Intriguing Arisaemas By Gene Bush

Once mainly the province of collectors, these fascinating aroids—the most widely known of which is Jack in the pulpit—are now popular shade garden plants.
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Photo credits: Arisaema triphyllum by Gene E. Bush; A. triphyllum berries by David Cavagnaro.

Of all the plants I have grown over my many years as a gardener and nursery owner, arisaemas (Arisaema spp.) are undoubtedly the most fascinating. These mysterious and captivating plants look exotic but are hardy and easy to grow. I can’t imagine my shade garden without them.

When I first began collecting arisaemas some 15 years ago, only a couple of the 150 or so species in the genus were readily available. But, thanks to the efforts of plant fanatics such as Tony Avent of Plant Delights Nursery and Barry Yinger of Asiatica Nursery, dozens of exotic species are now relatively easy to obtain from popular garden catalogs. The Internet and specialty plant exchanges are providing further sources of previously hard-to-find selections.

If you haven’t already succumbed to the temptation to try arisaemas in your garden, there’s no time like the present. But I offer fair warning, once you’ve started, it’s hard to stop at just one or two!

Background and Botany

Arisaemas are the third largest genus—after anthuriums and philodendrons—in the arum family (Araceae). The center of diversity for arisaemas is in Asia—particularly the Himalayan region, China, and Japan—but they also range into the Middle East, Africa, and North America. They are primarily found in seasonally moist, woodland habitats, and most are native to temperate zones, which makes them adaptable to a wide range of gardens in the United States.

Arisaemas are herbaceous plants that grow from—depending on species—tubers or rhizomes. Despite what you might assume after seeing them in “bloom,” arisaemas are really mostly about foliage. In addition to one to three “true” leaves that develop on each plant, what is generally thought of as the flower is actually a modified leaf that curls into a tube, broadening at the tip to form a hood (spathe).
Inside this tube, the inconspicuous true flowers form on a slender club called a spadix. In some species, a band of male flowers forms near the top of the spadix, followed by a sterile band and then a band of female flowers. If pollen from the male flowers reaches the female flowers—and sufficient energy is available in the tuber—seeds will form inside fleshy berries. Most plants are pollinated by flies and beetles.

Berries are produced in tight clusters, usually turning a brilliant waxy red by fall. Because I grow a number of species with different blooming and fruiting sequences, I enjoy a flowering season from March through July, followed by a colorful berry display from September to early December.

When it comes to reproduction, some arisaemas behave in rather unusual ways. Plants can be monoecious as described above, having both male and female flowers at maturity. Some species are dioecious—the male and female flowers are on separate plants. And some change their gender from one year to another in response to environmental conditions.

Growing Arisaemas

Much of the published information about winter hardiness of arisaemas is outdated. USDA Hardiness Zones of 6 to 8 are still quoted for many Asian species, although many have survived in my southern Indiana nursery and garden when temperatures dropped below –30 degrees Fahrenheit, and without benefit of snow cover.

Before selecting an arisaema for your garden, determine whether it emerges early, mid-season, or late. Species break dormancy at varying times in spring, and although a species may be hardy, if it begins growth too early, it can be injured by a late freeze. In southern Indiana, we often get a warm spell during February that lasts seven to 10 days, then it’s back to winter. Arisaemas that emerge during those mild days are often damaged.

The best time to plant new arisaemas is in late summer or early fall, so the tubers have time to set roots before the plant goes dormant for winter. Plant tubers four to six inches deep in free-draining organic soil as described below.

I treat all the species I grow pretty much the same. My garden is on the north side of a hill, shaded by trees and shrubs. The original clayey soil has been steadily amended with organic matter so that it’s now moist yet well-drained.

Arisaemas respond well to an annual light dressing of composted manure or a balanced fertilizer. Each fall, I mulch with chopped leaves that break down to provide additional nutrients and organic matter.

North American Species

Three arisaema species are found in North America, but one (A. macrospathum) is endemic to the highlands of central Mexico and is not hardy enough for me to cover here.

The arisaema most familiar to American gardeners is Jack in the pulpit (A. triphyllum, USDA Hardiness Zones 4–9, AHS Heat Zones 9–1). Native to moist woodlands in most states east of the Rocky Mountains, Jack was the first arisaema in my collection. Its common name stems from the fancied resemblance of its inflorescence to a preacher (the spadix) standing in a covered pulpit (the spathe).
Not surprisingly, given its wide native range, Jack in the pulpit is quite variable in appearance, and botanists recognize several subspecies. You can find local populations that have green stems and inflorescences, dark or spotted stems and dark chocolate blooms, or any combination between the two. Mature plants vary considerably in size—some grow almost four feet tall, others never exceed 18 inches.

Jack is very adaptable and can live well over 25 years in suitable environments. Following an especially favorable year, its tuber can increase 200 percent in size.
Normally, a mature Jack has two leaf stems (petioles) that arise from the main stalk (psuedostem) that emerges from a tuber. Each leaf has three leaflets except for a subspecies, A. triphyllum subsp. quinatum, which has five leaflets. The inflorescence arises on a stem (peduncle) of its own between the two leaves. The plant emerges in late April in my garden, and I enjoy watching it literally unfurling like an umbrella.

Green dragon (A. dracontium, Zones 4–9, 9–6) shares much the same range as Jack in the eastern United States, but is considered endangered or threatened in some areas of New England. It is often found growing in moist drainage ditches or swampy areas where it typically reaches two to three feet tall.

Green dragon will grow happily in normal garden soil, but without extra moisture tends to max out at about two feet. The long stalked leaf is shaped like an open half circle at the end of a stick. Around the outside of that circle are five to 15 individual leaflets.

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