Episode 282: the Venus flytrap
Contrary to popular belief, the venus flytrap doesn’t eat many flies in the wild.
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TRANSCRIPT
[0:00] Music.
[0:16] Hello and welcome to On The Ledge, the podcast that puts houseplants where they should be, front and centre.
[0:24] Music.
[0:29] I'm your host Jane Perrone and in this bonus episode of the show I'm bringing you a chapter from my book explaining the mysteries of the Venus flytrap.
[0:46] I don't know if you've seen it, but John Lewis, the British department store, puts out a Christmas ad every year, which for some reason always makes the headlines. And this year it made the headlines because the starring role was played by a Venus flytrap. So I thought that given the number of misconceptions that were thrown up in that ad from the Venus flytrap growing from an acorn sized seed to the Venus flytrap being rather interested in eating the family dog and also having the ability to unwrap Christmas presents that I thought it might be good to bring you the Venus flytrap chapter from Legends of the Leaf Now, this is in celebration of the fact that Legends of the Leaf is now available on Audible, as well as Spotify and lots of other audiobook sellers. This is just one of the 25 chapters in the book, so there's loads more to enjoy if you spend one of your Audible credits or choose to buy this as a one off. You can learn about everything from why preppers love snake plants to the house plant you can eat as tempura.
[2:02] If you visit janeperrone.com and click on books in the top right hand corner, you can go and find all the ways you can get hold of a copy of Legends of the Leaf, either in physical form or as an audio book. All the links are there.
[2:17] Or you can be like new patron Joseph, who became a super fan this week, unlocking extra access to the Legends of the Leaf audiobook in full, as well as my Allotment Keepers Handbook audiobook in full and loads of other benefits. But in the meantime, let's listen to the Dianaea Muscipula chapter.
[2:42] Music.
[2:50] Diana muscipula - the venus flytrap - Drosoraceae.
Imagine the home of the venus flytrap your mind probably conjures up a steamy jungle full of lush vegetation that envelops your every step. In the centre sits Dionea muscipula, the air pulsing with fat flies about to be lured to their doom. Wrong, wrong, wrong. This is a plant that lives on the margins of bogs populated by evergreen shrubs and pine trees. Dionea muscipula's native range is the coastal bogs of North and South Carolina in the US, within a few dozen miles of the port city of Wilmington. Fly traps require unobstructed sunlight and plenty of moisture.
[3:46] They are used to a shallow water table caused by an impenetrable layer of organic matter known as a hard pan that prevents drainage, leaving the ground constantly moist.
[3:58] The soil is a mix of peat and sand, acidic and nutrient poor, and flytraps are often found growing in hollows or on sphagnum moss.
[4:08] Their other requirement is fire. Flytraps do not grow under dense vegetation. If they begin to be swamped by leaf litter and overhanging plants which block their light, they will decline. Naturally occurring wildfires burn off this competing vegetation. While fires often scorch away the top growth of the flytraps, this does not kill the plant, which regrows from a rhizome, a thickened stem that stores water and nutrients, and escapes damage as it grows well below the soil's surface. Scientists have found fly traps fare best in places where wildfires occur every few years fly trap habitats are biodiversity hotspots home to other rare species such as the snake mouth orchid pegonia ophoglossoidis and fellow carnivores the north american pitcher plants saracenia flavor and saracenia purpurea the thread-leaved sundew drosera filiformis and and the round-leaf sundew, Drosera rotundifolia.
[5:13] The flytrap is teetering on the edge of extinction in the wild. It is listed as vulnerable on the International Union for Conservation of Nature's red list of threatened species. Current estimates put the number of flytraps left in the wild at less than 500,000, just 2% of their estimated original population size.
[5:37] There are multiple threats. encroachment by building development, agriculture and logging, wetland drainage and continued poaching.
[5:47] It is now a felony to poach Venus flytraps in North Carolina, but it is a difficult crime to detect as thousands of plants can be taken from the ground in a short time. As human development closes in, there's another issue. Humans suppress wildfires to protect their property, which allows more vegetation to shade out the flytraps. Wildfires come less often, but are more severe, killing off flytrap rhizomes for good. Rising sea levels due to climate change pose a further risk as the landscapes fly traps inhabit are often only 2-4 metres above sea level, Let's smash another fly trap myth now Fly traps don't catch many flies in the wild The majority of creatures caught are ground dwellers Ants and spiders each account for a third of their diet it, while grasshoppers, beetles, springtails, mites, millipedes and centipedes make up most of the rest, plus the occasional flatworm when traps become submerged during flooding. Depending on which scientific study you consult, flies make up just 1-18% of the flytrap's haul. Trapped creatures dissolve in a nutrient-rich liquid the plant can absorb to make up for the the poverty of its soil. There is, however, one creature that turns the tables on the flytrap.
[7:13] The Venus flytrap cutworm moth, whose cappuccino-coloured, faintly striped caterpillar feeds exclusively on Dionea muscipula. The flytrap's white flowers are held on stems 15 to 35 centimetres above the traps, seemingly to stop their pollinators from becoming dinner too. There is scant research into their pollination habits, but sweat bees, longhorn beetles and checkered beetles seem to be the main candidates. dates. Dionea is one of two species that employ snap traps formed from modified leaves. The other plant with this adaptation, the waterwheel plant, Aldrovanda vesiculosa, is an aquatic plant with a wider geographic range, but its two to four millimeter long traps are harder to observe. Evolution and Mechanism of the Venus Flytrap
[8:03] The mechanism of the Dionea muscipulus trap itself is not fully understood, but scientists agree that that it evolved out of its close relative, the sundew. The tentacles of the sundew have evolved into the trigger hairs that arm the inside surface of each clamshell-shaped modified leaf of a flytrap, usually a trio in a triangle shape. The rows of teeth, or cilia, that enmesh as the trap closes seem to have evolved from sundew tentacles too. Scientists are still delving into how flytraps attract their prey. What seems clear is that they release a cocktail of at least 20 chemicals that mimic the scent of fruit and flowers. Some studies suggest that fly traps display a pattern of ultraviolet light absorption that helps prey home in on the traps. How does the trap know the difference between a potential meal and a gust of wind? Any one of the trigger hairs must be stimulated twice or more in a period of around 20 seconds for the trap to snap shut. The two sides of the leaf snap together in a third of a second, but the trap only seals tight shut if the hairs continue to be triggered by struggling prey.
[9:20] Once this happens, digestive glands lining the inside begin to release an acidic liquid full of proteins and enzymes to break down the meal. Each hair trigger sends an electrical signal to the whole trap, causing it to release stored energy and rapidly switch from its open concave shape to a convex shape, like an umbrella blowing inside out. Recent research has shown that these signals also produce magnetic fields, one of the first times this has been detected in the plant kingdom.
[9:56] How did the indigenous people who lived alongside the flytraps understand and interact with these plants? Available information is scant. Unsurprising for a culture that has been effectively erased from the landscape in the last 300 years. The Cherokee people who lived in what is now called North and South Carolina had their land taken by European settlers in the 1700s, lost their lives to introduce diseases and were forcibly removed to so-called Indian Territory in Oklahoma. The Cherokee name for the flytrap is Uquilor, but this term was used to refer both to Dianaea muscipula and Saracenia purpurea, the North American pitcher plant, as well as other species. Cherokee Nation member and ethnobotanist Dr. Clint Carroll told me, As with most Cherokee words, the name describes physical properties of the plant, so this name has been used for numerous different species that have similar appearances or do similar things in their environment from the perspective of Cherokee speakers. American ethnographer James Mooney, writing in 1891, reported that Cherokee fishermen chewed a piece of what he called uquilor and spit it onto the bait and hook to imbue them with the seductive power of the plant.
[11:19] This corresponds with the words of J.T. Garrett, a member of the Eastern Band of the Cherokee from North Carolina, who notes in his book, The Cherokee Herbal, Native Plant Medicine from the Four Directions, that the root of the plant was chewed out and spit on the worm or bait. Garrett writes that the flytrap is classed as a special medicine that was just not talked about out to anyone.
[11:43] Indigenous plant knowledge was, and still is, prized and therefore not dispensed lightly. As Dr. Carroll puts it, the adage, knowledge is power, has literal meaning for Cherokees. The man who first brought the Venus flytrap to world attention was Scottish-born politician and landowner Arthur Dobbs, who lived in Carrickfergus on the island of Ireland.
[12:08] Dobbs set out for the US in 1754, after Britain appointed him governor. In 1759, he wrote to British naturalist Peter Collinson, We have a kind of catch-fly sensitive, which closes upon anything that touches it. I will try to save the seed here. The Venus flytrap first made landfall in Britain in July 1768, in a shipment of moss-wrapped plants imported by William Young, an American plant collector. This prompted feverish excitement from British naturalists, hoping to get their hands on a specimen. Dobbs' friend Collinson wrote, I am ready to burst with desire for root, seed or specimen of the waggish tippitywitchet.
[12:54] Writers, specifically male writers, have expended a huge amount of energy exploring whether tippitywitchet, a word ascribed various meanings including a twitching fur stole, a cassava squeezer, and a trap for catching rabbits, was a euphemism for the female sex organs. The flytrap's glistening red interior, fringed with tooth-like hairs, does certainly conjure up the myth of the vagina dentata, as Freud dubbed it. The tale told across many cultures that cautioned men of the perils of sex with unknown women. I suspect this tells us more about 18th century sexual mores than it does about the flytrap. But it does point to one aspect of the plant's pull on our consciousness. Dionea muscipula waggishly slipped the bounds of classification. Is it male or female? Flora or fauna? Amphibian or land dweller? Intelligent or mindless?
[13:59] In 1773, British naturalist John Ellis gave the flytrap the scientific name Dianaea muscipula. Ellis claimed that this was due to the beautiful appearance of its milk-white flowers and the elegance of its leaves. But the name has caused much confusion, because Dione refers to several different people in ancient mythology, including the mother of the Roman goddess of love and sex, Venus, Venus, and the mother of the Greek equivalent, Aphrodite, or Aphrodite herself. Added to that, muscipula does not mean flytrap in Latin, but mousetrap, and yet somehow the name Venus flytrap has persisted.
[14:41] Names also proved a problem for Carl Linnaeus, the Swedish botanist who came up with the system of naming plants and animals that scientists still use today, when he was sent a specimen of the plant. It was dead on arrival, so he could not see the plant in action, but he still deemed that the mere idea of a plant that ate animals was against the order of nature as willed by God, deciding that the plant must be merely allowing insects shelter from rain. Charles Darwin was a flytrap fan, calling it one of the most wonderful plants in the world, although he was frustrated that he could not keep one alive for long. Darwin's experiments showed that fly traps were indeed carnivorous and resulted in his book Insectivorous Plants, published in 1897. Despite its tiny size and inability to catch anything larger than a tiny lizard, artists have consistently portrayed fly traps as man-eaters.
[15:43] In 1880, Sir Arthur Conan Doyle published The American's Tale, a story about a man eaten by a giant fly trap in Arizona. The trope was reworked in the 20th century with John Wyndham's 1951 book The Day of the Triffids and Audrey 2 in the 1960 film Little Shop of Horrors. And yet, there are signs that Dionea muscipula may be able to help us, not harm us. Early research into genetically modifying fly traps using a certain type of soil bacteria has shown this can boost their existing capacity to produce phytochemicals with the power to tackle human antibiotic-resistant bacteria. If we can protect these plants in their wild habitat, who knows what other secrets they may yet yield.
[16:35] Care Guide. Provide as much sunlight as you can muster. It is entirely possible to grow flytraps in an unheated greenhouse in the UK's temperate climate. They die back over winter, resprouting from their rhizomes come spring. Many dianeia experts believe the plants require this period of dormancy to thrive, during which they experience shorter daylight hours and lower temperatures. But the advent of cheap full-spectrum grow lights used 12 to 14 hours a day have allowed some growers to experiment successfully with growing plants indoors all year round without a dormant period. Temperature. If you are growing them indoors without grow lights, give fly traps a cooler resting period over winter, placing them in a brightly lit, Unheated room, porch or similar where temperatures drop to around 10 degrees centigrade, 50 Fahrenheit, Water Place pots in a tray of water 2 centimetres or so deep from spring to autumn and keep them moist but not wet in winter. The safest option is to use rainwater or distilled water. Regular bottled water and water from a home filtration system aren't suitable. But if you have a reverse osmosis RO system installed, or can source RO water from an aquarium shop, this is fine to use.
[18:04] Humidity. Venus fire traps love humidity. Pests and diseases. The two main possibilities are red spider mites and aphids. Substrate. It is still widely assumed that flytraps require a peat-based substrate to thrive, and half-peat, half-sand is often recommended. Given peat's status as a non-renewable resource, growers have been working hard to come up with a peat-free substrate for flytraps. Ready-made mixes are available from UK growers Floralive and Wax Wicked Plants, while other growers grow in sphagnum moss or a mixture of fine milled bark, lime-free horticultural grit and perlite to a ratio of 2 to 1 to 1. A 2cm deep mulch of sand is recommended by some growers. Propagation Don't buy the commonly available grow-your-own-fly-trap seed kits. They usually fail as the seeds need to be sown fresh. Fresh offsets can be carefully prized away from the parent plant and potted up separately or cut the rhizome into pieces in spring, making sure each section has some leaves and roots and pot up separately. Leaf cuttings using a whole leaf pulled away from the plant and laid on damp substrate will grow into new plants, but this method is slow.
[19:31] Flowering stems can also be propagated in this way. Help to speed along the process, by encasing the tray or pot in a clear plastic bag to ensure steady air humidity. Feeding. Some growers advise feeding extra food for fly traps, rehydrated freeze-dried bloodworms available from aquarium shops for instance, but this is not essential. Other maintenance tasks. Growers disagree over whether flowers should be removed to nudge the plant to putting more resources into producing more traps or left.
[20:08] Danger signs. Traps rapidly dying back in summer can be caused by a lack of moisture or use of tap water. Toxicity. No known toxicity to pets or humans. Display. Fly traps do best in glazed pottery or plastic containers. Cultivars. Flytrap breeders have had a field day coming up with all kinds of variations on the flytrap theme, from cultivars 'Akai Ryu' and 'Bohemian Garnet', which are a dramatic dark red all over, and the extra-large 'La Grosse à Guigui' and 'B52', to oddities such as 'Crispy Sun', which has traps with fused teeth. Also try. There are many fascinating carnivorous plants available for indoor cultivation. Sundews and Butterworts act like living flypaper, while the tropical pitcher plant species in the genus Nepenthes are also widely available and relatively easy to grow indoors.
[21:15] Music.
[21:22] So that's the Venus flytrap. I hope you enjoyed that chapter. And if you're interested in the research papers and books that helped me write this chapter and the rest of Legends of the Leaf, head over to janeperrone.com/legendsresearch, where you can see all of that information in one place. And if you liked what you heard, there are another 24 chapters of of the book to enjoy via your audiobook app of choice including audible and spotify all of the links are at janeperrone.com/legends-of-the-leaf.
[22:05] And now we have time for a short question of the week - this one came from Ana who is in Croatia and wanted to know about online education about houseplants. So courses, masterclasses about houseplants, where can you learn more? Well, of course, I'd say the first place to learn is on the ledge. You've got more than 200 episodes here, which covers a lot of ground. But I understand if you want to learn in a more systematic way, that might be something you are looking around for. There aren't that many options, but let me run through the ones that I know about.
[22:43] UCLA Extension in California runs an indoor plants care and maintenance course led by leslie hallock who is a guest of the show and an expert horticulturist so you can do this course online and it covers plant choices watering pruning disease naming and identifying plants i will put put links in the show notes to all of these. There is a class starting on January the 9th and it runs I think for 11 weeks. So that is an option if you want to expand your skills, certainly that is a good option. It's online so you can do it from anywhere in the world and there are various different elements to the course. So that's an interesting one and UCLA also runs a general botany for gardeners course as well. So those are a couple of options which might be worth knowing about.
[23:40] You know, you're talking about several hundred dollars. I think the houseplants course costs about six hundred and seventy dollars. So it's an investment. But with Leslie, you know, you're getting a really good grounding in houseplants and their care next up create academy has an indoor gardening master class with james wong another guest of the show and i've heard people take this course um there are 28 lessons again it's all online and there's a downloadable workbook it takes eight hours to complete so it's shorter than the UCLA course but it is considerably cheaper so i think at the minute it's 59 pounds 25p and you could give that to somebody as a gift i think it's having got a christmas discount on at the minute and normally it's 79 pounds so it gives you a chance to learn about houseplants and their habitats with the inimitable james wong and it also has lots of hands-on projects, the kind of thing that James Wong loves to do, like kokedama, paludariums, aquascaping, terrariums, and so on. So I think if you're into that style of houseplants, that would be a really good course to study. If you want a general grounding in horticulture with a houseplant element, the RHS Level 2 course is something to have a look at. I would say that it has been been updated in the last year and so it's a bit different from when I took it and I think the houseplant element the the sort of indoor horticulture element has changed too this is a course that's equivalent to a GCSE - so a GCSE if you're not from the UK is a qualification you take when you're 16 and that's the kind of level of academic study we're talking about here there's a lot to learn you don't have to take the exams you could just study the course with a variety of of online providers, but obviously, if you want to get the qualification at the end of it, you have to do the exams. And it covers everything from botany and identifying plants to growing vegetables so it's way wider than houseplants but definitely worth a look if you're looking to get an RHS approved qualification there is also a houseplant 101 page on the Royal Horticultural Society website which has short videos I think there are about nine of them and they're only two or three minutes long about houseplants and how how to care for them. If you're looking for something very basic that covers the foundations, then that would be a good place to start too.
[26:26] The only other course I know that's directly relevant to Ana's question is a course that's run by the botanist Scott Zona. I don't know if he's offering this course at the moment. It's called The Botany of Houseplants. It's a four session webinar which runs once a week over a month long period. And it's very reasonable. I think the last time it ran, it was $25 for the four one hour sessions, which is extremely reasonable. I'm not sure if Scott is offering the course in the immediate future, but I'm sure if enough of you were interested, then he would certainly, uh, be doing more of those in 2024. So again, I'll put as much info into the show notes as I can, but yeah, there isn't really, one particular course that I would recommend it depends what you're looking to get out of it and there may be courses in other countries that I don't know about, but do fill me in if you know of any other houseplant courses that are worth including in this roundup. Thanks for your question, Ana, and I hope that helps a little. And maybe there's a houseplant course that doesn't exist that you would like to take. Tell me about what it would be and maybe that's something we can look at for 2024.
[27:44] I'd also love to know if people would be interested in a Zoom workshop workshop about how to read a scientific paper. Would that be something that would be interesting to you? If I can get enough people interested I'd love to run this just an hour-long Zoom workshop about how to demystify the world of academic papers if you want to get into that kind of stuff. Shoot me an email or a message if you're interested. If I get enough interest I will certainly run that sometime in spring 2024. One other little soupçon of housekeeping. thank you to city slash county gardener for your delightful review of on the ledge on apple podcasts in the us i appreciate you and thanks to everyone who supported me in the last year from buying my book or houseplant gardener in a box becoming a patron making a one-off donation on ko-fi telling a friend about the show or simply just listening it all makes a difference in nearly seven years this show has built into a wonderful community that i'm just super proud to be a part of so give yourself a pat on the back and let's look forward to loads more planty fun and info in 2024 have a fabulous festive season whatever you're up to, and i'll see you on the other side - bye!
[29:08] Music.
[29:13] The music you heard in this episode was Roll Jordan Roll by The Joy Drops, The Road We Used to Travel When We Were Young by Komiku and Namaste by Jason Shaw. All Tracks are licenced under Creative Commons. Visit the show notes for details.
[30:06] Music.
Hear an extract from Legends of the Leaf profiling the venus flytrap, and a Q&A about houseplant courses.
Like what you hear? Order your copy of Legends of the Leaf here.
An illustration of the venus flytrap from Legends of the Leaf. Illustration by Helen Entwisle.
Chapters
0:02:50 Venus flytrap book extract starts
0:05:13 Threats to the Venus flytrap in the wild
0:08:03 Evolution and mechanism of the venus flytrap
0:09:56 Indigenous people's relationship with the flytrap
0:11:49 Arthur Dobbs and the introduction of the venus flytrap
0:16:35 Venus flytrap care guide
0:22:05 Q&A: courses for houseplant enthusiasts
0:29:13 Music credits
Notes to read as you listen…
If you haven’t seen the John Lewis Christmas advertisement that inspired this episode, view it here.
You can check out my Insta reel about the ad here.
If you like what you hear, you can buy a copy of Legends of the Leaf in print form, audiobook or ebook. Click here for all the links you need.
You can also join the Superfan tier on my Patreon and get access to the Legends of the Leaf audiobook and so much more! Find out more.
If you want to check out the research papers and books that informed Legends of the Leaf, visit janeperrone.com/legendsresearch.
You can find more episodes on carnivorous plants here.
Question of the week
Ana got in touch to ask about courses that teach you more about houseplants. I suggested the following:
Leslie Halleck’s indoor plants course for the UCLA Extension. There’s also a Botany for Gardeners course.
James Wong’s Create Academy Indoor Gardening Masterclass.
Several providers in the UK offer the Royal Horticultural Society Level 2 course - more info and a list of providers here. The RHS’s Houseplant 101 page is also worth a look.
Botanist Dr Scott Zona has offered houseplant botany classes on Zoom.
Order your copy now!
Houseplant Gardener in a Box is now out worldwide!
Grow happy, healthy houseplants with the help of these simple, illustrated cards. The 60 informative cards, illustrated by artist Cody Bond, and 32-page book packaged in a giftable box.
I answer hundreds of questions, including: What sort of plants love a bathroom? How can you bring an orchid back into flower? What needs regular watering, and what doesn’t mind if you forget? What can you put on a sunny windowsill, and what will send foliage tumbling attractively from a shelf? Drawing on years of experience and research, her cards provide sensible, practical, and inspiring advice. The accompanying book will guide you through the process of selecting plants, and Cody Bond’s beautiful illustrations will inspire you along the way. Order your copy now from all good bookstores (and lots of plant shops too!)
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CREDITS
This week's show featured the tracks Roll Jordan Roll by the Joy Drops, The Road We Use To Travel When We Were Kids by Komiku and Namaste by Jason Shaw.