Culture
Best grown in humus-rich, moist but well-drained soils in part shade to full shade. Needs consistent moisture. Does poorly in heavy clay soils. Plant tubers about 3-4" deep. May be grown from seed, but may take 3-5 years before plant will flower. Winter hardy to USDA Zone 6. In the St. Louis area, it should be planted in a sheltered location. Plants of this species are considered to be paradioecious (separate male and female plants in which the active fertile flowers which emerge on the spadix each spring may be of a different sex from year to year depending primarily upon the health and vigor of the plant). Young plants or plants experiencing stresses or female plants in the year following flowering will usually produce only fertile male flowers whereas healthy plants that are several years old and not subject to stresses often produce only fertile female flowers. In any given year, the fertile spadix flowers will be either male or female but not both.
Noteworthy Characteristics
Arisaema kiushianum, commonly called cobra lily, is a woodland perennial that is native to Kyushu, Japan. It is closely related to the jack-in-the-pulpit (Arisaema triphyllum) that is native to eastern North America. Each tuber produces a solitary leaf clad with 7-13 leaflets rising to 12-15" tall. A single flower structure rising to 8" tall emerges from the ground in spring (April-May) near the base of the leaf petiole. Although this flower structure appears from a distance to be one large flower, it is in reality a complicated structure consisting of (a) a pitcher-like spathe with a blade-like hood that drapes forward over the pitcher opening and (b) a thin, upright, cylindrical flower spike known as the spadix which contains the very tiny male or female flowers that form on the lower part of the spadix. The spadix is encircled by the showy spathe but extends over the lip of the spathe and outward like a tail to about 5". The spathe is dark purple with white stripes and a noticeable white mark below the back inside lip. The spadix is dark purple. Plants go dormant in summer after flowering, except pollinated female plants will produce a vertical cluster of showy berries on the spadix. Berries ripen to bright red by mid- to late summer and are easily visible as soon as the spathe withers. Stalks, leaves, flowers and fruits give this plant a tropical aura. All 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.
Problems
No serious insect or disease problems.
Uses
Plant in groups for ornamental interest and to insure pollination of female plants. Best left undisturbed in shady woodland gardens, wild gardens or native plant areas.