Bicycle Botany: Skunk Cabbage

Skunk Cabbage (Symplocarpus foetidus (L.) Salisb. ex Nutt). 13 March 2013. Stroud Preserve, West Chester, Chester County, Pennsylvania

At long last, I took a ride on my bike that wasn't on my stationary bike in my basement. The last time that I did an out doors bike ride was sometime in November! Prior to that the longest break in bike riding was in 2007 when I dislocated my shoulder and broke my collar bone. Even then it was only for a bout 4 weeks. 

Excuses aside, it was great to get out for a 21 mile ride. As I rode my bike along Creek Road I saw one of my favorite sights of spring: skunk cabbage! Both the Pacific Northwest and the Northeast have skunk cabbage, albeit different species. The one that we have here in the northeast is Symplocarpus foetidus and the one in the northwest is Lysichiton americanus. While they both are in the same family (Araceae) and are commonly called skunk cabbage they are actually quite different. 

Skunk Cabbage (Symplocarpus foetidus (L.) Salisb. ex Nutt). 20 March 2013. Stroud Preserve, West Chester, Chester County, Pennsylvania. 

The reasons that I first became interested in skunk cabbage is that they employ a different strategy for pollination than most plants, and their name should give you some clue as to what strategy that might be. Their odor actually doesn't smell like a skunk. What it smells like is rotting meat and rotting meat will attract a whole bunch of insects, such as flies and beetles specifically, staphylinid (rove) beetles. Back in Washington when I would take a closer look at the flowers I would sometimes find 15 or 20 little black beetles on a single flower. Having come to the flower in the hopes of finding a meal of rotting meat, they find none and then move on to the next scent of rotting meat taking pollen with them. 

While pollination by carrion eating beetles is pretty cool, that is not the coolest thing I like about skunk cabbage. Actually the coolest thing about skunk cabbage is not cool at all. Skunk cabbage grows in northernly climates. Which, if you think about it, poses a problem if you are a large flowering plant that blooms very early in the spring and in wet marshy areas. The reason this would be a problem is that the surfaces of these wet marshy areas are often frozen solid in early March. The easiest way to deal with ice is to melt it, and this is exactly what the plant does. 

Skunk cabbage is one of the few plants that can produce their own heat, known as thermogenesis. And they don't just produce a little heat to melt the frozen ground, in fact, they can produce heat at temperatures that is 59-95° higher than the air temperature! Their ability to produce heat to melt icy habitats might be a lucky side product of the real reason they produce heat. 

Skunk Cabbage (Symplocarpus foetidus (L.) Salisb. ex Nutt). 26 March 2012. Stroud Preserve, West Chester, Chester County, Pennsylvania. This photo shows many plants which are only about 25% of their final growth. They can be up to two feet tall. 

Most plants that are thermogenic also depend on carrion loving insects for pollination. Most of these plants live in the tropics, where no icy habitats occur. The reasons why these plants produce heat is not clearly understood. It may be a way for the plant to produce additional vapors that enhance dispersal of the compounds that attract insects to them. This got me to thinking that if the plants are producing heat, they must also be producing infrared light. If so, they could also attract insects that see in the infrared spectrum. I don't know how if carrion eating insects see infrared, but I do know that insects that are hematophags (blood suckers) like mosquitos and bedbugs, can see the infrared heat of their victims.

As a side note, another interesting group of insects that can see infrared are the metalic wood-boring beetles (Buprestidae). These beetles see infrared for a different reason. They see the infrared heat produced by forest fires because they lay their eggs on charred wood. 

Regardless of the evolutionary pressures that caused these plants to start producing their own heat, they are pretty cool plants in my book. If you are on your bike this time of year, they are well worth the time to stop and take a break to check them out. Click on any of the photos above for a better view. 

Ride lots, and stop often!