.

Each berry contains one to five seeds, which germinate the following spring; seedlings require three or more years before they mature enough to flower.

Taxonomy

Arisaema triphyllum sensu stricto was first described as Arum triphyllum by Carl Linnaeus in 1753. Heinrich Wilhelm Schott placed it in the genus Arisaema in 1832. In 1940, Merritt Lyndon Fernald argued that Linnaeus's type was actually Arisaema pusillum, destabilizing the nomenclature. A proposal to conserve the name was considered but rejected in 1993, leaving the name Arisaema triphyllum (L. Schott as official but inherently unstable. Donald Grunert Huttleston introduced three subspecies in 1949 and a fourth in 1981. As of March 2023, all five taxa are recognized, though some authorities accept subspecies, others varieties, and some multiple species. Flora of North America lumps all taxa into a single species. Within the genus, A. triphyllum is classified in section Pedatisecta and is most closely related to Asian species such as A. amurense, not to other American Arisaema species.

Ecology

Arisaema triphyllum sensu lato flowers from April to June, with Arisaema triphyllum sensu stricto flowering first. In sympatric regions, Arisaema stewardsonii and Arisaema pusillum begin flowering one to two and two to three weeks later, respectively. In the southeastern United States, Arisaema quinatum flowers later than A. pusillum or A. triphyllum s.s. The plant is pollinated by fungus gnats, which are attracted by smell and trapped inside the flower.

Male flowers have an exit hole allowing gnats to escape, but female flowers lack this hole, trapping and killing the pollinators. Other insects such as gall gnats and beetles also visit. The plant is not self-pollinating because male flowers mature and die before female flowers on the same plant are mature, promoting outcrossing. The species are reproductively isolated in the wild, though a population intermediate between Arisaema stewardsonii and Arisaema triphyllum s.s. occurs near Clyde, New York, with glaucous leaves and strongly fluted spathes, growing in dry sandy soil.

Chromosome counts of six plants from this population showed four diploid (28 chromosomes) and two triploid (42 chromosomes) individuals.

Uses

When cooked, the root can be eaten as a vegetable; the calcium oxalate crystals give it a peppery flavor. Sliced and dried, it can be eaten like potato chips or ground into flour. Native Americans used a root preparation to treat sore eyes, rheumatism, bronchitis, and snakebites, and to induce sterility. The Meskwaki people reportedly chopped the corm and mixed it with meat, leaving it for enemies to find; the oxalate taste was masked by the meat, and consumption caused pain and death. They also used a seed in a cup of stirred water to determine a patient's fate: if the seed circled four times clockwise, recovery was expected; fewer circles indicated death.