Secrets of the Skunk Cabbage
In early spring, before just about anything else has started growing, you might notice strange, purple pods poking up in marshy environments - or straight through late season snow. This is the skunk cabbage, a plant that has developed a wild adaptation to let it beat the competition to the growing season.
EPISODE NOTES
TRANSCRIPT
Bright green buds nosing their way out of tree branches. Innocent little shoots poking up from the thawing ground.
Spring is a joyous symbol of revitalization and regrowth. The reassertion of life after a cold, dead winter.
But every one of those plants nudging its way skyward is after the same thing: nourishing sunlight. And there’s only so much to go around. One plant growing taller and spreading more leaves sooner can mean starving its neighbours in the shade. And if you come up late and slow, you’re the one starving.
So what we’re also looking at here is a no holds barred battle for real estate and resources.
That means it really pays to be on the scene as early as possible. So much so that certain plants have developed wild adaptations to beat the competition.
Like one of the earliest spring arrivals: the skunk cabbage. Emerging looking like purple alien pods, they’re so early on the scene that you might actually see them growing straight through late season snow.
And that right there illustrates their big advantage. While other plants are stuck waiting around until the ground defrosts and the snow melts away, skunk cabbages… can just melt it themselves.
It all comes down to this. It’s a spadix. Which is actually a concentrated grouping of flowers without petals - we’ll come back to that part.
For now, what you need to know is that the skunk cabbage uses its spadix for thermogenesis.
The bio-chemistry of all this is… admittedly kind of over my head. But I’m going to try to do justice to a simplified form.
Plants use energy from sunlight to produce glucose from carbon dioxide and water. That’s photosynthesis.
Then, the energy from that glucose is released as ATP - the primary energy carrying molecule in all living cells. This release of energy is called cellular respiration.
With me so far? OK - so, plants also have another pathway that glucose can take, called cyanide resistant cellular respiration. This results in less ATP being produced. Most plants use it for energy regulation.
But a very few plants have a supercharged version of cyanide resistant cellular respiration. They can divert 75-90% of their respiration to this pathway. Our skunk cabbage is one of those plants.
What does that mean? A lot of energy that is not being converted to ATP.
But, the energy has to go somewhere. And so instead is gets released… as heat.
A lot of heat. Skunk cabbages can raise their local temperatures 15-35 degrees celcius with this process. That’s thermogenesis.
And that lets them melt their way through the frozen ground and snow to be the first ones up in the spring, their heat-drill spadix protected in a specialized leaf called a spathe, before they expand to a huge collection of broad leaves - getting all the real estate they can before anyone else shows up.
Genius. Amazing plant. But - there’s no such thing as a free lunch. Being first out of the ground in the spring may mean you’re going to get first dibs on all that sunlight, but it comes with two pretty big challenges too.
One: you still need to do your evolutionary duty and reproduce. But how do you attract pollinators when almost all of them are still in winter torpor?
Two: if you’re the only plant life poking up through the frost, that means you’re one of the first available food sources for starving herbivores coming out of hibernation or just at the tail end of a hard winter.
Let’s start with reproduction, which takes us back to the spadix. I mentioned that it’s actually a conglomeration of flowers without petals - which is actually a clue. Showy flowers are there to attract pollinators, so the fact that these flowers are hidden in the spathe without petals tells us the skunk cabbage is attracting them in a different way.
The answer is actually in the name - skunk cabbages smell. They give off an odor that, to insects, is reminiscent of carrion - just what they’re looking for. And it’s possible the heat of the skunk cabbages helps sell the illusion. together they attract pollinators without the need for flower petals. Those pollinators fly into the spathe, land on the spadix, pick up pollen, and move to the next skunk cabbage. Reproduction problem: solved.
As for their vulnerability as the first edible plants out of the soil in the spring? Well, they’ve made themselves totally unpalatable. In another adaptation, skunk cabbages cause a strong inflammatory response in the mouth and esophagus when eaten - enough that any animal who tries a skunk cabbage meal is unlikely to try again.
A plant that can melt its way through snow and ice is crazy. But the lesson here is bigger than that. It really shows the unrelenting race of evolution.
Every advantageous adaptation can reveal new challenges - which require new adaptations, which bring new challenges…
So to look at the specializations of any organism is like flipping back through that history of give-and-take, move and counter-move, across evolutionary time - leaving us with the unique brilliance of the humble skunk cabbage.