It may have escaped your notice, but spring has begun. Skunk cabbages officially kicked off the vernal season two or three weeks ago. Spring is also under way for the 70 sandhill cranes that passed through Calumet Park a week ago. And it is under way for killdeer, redwings, and grackles. The juncos that spent the winter here have begun to sing as they prepare to return to their breeding grounds in the north woods.
Skunk cabbages are aroids, members of the Araceae, a mostly tropical family with some unusual habits. The flowering parts of aroids consist of a cowl, called a spathe, that shelters a generally long, slender, and very phallic spadix. Many small flowers grow on the spadix. The Sumatran Amorphophallus titanum has a spadix up to six feet tall. Like the skunk cabbage, it caters to insects with low tastes. To attract them, it emits an almost overpowering odor that has been described as a combination of burnt sugar and rotting fish. Some of the volatile chemicals released by various aroids have been analyzed and named. The names are descriptive: skatole, for example, or–my own favorite–cadaverine.
Best of Chicago voting is live now. Vote for your favorites »
This system of pollination has serious drawbacks. The gnats get no reward for pollinating the flowers. They are apparently lured into the flowers by scents and colors that remind them of the sort of fungi they prefer for egg-laying sites. Any gnat that completes an actual pollen transfer dies without offspring. The only gnats that successfully reproduce are those that stay away from jack-in-the-pulpits. In other words, jack-in-the-pulpit plants are exerting selection pressure on these essential fungus gnats, the effect of which is to reduce the number of gnats available for pollination. Many jack-in-the-pulpit flowers produce few seeds, and it could be that generations of murdered pollinators are coming back to haunt them.
The massive amounts of energy needed to fuel this unique creature are stored in a thick underground stem that may be a foot long and several inches thick. Hundreds of smaller roots grow down into the soil from the upper part of this underground stem. Each fall these smaller roots shorten in unison, pulling the plant down into the soil. The downward movement is about equal to the annual increase in the length of the underground stem, perhaps half an inch. It can keep growing forever and always stay underground. The skunk cabbage is a warm-blooded plant that moves.
