HAVE YOU EVER grown a carnivorous plant—a Venus flytrap or sundew or pitcher plant, perhaps? I bet even a lot of keen gardeners haven’t. Today’s guest is going to encourage us to change that and maybe, as a start, adopt one that you can cultivate on your windowsill even.
All in time for World Carnivorous Plant Day on Wednesday, May 4th, we’re also going to learn about the plight of carnivorous plants in the wild, where they’re disproportionately endangered.
Kenny Coogan is a board member and education director for the International Carnivorous Plant Society (which also has a popular group on Facebook). Kenny’s also author of the recent book “Florida’s Carnivorous Plants,” and he operates a carnivorous plant nursery there. (Photo of windowsill garden of carnivorous plants, above, from International Carnivorous Plant Society website.)
Plus: Enter to win Kenny’s book “Florida’s Carnivorous Plants ” by commenting in the box near the bottom of the page. (To purchase a copy at 30 percent off, use coupon code FLCP30 for 30% through June 1 at this link.)
Read along as you listen to the May 2, 2022 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify or Stitcher (and browse my archive of podcasts here).
carnivorous plants to grow at home, with kenny coogan
Margaret Roach: How are all your hungry little plants down there, Kenny [laughter]?
Kenny Coogan: They’re doing well.
Kenny: They’re eating often.
Margaret: Yes. Good, good. Well fed. So I think you used to live up north, Kenny, and even founded maybe a carnivorous plant club somewhere in New York State, and then moved to Florida. And I keep wondering, is it a coincidence that you move to the state that has dozens of native species of carnivorous plants—I think more than any in the U.S, or [laughter]–
Kenny: Yeah, that’s a good point, but I did not move for that reason. I mostly moved for the weather and job opportunities.
Margaret: But it was serendipity.
Kenny: Exactly. And then I said, “Oh, it’s even easier to grow carnivorous plants down here.”
Margaret: I think I’ve read it has, as I said, I think the most… Does it have the most species in the country or something? I mean it’s quite a diversity in Florida.
Kenny: Yeah. We have over 30 species of carnivorous plants.
Margaret: Wow. So we’ll talk more about that. And before we dig into the plants, Wednesday, May 4th, is World Carnivorous Plant Day. So tell us a little bit about why the celebration is taking place, and what it is.
Kenny: Sure. This is the second annual World Carnivorous Plant Day. It was brought to our attention by a member in Poland that we should offer a day where everyone can celebrate carnivorous plants. A lot of times, when I do presentations, I’ll ask the audience to name a carnivorous plant, and they can get the Venus flytrap and maybe they can get a pitcher plant. And then I say, O.K., well, we’ve only got about 998 more to go.
Margaret: Oh, boy [laughter].
Kenny: So yeah, carnivorous plants are found on all six continents. They are microscopic to pretty large. They serve lots of different purposes in the different environments. And unfortunately, many of them… Well, proportionally, they are more endangered than non-carnivorous plants, because they really like pure ecosystems.
And people like growing them. So we thought it would be a great day to have a celebration where we have conservationists, growers, scientists, educators, authors—we all get together, and we can celebrate these wonderful plants.
Margaret: And you get together virtually, literally around the world, don’t you? I mean, it’s kind of-
Kenny: Yeah. So this is the second year. And last year, my idea was every hour on the hour for 24 hours, I would release a video, and most of the videos are between 10 and 20 minutes. And I’m in Florida, so at midnight, my time, I start releasing the Japanese and the Australian videos. And then I just work around the world.
Margaret: That’s great. And they’re on a YouTube channel, and again, we’ll give links to all these good things, how people can learn more and participate and so forth.
So you’ve been a middle-school science teacher, I believe, until recently, right? I mean, that was what you were doing full-time until recently. Yes?
Margaret: Yes. So pretend we’re students [laughter] with about that level of knowledge, because again, even keen gardeners I don’t think really know that much, for the most part—probably nine out of 10, at least, don’t know that much about carnivorous plants. So just tell us, you hinted a little bit about it in your introduction about the event, but tell us the not-too-complicated version of what a carnivorous plant is, versus non-carnivorous. What is it?
Kenny: Yeah. So well, unfortunately, there really isn’t a scientific line of what is carnivorous, what’s non-carnivorous. What usually happens is if a scientist wants to publish something and say that it’s carnivorous, they can kind of work their way into it. But generally speaking, we say that a carnivorous plant has to lure their prey. They have to be able to digest their prey, and they have to be able to benefit from their prey.
So some non-carnivorous plants, they might be able to kill an insect, like if you think of plants that have thorns or digestive enzymes or sap that could be toxic to insects. But we don’t consider them carnivorous, because they might not be benefiting from the death of the animal. So we like to say that carnivorous plants are on the offense, rather than the defense.
Margaret: O.K. Oh, so it’s not just that they have anti-predation sort of either chemistry or physical devices, like those thorns you mentioned. It’s that they benefit, that they enjoy it [laughter]; they feast on it.
Kenny: Yeah. And that’s where the scientists can get a little vague, because how can we say that they benefit from it? I guess we can count how much seeds and offspring they produce, but maybe another scientist has a different definition of how they benefit from eating the organisms.
So right now, we say there’s about a thousand species of carnivorous plants. Just in the past 40 or 50 years, three bromeliads have been classified as carnivorous. But as you can imagine, there’s probably going to be other groups and even more bromeliads that are going to be classified as carnivorous, as there’s more research going on.
Margaret: O.K. So the ones that we can grow… I know you were going to suggest that we can even maybe get to know them—if not in our gardens right away—we can get to know them on a windowsill, in a pod, in a container or something. And probably through your nursery, you probably have people order some, I imagine, or ask you about—or at trade shows that you do, where you do plant sales and so forth—ask you which are my sort of gateway carnivorous plants, which do I…
So where do we begin? Because I mean, they’re fascinating-looking and the intricacy, their structures, they’re very different from a lot of the plants we grow in our gardens. And so I was curious.
Kenny: Sure. So there’s over 20 genera of carnivorous plants, and we can keep lots of them in our windowsills or in our backyard, and they are from all the six continents, except for Antarctica. So chances are that you will be able to find a carnivorous plant that grows in your area or in your house. And unlike non-carnivorous plants, carnivorous plants generally like a lot of light, and all carnivorous plants really need pure water. So that means they need distilled water or rain water.
And if you have a water meter, they need about 50 parts per million or less of total dissolved solid. So in my city, my city water is almost like 400 parts per million. So that’s way too much for a carnivorous plant. And because I have thousands of carnivorous plants, I have six 50-gallon rain barrels that I collect the rainwater, and that’s usually between 0 and about 5 parts per million. So that’s perfect.
Kenny: And then unlike most household plants, carnivorous plants usually want to be more damp, or they want to be even sitting in water. So those are some things to consider. So for a Venus flytrap, which is the most infamous, they need a lot of light. So if you want to try to grow them inside, the easy solution is to give them a growlight that’s 10 or 12 inches above the plant, or even a fluorescent bulb that’s on for about 12 or 14 hours a day, which is usually a sufficient amount of light.
And they want to be sitting in about an eighth- or a quarter-inch of water all the time, because they’re from the Carolinas, they’re from these swampy areas. So you never want to let a Venus flytrap dry out.
Margaret: Right. Now, they’re in the genus… I never know how to pronounce some of these. Dionaea? Is that how you say it? Venus flytraps. [Venus flytrap photo above from International Carnivorous Plant Society website.]
Kenny: Dionaea. So that’s the genus. And then the species name is muscipula, which means mousetrap.
Margaret: Oh, you’re kidding.
Kenny: Yeah [laughter].
Margaret: Oh boy. O.K.
Kenny: And then the governor of North Carolina named it Venus’s or Diane’s mousetrap, but the common name is flytrap, because he saw a fly get trapped. But then recently, we found out that, in the wild, they mostly eat spiders and crawling insects, and not flying insects.
Margaret: Oh. Well, spider trap doesn’t sound quite as good.
Kenny: Yeah [laughter].
Margaret: No, no, no, no. And so they are native… There is a population of these, a large population of these, that are native to our Southeast. Or where are they in nature?
Kenny: Historically, they’re from a 60-kilometer radius from Wilmington, North Carolina. And maybe 40, 50 years ago, there was a lot of poaching, so the population did go down, and maybe in the past five or 10 years, it’s become a federal law to poach them, and you can get a $10,000 fine and years in jail, if you poach them.
The good news is people are not poaching them, because it’s much easier to propagate them through tissue culture. It’s easier and it’s cheaper to propagate hundreds and thousands of them through tissue culture and breeding. So people aren’t wild-collecting them anymore. And another reason why they’re not doing it is because it’s hard to find them in the wild.
And also about 40 years ago, somebody sowed some Venus flytraps in the panhandle of Florida. And that population is still there, but we do not consider them native to Florida, because they were introduced.
Margaret: I see. O.K., so really, it was just in that one area, huh?
Margaret: That’s pretty amazing.
Kenny: Yeah. And I think what’s really amazing is their snap trap, how they can close so quickly. But there is another carnivorous plant that also has a snap trap, and the scientific name is Aldrovanda. The common name is waterwheel, and they’re found throughout the world, but they’re fully aquatic, and they’re eating little microscopic organisms.
Margaret: So who else can go on our… So this is one, the Venus flytrap is one that we’re going to put on our windowsill. It has to be in a saucer or whatever of water. It’s got to have good light, and-
Kenny: Yeah. And usually, a window probably will not provide enough light. So it just needs a little extra supplemental light, and a fluorescent bulb is good enough.
Another group of carnivorous plants that are good for a windowsill are many subtropical and tropical species of sundews, and these look like little octopus. Two species that are really good for a windowsill are Drosera spatulata [above], which has these little spoon leaf shapes for their leaves. And then another one that’s probably advertised more easily or more common is Drosera capensis, which is the Cape sundew of South Africa.
Margaret: Oh, yes.
Kenny: And that one gets maybe 10 or 12 inches long. And both of them eat fruit flies and fungus gnats. And people love to purchase them when I’m selling. I have a wide selection, but when people see that they eat fruit flies and fungus gnats, and they see it—I mean, there’s actually little bugs stuck to the plants—people get really excited about the idea of wiping out all of their banana bug problems.
Margaret: Yeah. I mean, that would be… I mean, for those of us with houseplants, especially if we’re growing them in a potting medium that has peat in it and so forth, and it’s a little moist sometimes, you can get an outbreak of fungus gnats. So huh.
Kenny: So the sundews and then also Mexican butterworts, and their scientific name is Pinguicula—all of those will eat the whitefly and fungus gnats and fruit flies. They’ll eat a lot of them. And even if you have an army of these carnivorous plants, they’re not going to take care of all of your pest problems, but they will help mitigate them a little bit.
Margaret: Huh. Interesting. And light-wise, how’s that…
Kenny: Yeah. The sundews do good with a bright sunny window. They probably do not need supplemental lighting. And then the Mexican Pinguiculas, the butterworts, they’re about the same.
The more light you give carnivorous plants, generally speaking, the brighter they become. So some Mexican butterworts, they’ll go from green to pink and purple, and then the sundews go from green to red. And the more sun, the dewier they get, which attract… They produce more of their digestive enzymes, which attracts even more bugs. So usually, six to eight hours of lighting is sufficient to keep them.
Margaret: So now you said the dewiness, so that sort of glistening aspect—that’s a functional thing, that helps them to do the trapping. Is that the idea?
Kenny: Yep. So the bugs are attracted to it, and then it’s very sticky. Scientists are really interested in it because the stickiness is not soluble in water. So they’re trying to figure out how they can make glue that we can use underwater, based off of the sundews and the butterworts.
Margaret: Oh, interesting, interesting, interesting. I didn’t know that. And they are so intricate-looking. When you look at them closely, they’re just crazy-looking [laughter].
Margaret: And so with these so far, I mean, are those in a saucer of water—what about the rest of the habitat, so to speak?
Kenny: Yeah. The sundews do good with a little saucer of water underneath them. I always keep them damp to wet. Some people have even experimented—if you’re a beginner, I wouldn’t do this—but people have even experimented having the Cape sundew, Drosera capensis, underwater, under 5 inches of water, and they’ll live for a couple of months like that.
Margaret: Huh. And what am I… These probably don’t come, when they come by mail, by mail in a pot or with the saucer, or with the medium or whatever. I mean, what would I need to be ready to receive such plants?
Kenny: Yeah. So for the plants that I’ve mentioned, I would do half peat and half perlite.
Kenny: You could also do all long-fiber sphagnum.
The flytraps may or may not be potted when you order them. The sundews usually are potted, and then there’s a piece of plastic over the soil medium, because you don’t want the plant to be covered in the medium because it’s so sticky. It just grabs hold of anything.
But because most of the sundews have these tiny little roots, most nurseries ship them in their pots.
Margaret: Oh, I see. O.K. So some may come bare-root, so to speak, and some other types may come potted.
Kenny: Yeah. A lot of nurseries also offer like, “Oh, for an extra $4, we’ll send you it in the pot.”
Margaret: But so far, the medium for those would be half peat and perlite, or to use the sphagnum, the longer sphagnum.
Kenny: And then another potential for a windowsill are the Asian pitcher plants, which are the Nepenthes, which are often seen in hanging baskets. And while Nepenthes would probably want a more humid environment, they will adapt to a lower humidity on your windowsill or in a kitchen or in a bathroom.
When growers sell Nepenthes [above], they usually divide them into two groups. There’s the highlanders and the lowlanders. So the Nepenthes species that are from the top of the mountain, they’re called the highlanders. And then the ones that are on sea level are called the lowlanders.
So if your conditions are more like the top of a mountain, which is around 50 to 70 degrees Fahrenheit, pretty humid, pretty bright, indirect light, then maybe a highlander would be good for you. Where in Florida, if your temperatures are more like 80 to 90 during the day and night, really high humidity, high temperatures, then lowlanders would be good choice.
Or if you’re kind of in the middle, you could also look for species or hybrids that are intermediate. So a lot of breeders are breeding plants from the top of the mountain to the ones at the bottom of the mountain. And now, these plants are good for 45 to 90 degrees. They’re good with a range of humidity. They look super-cool. They have different shapes and colors on their pitchers.
Margaret: Huh. So this is the Nepenthes, the Asian ones—the Asian pitchers.
Kenny: Yeah. And-
Margaret: Is Sarracenia the one of our native genus-
Margaret: …of pitcher plants? How do they compare visually, the Nepenthes versus the Sarracenias?
Kenny: The Nepenthes turn into 6- to 15-foot or even longer vines. And then the pitchers, depending on the species, some of them can only be a couple inches. Some of them can be as large as… Some of them can hold a liter of water and digest a rat [laughter].
The Sarracenia, which are the native North American pitcher plants, they can be 3 or 4 inches up to 3-foot high, and these are the tubes that come up from the ground, whereas the Nepenthes are vines.
Margaret: Oh, I see, so very different. Huh. So that’s why a hanging basket, as you said, works. Oh, interesting.
And now, a lot of times, I’m up in the North, obviously, quite a different environment from yours, with the long winter. But in the May to September-October, I take most of my houseplants outside. Now, if I had these types of “houseplants,” could I put them out in maybe not a baking-hot location, but could I put them out… Where would I put them, if I were to let them enjoy the summer outdoors? Or isn’t that a good idea?
Kenny: No, it’s fine. So the Venus flytraps, the Sarracenia and the sundews that I mentioned and the Mexican butterwort, all of them would do good in full summer sun.
Margaret: Oh, O.K. But with that water, with that water beneath them.
Kenny: Yeah. They still want to be sitting in a little bit of water. And then the Asian pitcher plant, the Nepenthes, they want to be grown more like an orchid in bright, indirect sun.
Kenny: So a little shadier.
Margaret: Huh. So those are some of the good ones for sort of getting started indoors, do you think?
Kenny: Yeah. So those are good beginner plants, and they’re good for beginners because they’re easily available, and their conditions are pretty similar to what non-carnivorous houseplant growers are used to.
Margaret: O.K. And we’ll give some resources I think, like your nursery. We both have, for a long time, known California Carnivores, for instance, out on the West Coast, which is a mail-order source as well. So we’ll give that with the transcript, too, if people are interested. I think it’s good to buy from people with expertise with these plants. Not… Do you know what I mean? Because you see all these places, they’re being sold everywhere, but [laughter]-
Kenny: Yeah. So when I’m at the plant sales every weekend, quite a few people will walk by and say, “Oh I already…” Well, first off, they’ll either say, “Oh I kill them.” And then tell them, “Oh, I could probably teach you how to keep them alive.” [Laughter.]
Margaret: Right. Right, right.
Kenny: And soon as I tell them that city water and well water kills them within about a month, then they always say, “Oh yeah, that was my problem.”
Margaret: O.K. So that’s one of the things. So maybe in these last few minutes, any other sort of basic rules on how to care? First, so the water source is really important.
Kenny: Yeah. So they want to have clean water. Usually, they want to be watered more than normal houseplants. And if we’re talking about beginner advice, they do not want to be fertilized.
Margaret: O.K. So right, right.
Kenny: So Miracle-Gro soil that has fertilizer in it. You don’t want to be adding extra nutrients, because where they’re from, generally speaking… There’s over 1,000 species, but generally speaking, they’re from habitats that are moving minerals and contaminants from the soil away from their roots. So they’re just not adapted to be able to withstand high concentrations of chlorine, fluoride, mineral salts.
So another thing is most carnivorous plants would prefer to be grown in a glazed pot or a plastic pot.
Kenny: So the only one that I would really avoid are terracotta pots because they’re too salty.
Margaret: Oh, they’re salty. O.K. The other two that you mentioned also hold water a little, keep moisture in a little bit longer, I think, than terracotta.
Margaret: Well, Kenny Coogan, now, I want to go to the local nursery and see what they have [laughter]. But May 4th, Wednesday, May 4th is International Carnivorous Plant Day, we’ll give more information about that. Thank you.
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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 11th year in March 2020. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the May 2, 2022 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify