Are Snowdrops Thermogenic?

Galanthus ‘Dionysus’, a Greatorex double

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The 2014 Snowdrop Catalogue, featuring snowdrops and other winter interest plants like cyclamen and hellebores, is on the sidebar, and we are taking orders, to access the catalogue please click here.

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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).

Common snowdrop, Galanthus nivalis, and “spring-blooming” hardy cyclamen ‘Rose’, Cyclamen coum ‘Rose’, in my rock garden

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”.

Holes in the snow produced by eastern skunk cabbage, Symplocarpus foetidus, performing thermogenesis, photo Robert Klips

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.

Eastern skunk cabbage blooming through the snow, photo Robert Klips

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.

Eastern skunk cabbage peeking out of its snow cave, photo Robert Klips

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).

Graph of oxygen consumption and heat production by skunk cabbage in various ambient temperatures

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.

February 21, 2010, at Carolyn’s Shade Gardens, three tiny islands are appearing in the snow

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:

Giant snowdrop, Galanthus elwesii, melting through the snow


And even closer:

Giant snowdrop blooming in February after melting through the snow pack

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.

For my previous articles on snowdrops, click here and here.


Please let me know in a comment/reply if you have any knowledge or personal experience with snowdrops being thermogenic.

Carolyn


Notes: Every word that appears in orange on my blog is a link that you can click for more information.  If you want to return to my blog’s homepage to access the sidebar information (catalogues, previous articles, etc.), click here.

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.

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96 Responses to “Are Snowdrops Thermogenic?”

  1. How utterly extraordinary. A plant that can auto regulate its temperature? And certainly strong circumstantial evidence that snowdrops are thermogenic too. Thank you, a fascinating post.

  2. Dear Carolyn, Well…one learns something new every day. I have no idea whether Snowdrops are thermogenic or not but I like to think that they are. These brave little plants make an appearance in the most inhospitable conditions that I like to think of them having their own ‘electric blanket’ under ground to keep them warm.

  3. Definitely worth studying. You should find some enterprising hort grad student and sponsor a paper.

    • Susan, It’s so funny how it happens that you have been told something over and over, but when you look into it there’s no concrete basis for the statement. It happens all the time to me because I produce my plants for the nursery by growing them in the ground. Theories about plants that are developed by people who grow them in pots in greenhouses often turn out to be wrong. This would be a good research project. Carolyn

  4. gardeningasylum Says:

    Really interesting post! My snowdrops have been a bust, but I’ve observed my lysichiton – has it recently been renamed? – popping a hole through the ice at the edge of the frog pond – now I know how!

  5. Fascinating, I was surprised to see you on the srgc forum. I have been a ‘lurker’ there for a few years. I wonder about helleborus as well, I often find them flowering, surrounded by snow.

  6. Science statements can start by a hypothesis, such as yours. I have no experience but your “experiment” in two years in a row should, at least, offer material fo a paper as Susan mentions. Now you have me thinking….

  7. fasinating Carolyn, I would never have imagined, thanks for another interesting post, Frances

  8. I had not heard this before and will have to watch closely as the snow melts…

  9. Marcia Meigs Says:

    Hello Carolyn, What a fine article and thank you. I will be checking the creek area down by the road where we have to abandon the 4 wheel drive Jeep and AW drive Suburu and struggle up the drive. Your discerning eye and intelligence inspire me. I will be checking the galanthus more often to see which ones come out first, although I am hoping they stey put until the weather settles a bit, perhaps in three or four weeks. I do find that only some galanthus are happy emerging too soon and the blooms suffer at which point I run around with glass cheese domes, cake domes, etc. to cover the more tender plants. Even the smaller and more favored peonies get trash cans placed over them as the buds do suffer.
    Your blogs surely do lighten the megrums of Winter hibernation here in Ithaca.
    Marcia

  10. Dear Carolyn, Warm-blooded plants … who would have known! Always good information here. P x

  11. Carolyn – So you are a plantswoman and a scientist … really interesting post. I started off wondering where the plants would get their heat from, if the theory is true, but then I realised I don’t know where mammals get their heat from. Can’t stop thinking about it now …

    • B-a-g, I am certainly not a scientist, and my observations prove nothing, but it’s certainly fun to think about. Follow the link to read the scientific article, which explains the processes involved in overwhelming detail—it took me a couple of tries to figure it all out. Carolyn

  12. A well researched and interesting post Carolyn. Poor old skunk cabbage – could the namer not have given it something less off putting. Not sure if your snowdrops are thermogenic but certainly they are photogenic.

    • Laura, The flowers really do smell like skunks or worse, but the name hasn’t helped the plant very much. I have always loved it, but it is held in generally low regard here. Good play on words. I have a feeling that photogenic may be all snowdrops are, but I’m still looking into it. Carolyn

  13. Very cool. I would hazard the guess that your snowdrops are thermogenic. I will keep out an eye for my snowdrops and see if they melt snow.

  14. Judith Spruance Says:

    Great blog! I have always loved seeing the skunk cabbages spiraling up in the early spring and it is extraordinary to learn about their being thermogenic. And I’ll be checking my snowdrops for this too. Just when we thought the winter landscape was getting dull, we have some exciting research to do out there. Thanks

  15. I’ve never heard of this phenomenon before, what an amazing attribute!

  16. This is interesting! Thank you for the research and the sharing of your experience.

  17. Fascinating! Thermogenesis is an utterly new concept for me. Great, great article! Now I want to go out and find out plants that my produce heat.

    Where is the snow when you want it.

  18. hi Carolyn, you are generating really lots of excitement, and it’s surely fun for everybody. As you know, we dont have snowdrops, but i saw it once in Turkey when at the middle of a symposium someone asked who wants to go with them to the snowdrops festival. So we were absent that day in the conf to go to the mountains to look for snowdrops. I’ve posted this last year. Fortunately, a paper was also discussed about it in our session about its shelf life. Maybe he knows what you talk about. He is a scientist in Mann Lab, UC Davis, Dr. Michael Reid. BTW, if there are thermogenics, there is the opposite which i dont know the term, maybe cryophiles??? haha. I refer to warm blooded animals which hibernate in winter. Lastly, we have an equivalent here for your skunk cabbage, here they just produce early flowers after the rain following long dry season. We cut it immediately before opening to not let them emit those foul rotten meat odor. This plant is Amorphophalus campanulatus.

    • Andrea, I wish I was with you in Turkey seeing snowdrops in the wild. You were so smart to skip the conference and have that experience you will never forget. I will look for your post. I will also see if Dr. Reid has published anything. I remember there was research done on this in California. The plant you mentioned is in the same family with skunk cabbage, the aroid or arum family, Aracaea. Carolyn

      • Carolyn, i found somewhat logical explanation for the melting snow around growing snowdrops: …part of the reason the snow might melt around it is just simple absorption of light. White snow reflects light really well – anything darker will absorb more of it and therefore be warmed up. You can see this with dark-colored rocks quite dramatically. (from dracoi’s comment in http://boards.straightdope.com/sdmb/showthread.php?t=554167). Thanks.

      • Andrea, You really have gotten interested in this. I read that discussion when I researched my article. That might explain why the snow melts more readily once the snowdrops are through the ice. But the snowdrops in my photo are completely covered by evergreen ferns and hellebores, which would absorb heat even more, yet the only place that melts is where the snowdrops are coming through. Let me know if you find anything else. Carolyn

      • I searched on Michael Reid’s works, but he worked more specifically on shelf life or postharvest, so his name is not related with thermogenesis. Also went back to the Turkey Proceedings of ISHS and realized he just presented his paper on snowdrops informally to use the time of a speaker who did not show up. Am sorry about that, just realized it when i gave some deeper thoughts. Have you seen http://www.digitalbotanicgardens? Phil is a botanist and might know more about thermogenesis. I am sure he knows more about respiration and mitochondria, hahaha!

  19. The skunk cabbage emerging looks like gnomes!

  20. Great post, Carolyn, thank you. I thought you might be interested in John Grimshaws blog (just in case you haven’t seen it!) http://johngrimshawsgardendiary.blogspot.com/ He has several posts on snowdrops. I thought the one called First lessons from the ‘New Testament’ would be of special interest.

    Best wishes Sylvia (England)

  21. Hello Carolyn, recent information which I read recently was that when snowdrops are in bloom and the temperature plummets, the flower closes and a form of antifreeze emits protecting the bloom. Very simplistic and not quite the information that you are looking for. What about the skunk cabbage saving the world by producing an alternative heat source, well perhaps not.

    • Alistair, Would love to have some more information about what you read about snowdrops. Believe it or not, the same thought occurred to me about the skunk cabbage. Why couldn’t that process be harnessed to produce heat on a bigger scale? I think it might be the that the amount of energy used by the plant to produce the heat cancels out the benefit. Carolyn

  22. Fascinating post Carolyn! I like to think of them as warm green-blooded! I think they must have little comforters around them. Mother nature could not be such a bad mother not to care for her earliest flowers. Silly I know. They are the bravest little plants.

  23. I am a great one for liking pretty pictures, but do agree that it is nice to have something else to offer in a blog post. I had no idea that some plants had their won central heating system! How interesting. I have noticed little islands in the snow and this explains it. I would hazard a guess that you are right about the snowdrops.

  24. Carolyn your post is absolutely fascinating. I’ve never heard of this before but it certainly stands to reason. I look forward to reading more about this.

  25. Fascinating! Blogs are such a rich source of information and beauty.

  26. How interesting this scientific findings about plants being thermogenics, the first time Ive heard about it! Its quite fascinating, great post Carolyn!

  27. Carolyn, thanks for the visit to my Hamamelis post and especially the information on Arnold Promise. I really appreciate comments like this I will put this information on my post. Nothing more to enlighten you on the Snowdrop, one of those casual reads that one does without taking enough details.

  28. Wow Carolyn! This is fascinating. Now I want to plant skunk cabbage all over my yard and do a snow dance. We only get one or two snows per winter, so I’m not sure it would be worth it for me. Thanks for sharing this!

    • Eliza, Skunk cabbage are very cool plants even if you don’t have snow for them to melt. They bloom so early—great winter interest—and their leaves are huge and tropical looking. Being ahead of my time, about 15 years ago in my horticulture class full of upscale gardeners, I opined that I loved skunk cabbage, and we should think of them as the American hosta. Well the reception for that was chilly at best. Now the more ornamental skunk cabbages are all the rage. Carolyn

  29. Dear Carolyn, this is a very interesting post! I had no idea plants could do this. The more we learn about plants the more fascinating they are. I suspect there are amazing complexities within the natural world that modern scientists have yet to discover.

    BTW, I so appreciate the comment you made on my mahonia post! You are a great resource. If you haven’t already, you may want to read the follow-up post, ‘My Decision’. I mentioned you in it.

  30. Carolyn, Cat, and pschandan, I had no idea that people didn’t know about this process and am so glad I was able to outline the basics of this interesting phenomena. Carolyn

  31. Plants have so many adaptive responses to their relative environments, you can’t help but admire them!

  32. I know you have had a gazillion comments, but I would be too remiss not to add mine. This was so so very interesting and informative. Hundreds of snowdrops have broken ground and now I know they are heating things up. Hmmmm, perhaps it is advantageous to a small mammal to hang out near these plants, especially large colonies as the natural tendency to multiply. I think I’ll go check that flowerbed for moles.
    nellie

  33. I have not Idea whether Snowdrops are thermogenic, or not, but that was a really interseting section on the skunk cabbage!

  34. I didn’t even really know what thermogenic was until your post! How fascinating. I just adore snowdrops. Thanks for the post!

  35. What a fabulous post and judging by all these comments I’d say everyone agrees. I love your own scientific study. I’m thinking yes the snowdrops must be thermogenic. Not measure how much they can heat up and how much energy they use. That should be fun.

    I grew up in Maine and loved the skunk cabbages. I had no idea about the heat they generate. They are the coolest plants. I have not seen any down here so I’m not sure if they are down here but I don’t see why they wouldn’t be. It’s amazing how they stand out in the snow. Too awesome.

    Your research is well appreciated and very thorough. Awesome pics to:)

    • Tina, I looked skunk cabbage up on the USDA plant profile and it shows them native to the counties in the far northeast corner of your state. Not sure where you are though. They are very cool. I have never seen them for sale though only the species with the yellow flower, which I think is native to the Pacific Northwest. Carolyn

  36. Northern Middle Tennessee so that explains it. I figured it was not cool enough here. In Maine they grew along ponds and streams and there were alot. You brought up a good memory of these lovelies. I’ll look for them if I go to the mountains. Thanks for taking the time to look them up for me.

  37. My snowdrops bloom a lot later than yours-mid-March, usually. I am going to watch them more closely to see if they do the melting trick. I had heard about the heat generating properties of skunk cabbage but had never seen a photo that illustrated it so well.

    • Kathy, There are different species of snowdrops that bloom from October into April. The snowdrop in my GBBD photo is Galanthus elwesii, which is the first snowdrop to bloom. If you have G. nivalis, the most commonly grown snowdrop, it blooms in late February to March here. Carolyn

  38. What?? I had no idea plants could do this. Thanks for the new info!

  39. Your articles have been really great! I think I’ve been bitten by whatever magnet you have forcing me into your catalog…I’m going to order some snowdrops and probably some other items! I’m really happy to find out that it’s not too late and that you are offering them:-)

    • Jan, I like your enthusiasm but not the word forced. If you are looking for mail order, the only thing I ship is snowdrops. However, I am having an informal get together of bloggers at my nursery this spring if you are interested. No date yet. Keep in touch. Carolyn

  40. ‘forced’ was maybe not the best choice of words…I just meant that I was very drawn to it.

    • Jan, I was only kidding. I am sorry if you thought I was serious. I was actually quite flattered because you are the first blogger who has mentioned my catalogue and the whole other side of what I do. It’s obviously not what I push in the blog, but it’s a lot of work and a business I created myself. Carolyn

  41. Hello Carolyn,
    Found your snowdrop thesis today, having only heard about skunk cabbage info. about 2 weeks ago. I find it fascinating, being very interested in insects, and their vital role in biodiversity in our gardens at the base of the food chain, and that when the plant hunters brought plants across continents, the native pollinating insects would have been left behind in their endemic environments. Equally how few insects are ever about in our garden at the time these early spring flowers actually flower… hence pretty poor seed production unless you hand pollinate, but would love it if one could detect a significant temperature change within the flower ( over the simple shelter from wind , etc. within the centre of the flower itself). Great site, love it. Julian

    • Julian, It is all pretty fascinating, but I still haven’t found any scientific evidence for thermogenesis in snowdrops. Seems to just be conventional wisdom. Carolyn

      • Hello Carolyn,
        I went out today with my digital point and shoot thermometer ( ? infra red/ ? laser ) and seemed to consistently get a 1. 5 to 2 degree centigrade higher temperature on the outer surface of the white central ‘tube’ of inner petals , when compared with the green ? ovary or base of the flower. Being darker in colour I might have expected it to be the other way round. Of course it could just be because the inner column of trapped air inside the petal tube has more of a chance to warm up. 2 deg.c is not great, but I guess when ambient temps are only 5 or 6 deg.C as today, it could affect the ‘scent or appeal’ of the flower from an insect’s point of view.

        Julian

      • Julian, It is so wonderful that you took the trouble to do this. Another reader sent me an article for the December 2010 issue of Gardener’s World magazine which states that the snowdrop’s inner bell is 2 degrees warmer than the outside temperature but cites no source for the information. It seems that you have provided some evidence for this. Thank you for taking such an interest, Carolyn

  42. Hello Carolyn,
    My final comment on this subject, which you might like to follow up, is a link to a wonderful article I’ve just found on Google entitled ‘Warm Flowers, Happy Pollinators ‘ by Heather Whitney and Lars Chittka, which covers some fascinating quite recent research in this area relating to insect pollinators.
    Thanks again for sparking off the research, with your snowdrop blog,
    Best wishes
    Julian

  43. Hello Carolyn,
    Inspired by your site, and your cv, I’ve taken the plunge and just set up a blog on word press, with my first rushed post on crocus questions tonight. I clearly have a steep learning curve… at :
    thegardenimpressionists.wordpress.com,
    Best wishes
    Julian

  44. [...] I am not digging through the snow to see if they've sprouted. (So far, no sign of thermogenesis.) But, at the southern-exposed intersection of driveway and road, “the postcards from [...]

  45. This post is the first page to come up during a Google search for “thermogenic snowdrops.” It looks like there’s a lot of anecdotal evidence, but with a plant as popular as snowdrops, I was surprised it hasn’t been tested scientifically. From your pictures, it does appear that something is happening. Many plants are tolerant of extreme cold, and it could be that this one produces and releases a compound that lowers the melting point of water, similar to salt.

    • Owen, I have been wracking my brain for months trying to come up with the term anecdotal evidence, which is the perfect way to describe what exists about snowdrops being thermogenic. I too am surprised that all those European galanthophiles have not experimented with this but apparently they haven’t. Thanks for commenting. Carolyn

  46. [...] These are G. nivalis from the secret garden at the old house. It looks like they are exhibiting thermogenesis–creating their own [...]

  47. [...] good old fashion winter so – No there are no bulbs pushing out of the ground.  There is no  thermogenesis–plants creating their own heat and melting the snow around them.   My front garden is still [...]

  48. Ellen Bell Says:

    Here in Iowa we still have several inches of snow and there are little melted circles around the snowdrops. Thermogenesis is a great new word. Thanks,

    Oh I have a picture if you’d like.

  49. Dr. Stefan Riegel Says:

    The little circles in the snow can also be seen around other plants and even dead objects in the snow. They are simply caused by shielding the surrounding of an object during snowfall and subsequent sublimation of the snow at this boundary surface, what makes the circles get larger with time.

    I asked the worldbest expert on snowdrops, Aaron. P. Davis from Royal Botanic Gardens Kew, for his opinion on the thermogenesis question. Davis replies: “I know of no scientific research supporting these assumptions. I’ve never experienced this phenomenon, either in cultivation, or in the wild.” I think this reveals the themogenesis of snowdrops as an urban legend.

    • I said in my article that I concluded that the statements that snowdrops are thermogenic were “hearsay” with “no scientific evidence backing them up”, which agrees completely with Aaron Davis. However, I can’t agree with your explanation either because the area in my photo was completely covered with many feet of snow for weeks before the snowdrops emerged—no shielding occurred. There were also lots of other living plants under the snow and only the snowdrops broke through. I don’t pretend that this is scientific, but I still think something is going on.

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