Are Snowdrops Thermogenic?
Snowdrops are some of the earliest blooming flowers in my garden, often popping up through the snow, hence their name. We all love them for that, but how do they do it? I have been told several times that they are thermogenic, that is, that they produce their own heat, and decided to do some scientific research to find out (it can’t all be about pretty photos).
Over 200 years ago, French biologist, Jean-Baptiste de Lamarck, noticed that some flowers produce their own heat. Since then, scientists have confirmed that some plants can, in fact, generate their own heat, a process known as thermogenesis, previously thought to be limited to mammals, birds, and some flying insects. These plants are “warm-blooded”.
The poster child for thermogenesis is the eastern skunk cabbage, Symplocarpus foetidus, which is native to most of eastern North America. Its flower, pictured below (courtesy of Robert Klips, Ohioense: Bob’s Brain on Botany, March 8, 2010), heats up to melt the snow producing little circles all over the woods in late winter. It does this primarily to generate and disperse its floral scent to attract pollinators. In this case, the scent is rotten meat and the pollinators are flies and beetles. Secondarily, it rewards the insects by providing them with energy directly as heat rather than indirectly as nectar and pollen.
This is no small feat. Skunk cabbage flowers can heat up to 59 degrees F (15 degrees C) when the ambient temperature is 5 degrees F (-15 degrees C). They can also thermoregulate, adjust their temperature, to maintain a constant setting as the ambient temperature changes. If the outside temperature gets too low, they will switch off their heat entirely until things warm up. They also switch off the heat once they have been pollinated.
To perform thermogenesis, skunk cabbage uses as much metabolic energy as a small rodent or a hummingbird and employs a unique respiratory process, which is more similar to animal metabolism than plant metabolism though biochemical rather than nervous system based. The exact nature of this process is unknown. For those of you with a scientific bent, I have included a graph below taken from a scholarly treatise on the subject, Temperature Regulation by Thermogenic Flowers (Plant Physiology Online, Sept. 2006).
But, now that you understand thermogenesis, back to the question at hand: are snowdrops thermogenic? The short answer is I don’t know. Various sources say that they are, but the statements seem to be based on hearsay. I could find no scientific studies backing them up. I posted the question on the Pacific Bulb Society forum, the Scottish Rock Garden Club forum, and to friends at Longwood Gardens, and no one could confirm that snowdrops are thermogenic. So I present my own “scientific study” of the process.
As you know from my previous post, The Joys and Sorrows of Snow, we had record snowfall during the winter of 2009-2010. By February, my whole garden was covered by a deep, thick, hard layer of snow. Looking out on the landscape in the photo above, there was absolutely no melting going on except in three small areas. What is happening in those little circles? Let’s look closer:
And even closer:
My observations prove nothing scientific, but they do indicate that something is going on. And I like to think that one of my favorite plants, snowdrops, which inspire such intense interest in many gardeners, also produce their own internal excitement.
Please let me know in a comment/reply if you have any knowledge or personal experience with snowdrops being thermogenic.
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Nursery Happenings: I am currently accepting orders for snowdrops, including mail orders. For the 2011 Snowdrop Catalogue and order information, click here. I am also taking reservations for Charles Cresson’s Snowdrops and Other Winter Interest Plants Seminars. For the brochure and registration information, click here.