Kindling Neighborly Connections between People and Nature.

Thursday, February 13, 2020

Warm Wild Neighbor: Skunk Cabbage

Pine Creek Rail Trail (near northern terminus) 2/13/2020  9:34am-11:02am
Skunk cabbage unopened leaves (left) and flower head (right)
The clouds are lying so thick this morning that the tops of the hills in the Asaph Wild Area are concealed as if by a thick veil. With temperatures in the mid 30's I can't tell if it wants to rain or snow. Thankfully right now its doing neither.

As I make tracks in the snow on the Pine Creek Rail Trail I'm in search of skunk cabbage; a warm, pungent, uniquely structured expression of Divine creativity that has a habit of blessing the wet low lying areas of the forest with its presence earlier in the year than any other flowering plant in this region.

Half-a-mile along the rail trail from the Stokesdale parking lot, I'm taking note of a couple of blue jays, a distant flock of crows, nuthatches, titmice, and a mourning dove that's singing.

About three-quarters of a mile from the trailhead, I chose to veer left on a side-trail just before the wooden fence begins where a bench sits on the side of the path. This narrow trail leads into the wooded marsh beneath a canopy of leafless black willows.

About 70 paces from the rail trail; a good sign. The spore carrying shoots of sensitive fern stand in densely packed clusters. These ferns are dormant yet holding clusters of spores that are looking ripe for dispersal. Sensitive fern is a species that shows a preference for wet low-lying forested areas. The same habitat preference as skunk cabbage. The ferns are here, and the cabbage should be too.
Skunk cabbage and sensitive fern
A few more paces and Ah! Sure enough right there at the water's edge I've spotted the first one. Just one look, and the structure of skunk cabbage is intriguing; shaped like a small dwelling, pointed at the tip, with an open door in the front within which the flower head (inflorescence) takes refuge. Standing in place for about five minutes I'm able to take note of about 20 more skunk cabbage plants within about a 10 foot radius. Some protrude straight up out of the shallow water. Others emerge from the mud and poke through the snow, or rather, melt the snow around them.

Skunk cabbage emerging through shallow water
Skunk cabbage emerging through the snow

That's one of the most fascinating things about the skunk cabbage, its an endothermic plant, capable of producing its own heat that is warm enough to melt the snow that sits above the newly emerging flower head.

Here is some information about the endothermic nature of skunk cabbage from a book I've been reading, titled Ecology Concepts and Applications: Fourth Edition

"Almost all plants are poikilothermic ectotherms [organisms that don't regulate body temperature and are therefore dependent upon the temperature of their environment]. However, plants in the family Araceae have the unusual habit of using metabolic energy to heat their flowers. Some of the temperate species in this mostly tropical family use this ability to protect their inflorescences from freezing and to attract pollinators. One of the most studied of these temperate species is the eastern skunk cabbage, which lives in the deciduous forests of eastern North America. This skunk cabbage blooms from February to March, when air temperatures vary between -15 degrees C to 15 degrees C. During this period, the inflorescence of the plant, which weighs from 2 to 9 g, maintains a temperature 15 degrees C to 35 degrees C above air temperature. As Knutson [scientist Robert Knutson] observed, this temperature is warm enough so that S. foetidus can melt its way through snow. The plant's inflorescences can maintain these elevated temperatures for up to 14 days. During this period, it functions as an endothermic organism. How does the skunk cabbage fuel the heating of its inflorescence? It has a large root in which it stores large quantities of starch. Some of this starch is translocated to the inflorescence, where it is metabolized at a high rate, generating large quantities of heat in the process. This heat, besides keeping the inflorescence from freezing, may help attract pollinators. Various pollinators are attracted to both the warmth and the sweetish scent given off by the plant...The inflorescence of the skunk cabbage maintains a high respiratory rate, equivalent to that of a small mammal of similar size. However, its metabolic rate is not constant. The plant adjusts its metabolic rate to changes in environmental temperatures. The metabolic rate increases with decreasing temperature, which increases the rate of metabolic heat production. By adjusting its metabolic rate, the plant can maintain its inflorescence at a similar temperature despite substantial variation in environmental temperature." (Ecology Concepts and Applications: Fourth Edition. Manuel C. Molles Jr. McGraw-Hill Companies; New York, NY 2008. Page 99)
Snow melted by skunk cabbage

Skunk cabbage inflorescence with pollen
When snow covers the ground in February in Pennsylvania and you're in the skunk cabbage's habitat, just look for holes in the snow cover. A newly emerging skunk cabbage flower head may have created that hole in the snow with the warmth put out by its body.

If you're as curious as me, go ahead and stick your finger inside of the opening in the pointed cap; on a cold day you can feel the heat! If you want to know how skunk cabbage got its name, then after you've touched the cap or flower head go ahead and smell your hand. It's not so bad, and I can honestly say that I've developed an appreciation for every part of it, including its smell. That being said, this is probably not the kind of flower to bring home for your significant other on Valentines Day.

Skunk cabbage inflorescence (no pollen yet)

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