Skunk Cabbage (Symplocarpus foetidus)

People often find it strange that I’ve spent parts of six years studying skunk cabbage and that I’m an unabashed admirer of this plant. After all, skunk cabbage stinks and has no beautiful blossoms. But I’m not alone. A friend of mine was driving along the northern California coast and, being attuned to skunk cabbage through my influence, she noticed a well-fashioned wooden sign on the roadside she may have overlooked otherwise: “Skunk Cabbage Discovery Trail.”

The unknown comrade who made that trail has probably shared my experience that there’s much more to skunk cabbage than meets the casual eye. In this essay I can’t take you on such a trail—you’d have to come to our wetland boardwalk for that—but I can share with you some of the discoveries I’ve made on my journeys to skunk cabbage over the past years.

The Flowering Bud

To find the first spring plant in flower in our region—the edge of the Taconic range an hour southeast of Albany, New York—you have to get out before it feels much like spring at all. It’s March, the ground is still frozen, and frost comes nearly every night. The days are rapidly getting longer, but the spring equinox is still ahead. Walking through the woods, you see the grey and brown tree trunks, a coloring mirrored in the ground litter of leaves from the previous year. There is no green. Not only the temperature but the whole mood of the woods is cool.

Then you walk down to the edge of a meandering stream or, in my case, to a wooded wetland. Here, too, the ground is frozen, and patches of ice spread between groups of bushes and small trees (mainly red maples and alders) that dominate the wetland. In this still, quiescent world, little centers of emerging life are visible, the first sign of early spring. What I see are the four-to-six-inch-high, hood-like leaves that enclose the flowers of skunk cabbage.

Both color and shape are striking. Some leaves are completely deep wine-red or maroon, while in others this background coloring is mottled with patches or stripes of yellow or yellow green. The shape is hard to describe: it’s like a spiral, sculpted hood drawn around itself, leaving only a narrow opening on one side. I’ve often thought that if an artist were searching for an appropriate image of a gnome or dwarf, she would find it in these little figures emerging from the ground when everything else is still in a wintry sleep. Not only the colors, but also the specific shapes are manifold; some are pointed and strongly twisted, others rounder and squat. As my eye sweeps over the twenty or thirty plants before me, my gaze is brought into a spiraling movement when it tries to rest upon any single specimen. The deep color is warm, the sculpted form alive.

Looking at skunk cabbage on one of the first warm, sunny March afternoons (it’s maybe 50° F) with the light shining through the leafless trees and shrubs and illuminating the wetland floor, I often sense for the first time that spring is on its way. On such days I’ve even seen the first bees of the year flying in and out of the skunk cabbage hoods.

The hood is, in botanical terms, a highly modified leaf called a spathe. The spathe wraps around itself to form a space that encloses a spherical head of flowers, called a spadix (figure 2). The spathe functions as a bud that holds and protects the flower when it emerges out of the ground. But it is a bud that never unfolds. When the flowers are full in bloom, they are still enwrapped by the spathe. You can see the flower head only by peeking inside the narrow opening in the spathe.

The roundish flower head (about 2 cm in diameter) has a spongy consistency like the spathe itself. It consists of numerous small, tightly packed individual flowers (figure 3). They have no petals, which make up the showy part of the flower in most plants. Rather, they have four inconspicuous, fleshy, straw-colored sepals (which in many plants form the bud leaves enclosing the petals) that never really unfold.

The flowers “bloom” when the stamens grow up between and above the sepals and release their pale yellow pollen. Following this the style grows out of the middle of each flower to be pollinated by insects carrying pollen from other flower heads. All of this happens within the enclosing spathe. These first flowers of spring never leave their protective enclosure.

A couple of times I’ve been lucky enough to see spathes growing up through a thin layer of ice, the ice melted around the spathe in a circular form. This is an indication of skunk cabbage’s remarkable capacity to produce heat when flowering. If you catch the right time, you can put your finger into the cavity formed by the spathe and when you touch the flower head, your finger tip warms up noticeably. Biologist Roger Knutson found that skunk cabbage flowers produce warmth over a period of 12-14 days, remaining on average 20° C (36° F) above the outside air temperature, whether during the day or night. During this time they regulate their warmth, as a warm-blooded animal might!

Physiologically the warmth is created by the flower heads breaking down substances while using a good deal of oxygen. The rootstock and roots store large amounts of starch and are the likely source of nutrients for this break down. The more warmth produced, the more substances and oxygen consumed. Knutson found that the amount of oxygen consumed is similar to that of a small mammal of comparable size.

We must imagine that as the spathe grows out of the usually frozen ground, the flower head heats up and the warmth radiates outward. While in this heating phase, the flowers bloom, releasing pollen and being pollinated by insects. Not only can you see the first insects flying around between skunk cabbages, but you also find beetles and spiders crawling around within the warm enclosures of the spathes. You can even discover a spathe opening veiled with a spider net.

The flowers also release a noticeable odor at this time. On a calm day coming down to the wetland you can smell a lightly pungent, somewhat skunk-like odor. If you put your nose to the opening of a spathe, the scent is markedly stronger. Small flies and other insects are attracted to the flowers by the smell. These creatures are in part the same species that are attracted to carrion—decomposing flesh. Some of the typical volatile organic compounds released by a decomposing carcass—with graphic names like putrescine and cadavarine—are also formed by the flowers of some members of the Arum family (Araceae), to which skunk cabbage belongs. Whether skunk cabbages emit precisely these or other related compounds has not yet been investigated.

Due to the warmth production, a constant circulation of air in and out of the spathe occurs. From the flower head, warmth is generated and the air moves up and outward, while cooler air is drawn into the spathe. A vortex is formed with air streaming along the sculpted, curved surfaces of the spathe. In a habitat with numerous skunk cabbages, a microcosm of flowing warmth and odiferous air is created in which the first insects of spring fly.

This is the world of skunk cabbage over a number of weeks in March and sometimes into April: on the one hand, the enclosed, protected life just peering out of the still wintry earth, and a flower that remains in a bud; on the other hand, the active, warmth-, movement-, and scent-emanating organism that creates a unique environment for the first stirrings of insect life. Skunk cabbage mirrors the quality of early spring—flowering at ground level in a bud that doesn’t open, while at the same time helping to create the environment for its own development.

Rapid Unfolding and Decay

When the spathe emerges out of the ground, there is often the tip of a large bud next to it, sticking an inch or two out of the ground (figure 4). This bud contains all the leaves that will develop on the plant and is often already visible in the fall. Only when the spathe slowly begins to wilt does this tightly-packed bud of leaves begin to grow. It grows longer than the spathe and is shaped like the tip of a spear. Then, when the days begin to get noticeably warmer at the end of April and into May, the bud unfolds rapidly. It’s clear that skunk cabbage now needs outer warmth to develop. The bright green leaves unfold in a beautiful spiraling pattern. Each leaf is rolled in upon itself and at the same time enwraps the next leaf. It’s the closest thing to an archetypal process of unfolding you can imagine.

— original source: http://natureinstitute.org

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