Bug o’the Week
by Kate Redmond

And Now for Something a Little Different Eastern Skunk Cabbage

Greetings, BugFans

While you’re still paying attention, let’s get this correction out of the way.

Nota Bene:   The BugLady misread an email from BugFan Tom, who supplied the photographs for the recent episode about Black widow spiders.  Tom can leap tall buildings in a single bound, but he does not handle Black widow spiders.  If you passed that episode along to a friend, please send this correction after it.

This episode started out many years ago as an article that the BugLady wrote for the BogHaunter, the newsletter of the Friends of the Cedarburg Bog, but she rewrote it.

The BugLady visited one of her favorite wetlands the other day, looking for spring.  It’s early days for flowering plants around here (and for insects, other than flies), but our two earliest wildflowers – pussy willows and skunk cabbage – are happily doing their thing.  It will be a little while before the flowering plants in the wetlands start to bloom, but mosses and liverworts are putting on a show ahead of that, and soon the fern fiddleheads, lichens, liverworts, and horsetails/Equisetum will join the chorus.  Nothing beats the smell of a wetland!

Skunk cabbage (Symplocarpus foetidus) (Symplocarpus foetidus means “clustered fruit that is fetid,” and isn’t that awesome!) is a member of the Arum family, Araceae (culinary cabbages aren’t).  There are more than 3700 Arum species worldwide, mostly tropical, and the members of the family that grow in and around our area wetlands – skunk cabbage, Jack-in-the-pulpit, and wild calla (plus arrow arum in a few parts of the state) – are some of our oddest-looking wildflowers.

Arums are famous for their decadent odor, for containing calcium oxalate crystals that make eating them painful and even dangerous, and for the ability of many species to produce heat.  They are not poisonous to touch, and both the odor and the crystals discourage (most) grazers.  Familiar houseplants like dieffenbachia, philodendron, and calla lily are also members of the Arum family, and all contain calcium oxalate crystals, so keep an eye on those plant-munching toddlers and cats. 

Skunk cabbages are like Russian nesting dolls.  Small flowers sprout from a fleshy, spherical structure called the spadix, and the spadix is enclosed in a maroon, hood-shaped spathe (there are populations with greenish spathes and with variegated green and maroon spathes, too).  After the flowers have bloomed, the spathe will be dwarfed by big (18” to 36”), cabbage-like leaves.  Smelling a pinch of the spathe or of the leaves in spring will explain the plant’s name. 

Heat is generated when the plant uses oxygen and an aspirin-like substance to break down stored starches. “To produce heat,” say the folks at the In Defense of Plants website,“the spadix is hooked up to a massive underground energy reserve largely in the form of carbohydrates or sugars.”  Skunk cabbage blooms right at ground level, so the heat it produces can melt the spring snow around it, and the heat broadcasts the plant’s pungent odor. 

The Styrofoam texture of the spathe insulates the spadix.  Wind that enters the spathe circulates in a vortex that keeps the inside temperature stable.  When the soil temperature reaches 32 degrees F, the respiration of the spadix warms the inside of the spathe to a constant temperature of about 72 degrees F (and as high as 90 degrees F) despite the ambient air temperature.  One source mentioned warming one’s hands over the spathe. 

Blooming before many flying pollinators emerge, skunk cabbage’s rotten odor and liver-colored streaks attract carrion-seeking flies and small beetles to the tiny yellow flowers on the spadix (it’s called “dung mimicry”), and insects that come for the carrion may stay for the heat.  Early-foraging honey bees and other insects visit the spathe to warm up, and, incidentally, pollinate the flowers.  Opportunistic spiders sit on the spathe or spin webs across its opening.

Skunk cabbages grow from thick, underground stems called rhizomes or rootstalks that put out both roots and leaves.  Skunk cabbage may grow for a very long time – potentially for centuries if its habitat isn’t disturbed – and its root systems can get so extensive that it’s almost impossible to dig up.  The rhizome of an older plant can be a foot thick.  Its roots are “contractile” – after the plant blooms, the roots contract slightly and keep the plant snug against the soil.

It likes to grow with its feet in or near the water, with spathes sprouting from wetland hummocks and sometimes emerging semi-submerged in standing water.  Like the habitat that surrounds it, the tissues of its leaves and flowers are very watery, and they decay quickly.  

Each skunk cabbage flower has both male and female structures, but they’re not self-pollinating.  The female parts bloom first and then become unreceptive as the male structures at their base start releasing pollen.  The fertilized flowers on the spadix form a compound, berry-like fruit that reclines on the wetland floor where the seeds will be released to float away or to germinate near the parent plant.

During a long, mild fall, skunk cabbage sends up green, cone-shaped flower buds – ready for the following spring, when the dance will begin again.

Despite the calcium oxalate, Native Americans used skunk cabbage rhizomes and leaves as food and medicine, but only after neutralizing the calcium oxalate by drying the plant or by lengthy cooking.  BugFan Mike once told the BugLady that skunk cabbage is listed as an emergency food, but in order to disarm the crystals, the leaves must be boiled in successive changes of water until the water in the pot no longer has a “bite.”  Mike said that after all that boiling, the leaves were about as appetizing as a wad of wet Kleenex (the moral of the story is that if you’re going to get lost and need to eat skunk cabbage, be sure to have a large pot and lots of water at hand).  It was used as a medicine to treat toothaches, asthma, bruises, blisters, scurvy, headaches, and more.  The fresh root of skunk cabbage is toxic, but it’s rarely fatal because it tastes so bad that it would be hard to eat a lethal amount. 

And it’s used by wildlife – muskrats browse on the unopened spathes in early spring, and the young leaves and flowering structures are favored by bears, snapping turtles, turkeys and geese.  Snails and slugs graze on the leaves; the seeds are eaten by squirrels, Wood Ducks, Ruffed Grouse, quail, and pheasants; and millipedes and sowbugs feed on the decaying vegetation.  Maryland Yellowthroats nest in its dense thickets, and the BugLady found a funnel-web spider that spun its web in the angle of the leaves.

The BugLady is always amazed at how frequently she finds an emerging skunk cabbage leaf that’s trapped in a dry leaf from last fall – amazed first because of all the stars that have to align in order for the tip of the skunk cabbage leaf to insert itself into a random tear in the dead leaf above it, and amazed because these robust leaves can’t seem to burst out of their fragile bonds.

Thoreau wrote that the opening of the spathe usually faces south, but research does not confirm this.  In the BugLady’s experience, the opening usually faces away from the boardwalk she’s standing on.  

Yes, there is a Western skunk cabbage – https://budburst.org/plants/211

Kate Redmond, The BugLady

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