Culture
Winter hardy to USDA Zones 6 to 9 (some say Zone 5 with protection) where it is best grown in humus-rich, moist but well-drained soils in part shade, dappled shade, or almost full shade. Needs consistent moisture. Does poorly in heavy clay soils. Mulch in winter to protect plants from winter cold and late spring frosts. Plant tubers about 3-4" deep. May be grown from seed, but may take 3-5 years before plant will flower. In the St. Louis area, it should be planted in a sheltered location. Plants may spread rhizomatously to form colonies.
Noteworthy Characteristics
Arisaema ternatiartitum, commonly known as cobra lily or Jack-in-the-pulpit, is a tuberous woodland understory perennial that typically grows to 6-8” tall, but infrequently to as much as 18” tall. It is native to certain forested areas in Japan. Each plant produces two basal leaves, both of which are divided into three leaflets. A single flower structure emerges from the pseudostem in spring (April-May), each flower consisting of a showy, chocolate-purple-mushroom-brown, pitcher-like, hooded tube (spathe) which subtends and encloses a cylindrical, pencil-shaped flower spike (spadix). Tiny male or female flowers are located along the lower part of the spadix which rises slightly above the lip of the spathe in the shade of the arching and pointed spathe hood. Tiny female flowers are pollinated by insects, with the spathe and covering hood acting as a kettle trap. Plants go dormant in summer after flowering, except pollinated female flowers produce a vertical cluster of showy berries which ripen to bright red by late summer and become easily visible as soon as the spathe withers.
Plant parts contain calcium oxalate (same chemical as in diffenbachia or dumb cane) and are poisonous.
Genus name comes from Greek words aris meaning "arum" and aima meaning "red", in reference to the red-blotched leaves found on some species.
Specific epithet comes from the Latin words ternatus meaning in clusters of 3 and partitus meaning parted in reference to the plant leaves.
Problems
No serious insect or disease problems.
Uses
This plant may be difficult to locate in commerce. It should be planted in groups for ornamental interest and to insure pollination of female plants will occur with subsequent production of showy red berries. Best left undisturbed in shady woodland gardens, wild gardens or native plant areas.