Common Name: arisaema
Type: Herbaceous perennial
Family: Araceae
Native Range: Japan
Zone: 5 to 9
Height: 1.00 to 2.00 feet
Spread: 1.00 to 2.00 feet
Bloom Time: April to May
Bloom Description: Purple and white
Sun: Part shade to full shade
Water: Medium to wet
Maintenance: Medium
Suggested Use: Rain Garden
Flower: Showy
Fruit: Showy
Tolerate: Heavy Shade, Wet Soil
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 5 (perhaps 6) to 8. In the St. Louis area, it should be planted in a sheltered location.
Noteworthy Characteristics
Arisaema thunbergii commonly called cobra lily, is a woodland perennial that is native to forest areas in Japan. It is closely related to the jack-in-the-pulpit (Arisaema triphyllum) that is native to eastern North America. It typically rises to 12-24" tall topped by a solitary horizontal leaf clad with 9-17 narrow lanceolate leaflets. A single flower emerges from the ground in spring (April-May) near the base of the leaf petiole. The flower consists of a pitcher-like spathe (white with purple-speckled stripes) with a pointed blade-like hood (dark purple to near black) that drapes forward over the top of the pitcher. Hooded spathe reportedly resembles the head of a cobra hence the common name. An inner cylindrical upright flower spike known as the spadix (white at the base changing to purple) has a long purple whip-like tail which emerges over the collar-like lip of the spathe and trails outward to as much as 24" long.
Plants go dormant in summer after flowering, except some plants will produce a cluster of berries in mid-summer which become visible as the spathe withers. Berries ripen to red. 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.
Subsp. urashima is very similar to the species except for being slightly smaller in height (to 20” tall), leaf typically contains 11-15 broad-lanceolate leaflets and the throat has minor differences. Subsp. urashima is in reference to legendary Japanese fisherman Urashima Taro.
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 honors Japanese naturalist Carl Peter Thunberg (1743-1828).
Problems
No serious insect or disease problems.
Uses
Plant in groups. Best left undisturbed in shady woodland gardens, wild gardens or native plant areas.