In this edition of Gardening Unplugged, Dr. Patrick McMillan demonstrates some of the native carnivorous plants that you can grow at home. Many of these unique plants are actually native to the Southeast US and, in the case of the Venus flytrap, native to our own state of North Carolina. Gardening Unplugged is an ongoing series of informal gardenside chats conducted during our Open Nursery and Garden Days.
I have spent most of my career… 20 years I was a professor in botany and I spent 15 years on PBS also doing a TV show called Expeditions with Patrick McMillan where I went all over creation looking at things like carnivorous plants and bringing really what I what I thought were really cool stories, at least to people, engaging things about elements of the world that we don't usually think about. That’s what I always love to sort of tickle people’s minds with and carnivorous plants are a very popular topic. It’s one of the most popular groups of plants because children love thinking that a plant eats an insect right. That's pretty amazing that you have something that's carnivorous.
Okay, well to burst the bubble, thing number one - they don't actually eat insects. They don't actually eat anything other than the same thing most plants that are green eat, which is light. So, when we say eat, we're usually talking about where they're getting their energy from, that's carbohydrates for a plant. So, plants are photosynthetic means that they get their, if they are photosynthetic and not parasites, then they're getting their energy from the Sun. So what are they really getting out of the insects or other things that they catch? Because these don't just catch insects. In some cases they catch larger things and smaller things than insects but what they're really getting is their nutrients. They’re getting vitamins. They’re getting nitrogen particularly out of the insects and that's mostly because of the habitat that they grow in.
Venus Flytrap (Dionea) - The Most Amazing Plant on Earth
So does everybody know… everybody here knows about Venus fly traps right? So I brought you guys some Venus fly traps, and we have some to ruin right here. So, if you want to hold one, please feel free. Would you like to hold the pot? Okay awesome. So, the Venus flytrap Darwin called this the most amazing plant on Earth. You can actually see evidence that it does actually capture mosquitoes because there's a mosquito dead in that one. That is just the exoskeleton of the mosquito. but the Venus fly trap, most people on Earth don't know where you find Venus fly traps. So, who knows where Venus fly traps grow naturally? North Carolina. Yeah Wilmington. You guys are so smart. Like when I used to do a bunch of school groups, I always had somebody who they were right, they were always right. But they you know somebody say Africa or South America or the jungle and no it's North Carolina and South Carolina only just the Southeastern corner of the state and of North Carolina northeastern South Carolina. But I always had some student that would always say Walmart.
They're right, they're correct, they do grow in Walmarts. But they are one of the most poached species of plants on Earth too because folks tend to, down in the southeastern part of the state, not really all their fault because you know the local folks in the southeastern part of the state have a hard time making a living, at least before a lot of the development happened. So, we're sort of, I don't know how I feel about that really, they're trying to make a dollar but shouldn't dig them out of the wild. They’re actually protected by law now and you can face a fine or worse for approaching them out of the wild. But Venus fly traps are a great example that everybody knows about carnivorous plants. So carnivorous plants, to be carnivorous, they have to lure. Means they have to have something to attract their prey. Okay, they have to trap their prey. They have to trap their prey, capture it, and then they have to digest it. Venus flytrap does all of those things. The red coloration on the insides of the trap that glistens is thought to be what lures insects in. It's simply [that] the color red attracts some insects and then the glistening indicates oh maybe there's some good nectar there. So, they might go in and visit. The fly trap closes and when it closes it doesn't want to close on something it's not going to get food out of. So, what could fall into their fly trap that we wouldn't want to close on? Rain, yeah. What good is that going to do? It's water, you got that in the soil, right. You don't want to close on a pine needle. You don't want to close on those things you want to make sure it's alive. So, this is so intricate that each side of the Venus fly trap has between three and six little trigger hairs. That's one that has six on that one right there. Actually, you can see three and three but usually they're just one, two, and three - like this one. And those little trigger hairs are attached to an enlarged cell. And what happens if you touch one trigger here like I just did, nothing happens, right. But if I touch one trigger hair twice in rapid succession or touch more than one it closes. And that one's slow to close because it's the second time that trap is closed. The first time they close really fast, the second time they close really slow, so slow. So, all these are slow ones. So, you want to try yours? Here, I’ll hold it, you can try it. Just kind of drag that across. You can see really well those three hairs, yeah. Yeah, a little faster. Before we close this one let's look at it. Most people think that the Venus fly trap is closing around a hinge. It is not. What it's doing is changing shape. And you can see how, you see how the inside of that leaf is sort of bowed outward?
Sundews (Drosera) - A Slow Motion Venus Flytrap
Now I'll show you a few others. This is a two-in-one here. This one has a sundew in there and sundews are kind of like slow motion Venus fly traps. You'll notice that a lot of these leaves the leaf is normally out straight but a lot of them are curling inward. So the way these work is each leaf has, and these are both examples of active traps, that each leaf has these little hairs on the leaf trichomes and each trichome has a little bead of glistening bead on it that's sticky like fly paper. And little insects will be drawn in there just like they are it's red and it's glistening. They get drawn in there and they get stuck in the goo on the sundew and the sundew slowly curls that leaf in to push the insect against the surface of the leaf where the amylase, esterase, and proteases is secreted that gets into the insect and gets at what's important for it. So obviously that doesn't catch big things. No scent or anything, it's simply the color that well in some there are. And we're going to look at that in just a second. Not active press which you might think, oh well they're not as cool because they don't have as good a story, they don't move around, they don't move at all, but pitcher plants actually to me are the most fascinating of all of them. Not only are they weird looking, but they have really interesting traps.
Pitcher Plants (Sarracenia)
So, this is the most widespread pitcher plant. You find this from Canada way north in Canada all the way down to Florida and at least the group the purple pitcher plant group and this is the least intricate of all the traps. Basically, what this guy does is he puts out pitchers of water, he secretes into the water the amylase protease, and then draws in the insects by producing nectar right along the lip and along the suture of the leaf. Now a pitcher plant leaf is kind of interesting because i can illustrate it with this lycoris right here, really what we have in a pitcher plant leaf is a lot of people think that's a flower it's not the flower it's a leaf and the leaf has simply been rolled like this and sutured along the margin to produce the pitcher okay so the abaxial, the bottom side of the leaf, is the side that is exposed. Now if you had the other side exposed, it would be a problem. Does anybody remember basic biology to know why? Yeah, it breathes from the bottom. Yes, it has the stomates along the backs of the underside of the leaf, not the upper side, which is why everything that rolls this way throws it that way instead of the other way around. So that's how they create the pitcher. With the purple pitcher plant, that nectar simply comes up to the edge and we'll look at it on the yellow picture planks a little more sexy than the pitcher plant but that nectar is all along here when the petra first opens up just like in the purple pitcher plant and then it's right here and it's also right here and if you feel right there on the back of that you're welcome to feel it if you want to its sticky okay yeah it's really sticky okay now don't lick your finger, I’ll tell you why in a minute. But the nectar draws in things. And because it produces nectar all the way down the suture here, a lot of times the first thing that all pitcher plants collect are ants. You think about throwing a candy down on the ground right when it comes to an ants in a minute and then you know when that first girl ant comes up and she finds the nectar she lays a pheromone trail back over to the mound and it tells all the rest of the ants to come get it. So, they collect nectar, collect nectar, collect nectar, collect, collect, collect, collect. They get up to the top and down she goes and all of the assistant's followers right down into the trap. And the way the trap works is it's very slick on a purple pitcher plant… on a, I mean on a yellow pitcher plant. On a purple pitcher plant, it's got hairs that point downward that make it hard to crawl up against the hairs so it's easier to slide down but when you get inside, down in the middle, in the bottom towards the bottom of the pitcher, there's little felt like hairs. And really, it’s almost like felt that points downwards so that when something gets down in it, it literally cannot push back out because there's thousands of little hairs pushing down against it to keep it where it is. So, once you've done that, produce nectar here for a few days in the spring, you stop because nectar is physiologically expensive. These things grow in poor habitats. You don't want to waste energy doing that so what they do is they use the dead decomposing body of the ants as bait or whatever they've caught as bait because then flies, right yellow jackets, which love to eat carrion, all come to try and eat that and when they get into the pitcher, they're done for two to get caught right. So, it's cool later in the season after these have been out for a while to cut one open and show everybody what's on the inside because it's amazing to see what they have consumed. And in the case of each species of pitcher plant specializes in catching different things. The yellow pitcher plant specializes in clumsy fliers. So, things like beetles that aren't really great at getting around with dexterity. And also, things like larger bees and wasps that might come in and moths and things that aren't good flyers. And what happens is they have this usually red spot right here that corresponds to a basketball goal, the sweet spot that's outlined with the little square. When they come flying, they see that red and they fly - oh I’m going to get this - boom they hit the sweet spot and it goes right in the basket. And that's how they'll find beetles a lot of times in a purple pitcher plant. Actually, every time I did this with my college classes, we would cut them open in the early fall semester and we almost always found a dead lizard, a dead frog, and sometimes a dead mouse in there. So, it's anything that gets attracted to what's in there. If they get in far enough and if they're small enough to fit in the pitcher, they're done for.
The Asian pitcher plants are even more interesting. They can have… the Nepenthes rajah has really great big pitchers not derived from leaves, actually derived from an inflated tendril. It's a little totally unrelated but they're so big that even small monkeys can sometimes get in and drown, and arboreal rats. That's kind of interesting. All right so this one is kind of the coolest of all of them to me. This is the white topped pitcher plant. And if that one specialized in clumsy flyers, what do you think the attractant here is? Well, it gets ants, and it produces nectar but what do you think this is mostly trying to attract with the white? What pollinates white tubular flowers? Moths? You know, moths, yeah. And so the white reflects ambient light at night the same way here when you turn on a light on your porch and what happens? The clumsy flying moths come up, they fly to the brilliant white, they hit the sweet spot two points right, you get three points for a butterfly and this one gets three points a lot. Because just like the yellow pitcher plant, and like really now we know all pitcher plants, there's a second way that they capture insects. The nectar that they have, which is why I said don't lick your finger afterwards, the nectar contains a chemical called conine okay that's an alkaloid. Anything that ends in INE like caffeine, that we drink right, cocaine right, those are all alkaloids they all have some impact on human beings metabolically or otherwise. Many are poisons and so with the case of the white top pitcher plant and the yellow pitcher plant all of them produce conine. In the case of the white top butterflies like Buckeye butterflies, which actually filmed this from my show, will come up and they'll start nectaring from this because that nectar is nectar; it's sweet, but it's laced with poison. And only two things on this planet produce conine, poison hemlock that's the poison that Socrates drank when he had the choice commit suicide or stop teaching people to think or decided to kill himself. And all that glistening on this is full of that conine, that in insects, causes a narcoleptic response so that when they're sipping on it they get groggy. If you watch the video, we posted it on our website not too long ago in a piece I did on carnivorous plants. They get groggy and pretty soon they fall in, pass out, and they're in there far enough down when they come too, they can't get back. Another interesting thing is that there's always something smarter than the trap so there are species of mosquitoes that only breed inside the water of purple pitcher plants. There's a species of many species but a species of moth, not moth but wasp called Isodontia philadelphica. It is so smart, they also get in your hose pipes at home the same species, Isodontia, they go down in the tube and they build a layer of sticks and straw in there and then they lay their eggs there, so they don't get eaten by the pitcher plant. The babies have a slimy coat on the maggot that keeps them from being dissolved while they're down in the pitcher and they feed on the decomposing bodies of all the insects that the pitcher plant has caught so that Mama wasp doesn't have to do any work. And then when they get ready to come out, they can't get out the top any more than anything else can. What do they do? They chew a hole through the side, and they drop out as a little maggot. They form a chrysalis and then they come out and they pop out of their… not a chrysalis, but they come out of their exoskeleton. They become an adult Isodontia philadelphica and they go off looking for another tunnel.
Q: I was wondering why I had some holes…
A: That’s what it is. They're all pitcher plant wasps, Isodontia philadelphica. Isn't that crazy? So, they're really amazing things. They're very simple to grow. You can combine lots of other cool bog plants like the grass pink Orchid. So, the way that I’ll show you how to… the easiest way to grow these is in a pot. It's the most successful way you'll grow them. Way better in a pot than you'll ever grow them in an in-ground bog like this. The thing about a pot is you can get these for just like next to nothing at Lowe's or Home Depot and you don't want a pot that has a hole in the bottom. You want one plastic that you can drill holes about four or five inches below the top of the pot. You're going to take peat moss and perlite, or peat moss and sand and you can use up to one half peat moss, one half up to one half perlite, one half sand but you really can use any amount of sand and peat moss or sand and perlite that you want just not to keep it from being all peat moss. You can just use a little bit, it still works. The peat moss you need to mix in a bucket of water beforehand because it's really difficult to get it to uptake moisture. So, what I do is put a drop of Dawn dishwashing detergent in there for a surfactant so that it takes up the water quicker and just a drop won't hurt your pitcher plants. Put a whole bunch in there, it's too much sulfides, you're going to ruin your pitcher plants, don't do that. But you just are phosphate, you don't want to do that. So and then just work the peat moss to get it to soak it up throw it in your pot keep doing that until your pot is full of peat moss and perlite and then you're Pat it down a little bit you're ready to plant okay the holes keep the moisture in the in the pot keep the water level right there okay so you don't have to have as deep a pot as this you can use a pot that's only this steep you know and still accomplish the same thing but when you use a little deeper pot you have a larger reservoir of wet water down in there and you don't have to worry about watering it so often to keep the water where it's supposed to be.
Q: Can I over winter in that pot?
A: Absolutely. So, all of our carnivorous plants that you can… you know there are tropical ones like the Asian pitcher plants, but all the plants that we sell are Southeastern native species and they all have to freeze. If they don't get cold, they'll die. So, you can't keep one forever on your windowsill, but you can keep one forever outside just like this and just leave that right outside and let it freeze. These things are hardy all down to like Zone 5 so they don't have a problem with that.
Q: Can you grow them in a pot with a wet saucer?
A: Absolutely. So, if you have a pot with holes in the bottom, you just set it in a deep saucer so that the water level in the saucer is about four or five inches below the top of the pot and that's the key. Now the other thing you have to do is put them in full sun. There’s not a single species that wants to grow in shade and without six hours of light a day you're not going to be successful with any of them. So, they want a hot, sunny place. super easy setup if you do it like this, you don't even get weeds because there's no nutrients so the weeds may pop up a seed but they're going to die right away because there's nothing to keep them around. and it's just a super low maintenance crazy awesome cool thing that you can have to entertain your kids, your grandkids, and yourself.
Q: If you do this and sit it on concrete or anything is it going to make it too hot in the sun?
A: No, no. Don't get a black pot because the black will collect heat but it's not going to get too hot. they can tolerate 130 degrees.
Q: So, all you need is uh peat moss and perlite no sand?
A: Or peat moss and sand. Anything to just break up the peat moss a little bit is okay, but you don't want something that's going to put nutrients in there and that's why we use clean sand.
Q: Do you have to wash the sand? Is there a certain type of sand you'd be looking for?
A: Yes. So usually, we use river sand and some of the sands are coated.
Q: So not play sand?
A: No, play sand because it's sometimes coated, and the coating might be bad for the plants. so, an easy … get a bag of perlite. You know what that is around here. in South Carolina, river sand was available everywhere, it's not here. so here it's a little more difficult to find lots of river sand for doing stuff like that.
Q: Can you grow them from the seeds from the, you know, when the pitchers for the flowers?
A: Super easy, yes. So, when they… so the flower which we didn't talk about but we should. This is the flower of a pitcher plant, and the petals are right here around the outside and they fall off very quickly and they leave behind this sort of strange capsule, like this one's fallen off. there's the last pedal boom and you have this weird umbrella that's the stigmatic umbrella and down here you have the capsule that's full of seeds. and when that dries out and pops open, the seeds are tiny and they just spread all over in your box and they all come up and if you have one species of pitcher plant that's what you'll have if you have another species of pitcher plant anywhere nearby you're going to get a lot of hybridization because pitcher plants are sluts, they don't care who they breed with. They go everywhere.
Q: That’s a question. You see so many crosses, you know in the various nurseries, how many actual species are there in North Carolina and South Carolina?
A: In North Carolina and South Carolina, including the mountains, there is the mountain purple pitcher plant, the Mountain Sweet pitcher plant - which is federally endangered, the green pitcher plant - at one site in Clay County which is also federally endangered, the yellow pitcher plant, the coastal purple pitcher plant, the hooded pitcher plant - just in two counties in the lower Southeastern coastal plain, and the sweet pitcher plant, Coastal sweet pitcher plant, Sarracenia River, so seven… six species and there's two varieties of purple pitcher plants so seven taxa, I think in North Carolina, I'm not missing any. and lots of hybrids, yeah. And then in South Carolina you pick up in the very south southeastern corner you pick up parrot pitcher plant if one at least historical location and in Florida and panhandle of Florida you pick up white top pitcher plant Gulf Coastal plain you pick up tall picture plant Alabama you pick up the Alabama pitcher plant you pick up the Rosia purple pitcher plant in the Florida Panhandle and I think that's… okay, did I get them all? Alabama, I got, I think that's all the pictures. oh, there's one more variety of rubra which is yeah possibly too.
Q: And what about the Venus fly traps? How many actual species?
A: One pure, so one species in the entire family. There's one species, if you consider it a separate family from Droseraceae. Some people put them in the same family as the sundews but it's a monotypic genus which means one species. in a monotypic family if you recognize the family is distinct as Dionaea, so it's pretty unique yeah.
A: Yeah, yeah, and its hybridization and selecting forms. because like this one, ‘Tarnock’, is found in one bog called Tarnock, Tarnock bog, and it has sterile flowers that have lots and lots of those shields out, sepals coming out, and it has no pedals. but that's a form that was selected by the Atlanta Botanical Garden and called Tarnock after the site, I guess, where they found it. and it's a beautiful one. There are other white tops that have green veins instead of red veins. and yellow pitcher plants come in anything from solid red pitchers to solid yellow pitchers, to dual colored, to copper colored, because there's a lot of variation in the wild.
Q: So, I'm working on setting up a bog at home and I keep reading discrepancies about the peat and perlite mixture. some people say…
A: I've been doing this for 35 years, it does not… you can put a slab of peat in there and they're going to grow, okay. so it doesn't matter how much. you just need some to… you just need some to break it up and the perlite is more expensive.
Q: Okay yeah because they were saying that perlite is alkaline, and it might throw off the pH and I just did a 50/50 mix so I'm like - oh I don't want to re-pot that.
A: You’re fine, you're fine. Any other questions? Yes?
Q: Okay, how high are you going to bring the peat? all the way?
A: All the way, all the way up to here.
Q: And then you're going to put your… the top of the plant will be here so then the roots will be down there, yep and the roots aren't going to grow beyond where the water… down into the water. they grow just above it. So, if we look at the pitcher, of a pitcher plant's roots… so, you can see that there's not that much. They don't have a big tap root or anything. they have these rhizomes on the surface and then all these fibrous roots that come down from that. So, they don't have a huge root mass so you don't need that much space to make a big pitcher plant happy.
Q: And so, in the winter, say there was a lot of rain and there was water all the way up to the drainage holes and then it freezes into a block of ice in the winter.
A: They love it they're fine no problem no big deal yeah it happens in the wild all the time.
Q: Then you just water that from the top?
A: Yeah, so I water it from the top and how do you know when you got it watered well enough? Yeah, it starts dribbling out the sides and once it starts dripping out the sides you know you got it right. So that's the easy way; the in-ground way you have to make sure your overflow is about that far below the surface of the water that the whole thing is level across the entire thing to keep it right. And we do some pretty low-tech things like put in a little peephole so I can see where the water level is, and we can fill it. This one actually has a fill on the sides, yeah fill is under this. It actually has a fill there and this fancy one here has a layer of gravel with frost cloth on top of it which keeps the peat on top and we can fill the reservoir from below and water the bog from below. So, it's pretty fancy. It’s never going to be as good as this because every time it rains stuff washes into the bog and that has nutrients. yeah, yeah so, it's never as good in the ground as it is in a pot and my favorite way to make in-ground bogs is on the high point in the landscape where nothing will roll into it, and I raise the lip up about two three inches above the soil.
Q: So, is it okay to get like one of those big kiddie pools?
A: Kiddie pools are great, yes absolutely. Okay, just leave the lip above and hide it somehow.
Q: What kind of water? Tap?
A: So yeah. So over a long period of time tap water has lots of salts and minerals in it. So, as you're watering it with tap water and you're not flushing it with tap water, not flushing it out to release those things out as they evaporate, they're going to leave salts behind and so slowly your plants will start to do more poorly. So, every four or five years I generally dismantle these things. If you can go four years in one of these without dismantling, you're doing something wrong because if you plant one pitcher plane it should be bursting out the sides.
Q: What about well water?
A: Well water can be just as bad. If it's hard water, it's going to be just as bad because these things really are fed with rainwater which is nothing, right. so, no nutrients. so, some people that are really very obsessive about this will buy distilled water or an RO unit for their house, so they have reverse osmosis water to put into their carnivorous plants.
A: A rain barrel’s perfect. or you know or just you're going to have to… these plants are going and will continue to grow, grow, grow. You’re going to have to take them out and divide them anyway so why not just replace it every four years. That’s my way of doing it.
Thank you, guys, so much. Thanks for being here today. if you haven't tried carnivorous plants, we got an amazing selection. I'm up there in greenhouse four. Take some home with you. Even if you can't plant it for a while, all you gotta do is put your pot in a little dish of water and it'll be fine for a long time.
Q: So just leave them out all winter?
A: All winter. Leave them outside.
Q: And so, the little Orchid could go in with anything, all of them.
A: Yeah, the grass pink Orchid is super easy to grow under the same conditions. So, there's others. The begonia, there's a number of different water spider orchids, and platantheras, which are called fringed orchids, the harperocallis that we sell is a wonderful accompaniment. We put all the plants that go with pitcher plants right with our pitcher, right with our carnivorous plants, all right. Thank you, guys.
Q: And so, the little orchid could go in with anything all of them.
A: Yeah, the grass pink orchid is super easy to grow under the same conditions. So, there's others. the begonia, there's a number of different water spider orchids, and platantheras, which are called fringed orchids, the harperocallis that we sell is a wonderful accompaniment. We put all the plants that go with pitcher plants right with our pitcher, right with our carnivorous plants, all right. Thank you, guys.