One of the earliest signs of spring is the Eastern skunk cabbage pushing up through thin ice and snow-covered ground. This remarkable plant actually produces heat as it grows. Look for it in early March while walking near swampy areas in woodlands or near creeks and ponds.
Skunk cabbage gets its name from the smell caused by crushing its leaves. These green leaves, which grow as large as 15 by 21 inches, appear later in the spring. In March, only the flowering part of the plant, called the spadex, emerges. The spadex is a tight cluster of small flowers on a fleshy stem. It is sheathed within a leaf-like, mottled reddish-purple hood called a spathe, which reaches up to 6 inches tall.
When the spathe is pushing out of the ground and generating heat, it also emits its distinctive odor. “There’s this very subtle, soft, pungent, skunk-like smell in the air,” says Craig Holdrege, director of The Nature Institute in Ghent, New York, who has observed skunk cabbage in his region for two decades. “Then I know I’m there at the right time (to spot the spathes coming up). I sometimes smell them before I see them.”
If light snow dusts the ground, “there will be a little ring around the plant where the snow has melted—maybe an inch of snow-free area encircling the spathe,” Holdrege says. If the snow is up to about 6 inches deep and the tip of a plant is sticking through, he sometimes digs down carefully and finds a cave where the skunk cabbage has melted the snow around it.
“It radiates out heat,” he says. If you gently put your finger inside at the base, “your finger will actually warm up.”
Like a Mouse
Skunk cabbage generates warmth by breaking down starch that it has stored over the winter in its roots and rhizome, or underground stem. In a process called thermogenesis, it uses oxygen to break down sugar, releasing heat.
“It’s basically doing what we do” but on a smaller scale, Holdrege says. It’s behaving physiologically like a mammal.
The skunk cabbage can keep its temperature fairly constant at about 60 to 70 degrees Fahrenheit for a week or two in early spring, even if the outside temperature is fluctuating. Once this crucial period is over, it stops generating heat. It is the only plant in our region that has this capacity.
Some scientists think that the Eastern skunk cabbage generates heat to disperse its scent and attract pollinators. Skunk cabbages do attract the first insects of spring, which enter the spathe to warm up and feed on pollen, helping the plant procreate. Another theory suggests that the heat is beneficial because it helps protect against frost damage, allowing the skunk cabbage to germinate and sprout earlier than other plants.
Whatever the evolutionary advantages, the skunk cabbage is “making spring happen earlier than it would otherwise,” Holdrege says. “It is the first harbinger of spring, before you have any feeling that spring is near.”