What is Arisaema?

Helga George

Arisaema is a genus of flowering plants in the arum family, Araceae. Many species are found in Asia and Africa, and are known as cobra lilies. A common species in North America is Arisaema triphyllum, or the Jack in the Pulpit plant. This arum is found in wet places, such as bogs, and grows well in shade. The whole plant is poisonous, but one should be particularly wary of the red fruits produced in the fall.

Man mowing the grass
Man mowing the grass

Jack in the Pulpit plants are perennials native to eastern North America. They have a wide range, growing from Canada to Florida and west to Minnesota, in thickets and woodlands. The plants are grown in Europe mainly as horticultural specimens.

All of the Arisaema species grow from specialized bulbs known as corms. Jack in the Pulpit corms planted in the fall should produce foliage the following spring, if planted in soil that is wet. The leaves grow in groups of three and resemble those of poison ivy.

The plant derives its common name from the flowers, which can vary greatly in color and appearance. They all have a spathe that is called a pulpit, which twists around to cover the spadix, known as jack. On the spadix are a number of small flowers. The plants change their sex as they grow older. They start out with mostly male flowers, while larger, older plants produce mostly female flowers.

The flowers are pollinated by flies, which is common for arums. The blooms use heat to generate a rancid odor to attract the insects. Once pollinated, shiny green fruit are produced on the spadix. The fruit turn red in the fall, with each one generally containing one to five seeds.

These plants contain calcium oxalate, which makes them poisonous. They are rarely eaten by deer. Jack in the Pulpit is one of the few specimens that can grow under black walnut trees. This is notable because these trees produce a compound that is toxic to most other plants.

Some gardeners grow these plants in specially-constructed rain gardens. Such gardens are usually built in an area where rain naturally flows downhill. Poorly drained areas are avoided.

Arisaema tortuosum, or the whipcord cobra lily, is another Arisaema species of horticultural interest. It can grow to 7 ft (2.1 m) tall. It presents a striking appearance with its spadix. First, the organ grows horizontally and then suddenly turns vertically. The appearance of the spadix has been compared to a whip, and has given rise to its common name. The whipcord cobra lily is native to Asia.

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