Skunk cabbage; a warm-blooded plant?

In Uncategorized, Winter by couchiching

We look for the blossoms of crocus and snowdrops as signs of spring, but those who want to hurry the season can hunt for eastern skunk cabbage (Symplocarpus foetidus).

Their flower heads will manage to poke through the snow by mid-March, or even earlier. At the T.C. Agnew Nature Reserve on Sunday, March 22, a number of skunk cabbage were found with small, green, tapering hoods, called spathes, poking 5 to 8cm above the ground. As they grow the spathes will change colour to a mottled plum. It’s usually the earliest bloomer in our woods.

The skunk cabbage flower is not resistant to frost. To emerge so early, it has to beat the cold. So astoundingly, it produces heat—enough so that the snow is often completely melted around it. Measurements show it produces heat up to 35°C warmer than the air around it. The flower head can thaw frozen ground to emerge into the waiting world, even this spring when the thermometer has refused to cooperate with the season.

How? It’s a rare trick called thermogenesis. The skunk cabbage uses oxygen to produce heat. The oxygen reacts with starch from the root, breaking molecular bonds apart to release energy in the form of heat. One study estimated skunk cabbages consume as much oxygen as mammals of the same size.

The colder the temperature, the more oxygen it breathes in and the more heat it generates, until spring finally warms the woods up. A few other plants can produce their own heat, but none with skunk cabbage’s talent for cranking the heat out for weeks on end.

The heating process has another advantage: it helps intensify the flower’s rank odor, described as a combination of rotting meat, apples, turnips and garlic. It’s a perfume guaranteed to attract attention, and early emerging honeybees and other flies are glad to smell it. The lure brings them to flower stamens loaded with pollen, ensuring the flower is fertilized and produces seeds.

Something had been nibbling at the tips of the flowers at T.C. Agnew Reserve—likely mice, judging from the delicate bites. It’s not a great idea to chew on raw skunk cabbage; the tissues contain calcium oxalate, the same ingredient that makes rhubarb leaves and calla lilies toxic. Since skunk cabbage is the first plant to produce green growth in the woods, this is a clever defence against being devoured before it can finish blooming. Some animals must be able to deal with the toxin, though. Bears have been seen dining on the leaves; in some areas of the U.S., the plant’s common name is bear-weed.

Below ground are even more surprises. The skunk cabbage root is a thick rhizome with a mass of thin roots branching from it. These lateral roots are “contractile,” meaning they can pull the plant deeper into the ground. This may seem odd, but with the heaving, freeze-and-thaw cycles and seasonally wet areas these plants prefer, this anchoring tool must be very handy. The huge root system is also a superb energy storehouse for the plant’s little furnace. After several seasons of growth, a skunk cabbage root is almost impossible to dig up.

The plant’s smell prompted people to give skunk cabbage its uncomplimentary name. But given all its ingenious survival tools, a more fitting name would be the Da Vinci plant.

Written by John Challis.