Spring 1999

[TEXT ARCHIVE WEB-PUBLISHED MARCH 2002.
ORIGINAL PRINT PUBLICATION DATE: SPRING 1999.]

Skunk Cabbage: Methusalehs of the plant world

By Patricia Armstrong

Here in Chicago Wilderness my annual Rite of Spring always includes a pilgrimage to a swamp, marsh, calcareous fen, or springly place to listen for chorus frogs and spring peepers and to look for the skunk cabbage (Symplocarpus foetidus). As early as mid-February, but usually in March, when there's still snow on the ground and temperatures are around freezing, this most unusual member of the tropical Arum family melts its way out of the frozen ground and begins its startling bloom cycle.

Wrapped in a purple-streaked, flame-shaped cowl, the spathe pokes out of the ground and opens its cloak a little to reveal the purple club-shaped spadix inside. Thirty or so flowers are crowded together on the spadix. Most Arum flowers are unisexual and heat up their flowers to produce strong odors, which are often putrid or skunky, to attract pollinators. Skunk cabbage, however, is bisexual and often blooms when temperatures are too cold for pollinators to fly, but the flowers still produce heat.

William J. Hess at the Morton Arboretum and Roger M. Knutson in Iowa have both studied the production of heat in skunk cabbages during their bloom time. They found that skunk cabbage flowers could be 36 to 63 degrees F higher than the ambient air temperature. The spadix could be at 74 degrees F when the air temperature was around freezing. This heat is produced by oxidizing stored starch in the thick rhizome. In fact, Knutson found as temperatures dropped from 63 to 45 degrees F the plants nearly doubled their oxygen consumption. The spongy spathe is excellent insulation around the spadix and its dark color also absorbs heat energy from the sun.

The skunky odor and rotten meat color of the spathe appear to lure carrion flies and other pollinators to the flowers. People have observed carrion flies, honey bees, other small flies, gnats and spiders crawling on the spadix or seeking shelter inside the spathe, but only when the air temperature is above freezing. In fact, Knutson reports that one species of spider, Pachygnatha brevis, seems to use the warm skunk cabbage flower for mating and hatching its young.

Skunk cabbage's Latin name comes from the Greek meaning "connected fruits" and "rotten smell." Other Aroids in the Midwest include Jack-in-the-pulpit, green dragon, golden club, and water arum.

A pointed, curled cone of leaves pokes up beside the flower but does not unfurl until flowering is finished. The bright green leaves are two to three feet high and make a beautiful backdrop for golden marsh marigolds and lacy cinnamon ferns that fill the area in May. The spathe rots away leaving the spadix to develop in the soil.

The fruit of skunk cabbage — black and about the size of a flattened tennis ball — ripens in fall. It is marked on the outside somewhat like a pineapple and occurs at ground level. It disintegrates or rots or is eaten by rodents from the top down releasing the hard, marble-like seeds one at a time. They are mottled purple-brown with yellow streaks just like the spathe. They lie on the ground near the parent plant. Some fall into the water and float away to a new spot, and some are eaten or carried away and buried by mice and squirrels.

Skunk cabbages enchant us with their mysterious ways and winter blooming. With their contractile roots, they hunker down in atavistic, dank and mucky places and live for hundreds of years. "Methuselahs of the plant world," they've been called. They have "the fascination of a particularly crafty and devious old man," wrote the early 20th-century naturalist Donald Culross Peattie in his Almanac for Moderns, "wrapped in a cape, and pottering about down in the leafless copses for some dubious purpose." In any case, spring can't come to the Chicago Wilderness until the skunk cabbages have bloomed.