Houseplant Toxicity Week: Part 2 (Crazy Super Dangerous Plants)

If you have landed on this page because you are concerned about a child or pet who has eaten a plant, seek emergency medical help.

In the U.S., you can call Poison Control at 1-800-222-1222 (for children), the ASPCA at 1-888-426-4435 (for pets; $60 consultation fee applies), or the Pet Poison Helpline at 1-800-213-6680 (pets; $35 fee applies).

Part 2 of a seven-part-and-two-appendix series. (Part 1) (Part 3) (Part 4) (Part 5) (Part 6) (Part 7) (Appendix 1) (Appendix 2 - Index)

In part 2, we cover the plants that are crazy super dangerous to, you know, living things in general, and human beings specifically; these are the Chuck Norrises of the plant world. ("They once made a Lantana camara toilet paper, but it was a flop, because it wouldn't take shit from nobody."¹) Fortunately, and I guess also logically, most of the plants on this list are not really all that commonly grown indoors, because they're difficult, or nobody wants them because they're crazy super dangerous, or whatever.

Adenium obesum, unknown cv.
Adenium obesum (desert rose, mock azalea) Disrupts heart much like digitalis ('foxglove") and contains similar toxins; highly dangerous to humans and animals alike. Used in Africa as a freaking arrow poison and everything. (More about toxicity of Adenium at its profile.)
Alocasia spp. (elephant ear, taro) Edible if cooked in a particular way, but the raw plant is surprisingly vicious,² particularly the species A. macrorrhiza. Like Dieffenbachia spp., it appears to contain something besides irritant calcium oxalate crystals. See footnote for gory details.
Brugmansia spp. (angel's trumpets, tree datura) Though not often kept as a houseplant (not least because it's really prone to spider mites indoors), Brugmansia spp. are common enough and dangerous enough to include here. All parts of the plant contain the hardcore toxins atropine, scopolamine, and hyoscyamine, and are dangerous. This plant is sometimes deliberately abused by the stupid and/or impressionable because hallucinations are among the symptoms.³ Unfortunately, also among the symptoms are, you know, dying. (Also: flushing, dry mouth, rapid heartbeat, high blood pressure, fever, dilated pupils, freaking grand mal seizures, coma, surprise nudity,⁴ a second day of hallucinations, a third day of hallucinations, a fourth day of hallucinations, confusion, disorientation, violent agitation, etc.) There is a partial antidote (physostigmine) in cases where the plant responsible is known, but still: that's a hell of a lot of trouble to go to just to see pretty colors. Do whatever drugs you want, kids, but please don't do this one.
Or crystal meth. Don't do crystal meth, either. And actually heroin is bad too, I hear. Don't start smoking either. Actually no, I take it back: just don't do drugs. It's easier.
Colocasia spp. (elephant ear, taro) By association with Alocasia spp., q.v.
Datura spp. (devil's trumpet, jimson weed, sacred thorn apple) As for Brugmansia spp., q.v.
Euphorbia cooperi I'm listing E. cooperi in the crazy super dangerous category even though I found no evidence of it actually killing anybody. The reason for this is that it's so incredibly nasty that it's possible to get eye and nose irritation off of the vapor of a cut plant in the same room. If it's dangerous to smell the plant, then I think it qualifies as crazy super dangerous. (Link: the story in question is at the top of the page). And god help you if you happen to get some of the sap in your eye, or on your skin. There's nothing out there about ingesting E. cooperi, but I would assume that it would at least make you wish you'd never been born. It might or might not kill you.⁵

Euphorbia tirucalli
Euphorbia tirucalli (pencil cactus) There is one undocumented case at one site of a man who died from ingestion of E. tirucalli (Apparently the idea was to cure his sterility. Which to be fair, in a sense it did.). Even if it doesn't kill you, some people react strongly to the sap (bleeding sores are not unheard of), and getting sap in the eyes is agonizing, I hear. Contact with eyes will almost always result in temporary blindness, and in some cases, the eye may be permanently damaged, though permanent damage doesn't appear to be common. Wearing goggles when pruning is a rilly rilly good idea, and it's also probably a good idea to wash any exposed skin well (you may want to soap up multiple times) after you've dealt with the plant, as sometimes traces of latex can remain on you even when you've washed, and then all you have to do is wipe your eye with the back of your hand and we're back to the pain and temporary blindness again. (UPDATE: My first-hand account of getting a tiny speck of dried E. tirucalli sap in my eyes can be found here. Spoilers: I absolutely believe that getting sap squirted directly in the eye would be agonizing.) This is one of the few plants that I personally react to: I took some cuttings at work and washed up afterward, but a few hours later I noticed a red, inflamed-looking spot on the inside of my elbow. It didn't hurt or burn or do anything, but I'm pretty sure it was from the Euphorbia, and I took it as a warning to wash better in the future. Toxicity of Houseplants says the carcinogenic potential of this species is low, contrary to what I'd said in my profile on this plant.
Gloriosa superba (glory lily, climbing lily, gloriosa lily) This is another one that I see more often in the houseplant books than I have in real life. In fact, to the best of my recollection, I've never seen it in real life. All parts contain colchicine, which is a very poisonous compound also found in the autumn crocus. Colchicine stops the formation of microtubules, which if you don't know what microtubules are probably doesn't sound that bad, but it turns out that they're sort of essential for staying alive and stuff. Poisoning by Gloriosa goes on for a long time and involves what Handbook euphemistically calls "intense gastrointestinal symptoms," which the words "intense" and "gastrointestinal" together are never good.⁶
Jatropha spp. (jicamilla, physic nut, bellyache bush, coral plant, etc.) Only J. podagrica is kept as a houseplant, and then not very often, though I have seen it for sale at Wallace's, in Bettendorf IA, so I know it's out there. The seeds are definitely poisonous; it's less clear to me whether the rest of the plant is. The toxin, jatrophin, is similar to the more famous ricin, from castor beans (Ricinus communis, q.v.). Fatality is not inevitable, but it does happen. I think it's probably a safe bet that these are also toxic to pets.

Lantana camara 'Landmark Yellow.'
Lantana camara (lantana) I don't know if it's uncommon indoors because it's difficult, or because people don't like the smell, or because it's dangerously toxic, or what. I know I've thought about trying to grow some indoors, after dealing with them at work (they're sold as annuals here). It's a little unclear whether the whole plant is toxic; most human poisonings appear to involve the unripe berries, but poisoning seems to be a much bigger danger for livestock, who ingest the entire plant. Animal poisonings often involve liver and kidney damage, loss of appetite, constipation, jaundice, skin which variously peels, hardens, cracks, or turns raw and inflamed. Human fatality from the unripe berries is uncommon but does occur, and even in the cases where the person (usually a child) doesn't die, hospitalization over several days may be needed. This is probably a more serious danger to pets than to children.
Nerium oleander (oleander) This is not a common indoor plant, though it could probably be done in a sunroom or similar arrangement, and I have sold one as an indoor plant at work (after making fairly certain that the customer knew toxicity was potentially an issue). Like Adenium obesum, to which it is related, the whole plant contains toxins which affect the heart, and in high enough concentration that people have been known to exhibit poisoning from eating marshmallows roasted on Nerium sticks, or drinking the water in which Nerium flowers had been placed. Human toxicity is not inevitable but is common enough to be scary; I didn't find any reports of pet toxicity but I expect (due to smaller body size) pets are more at risk.
Plumeria spp. (frangipani) Neither Toxicity of Houseplants nor Handbook of Poisonous and Injurious Plants mention Plumeria, but 1) it's in the same family as Adenium and Nerium, so at the very least, caution is warranted, and 2) this site says that Plumeria, though it's not widely known, can cause most of the same problems as the more toxic Euphorbia species, including blindness from getting sap in one's eyes, severe skin irritation if sap drips on skin, and severe pain and possible death from ingestion of plant parts.

Rhododendron NOID.
Rhododendron spp. (azalea) Not all Rhododendron species contain grayanotoxins (the group of related compounds responsible for Rhododendron toxicity), but the nonscientist is advised to treat them all as though they did, because what with hybridization and so forth, it's more or less impossible to know unless you test each of your plants individually. Grayanotoxins block cell sodium channels, which lead variously to: heart arrythmias, low blood pressure, vomiting, slowed heartbeat, coma, diarrhea, irritability, excessive salivation, burning sensations in the mouth, tingling in the skin, dimming vision, muscle weakness, headache, convulsions, and death. Individual cases show wide variation, probably because individual plants may contain very different amounts of grayanotoxins and individuals consume very different amounts of plant. Rhododendron spp. are also definitely known to be lethal to cats; the reader should probably assume that this applies to most other pet species. The toxin is also found in the nectar of flowers, so honey made from Rhododendrons can be toxic as well. And yes, people have died from the honey.⁷
Ricinus communis (castor bean) This is more typically a garden plant than a houseplant, and probably, actually, if you see someone growing it as a houseplant, you might want to stay away from them in the future, 'cause this suggests that they want to grow it but they don't want anybody to know they're growing it. In the garden, Ricinus communis is kind of difficult to hide: it gets huge (in the tropics, to 15 feet tall: a co-worker tells me one she planted in her garden many years ago reached 8 feet in a single growing season). The seeds contain a highly toxic protein, ricin, which is easily absorbed only if the hard seed coats are broken: intact seeds generally do not cause any problems if swallowed whole and intact. Purified ricin is occasionally used as a murder weapon, most famously on the Bulgarian dissident Georgi Markov in 1978 (an umbrella was modified to actually shoot a pellet of ricin into his leg: it's an interesting story). It does, however, seem to be an awful lot of trouble, and the amount of time spent growing the plant and purifying the toxin and all that inevitably leaves a trail of some kind. I mean, if you're reading this post to get ideas about how to murder people, there are simpler ways. Also people are increasingly hip to the toxic potential of ricin, and the authorities do semi-regularly catch people plotting to kill others with it. (Also to be considered: it's just as toxic to you as it is to your intended victim. I mean seriously.) This is not the murder weapon you are looking for.

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Photo credits: My own. The Lantana picture is new, even.

¹ That joke didn't really translate very well, did it? I'm finding it difficult to get the mental image of Lantana toilet paper out of my mind. Gosh, but that would be unpleasant. [pause] Maybe the better joke would be, ". . . but it flopped, because nobody wants to give Lantana any shit." Better? Worse? Just kinda nonsensical?
² For those in the reading audience who were surprised to see this on the most-dangerous category: I know. I was too. But at least A. macrorrhiza belongs there. Toxicity of Houseplants has the following to say on the subject: "Biting or chewing any plant part causes severe pain in the mouth, throat, lips, and stomach. Touching the lips after handling the flowers can cause unbearable pain. Fatalities in children have been reported after ingestion of portions of the root or leaf. Delirium and death occurred within 6h. . . . Intense eye pain has been described after splash contact with plant juices." If it can kill children, I think it belongs in the crazy super dangerous category. As unpleasant as Dieffenbachia is, I was unable to find any account of it actually killing anybody (though I suspect from some of the descriptions that it made people want to die), so Alocasia winds up on the more dangerous list. Not all Alocasia spp. are necessarily this bad, but since they're hard to tell apart unless you're an expert, and since there's a pretty severe penalty for biting one even when it doesn't kill you, they may as well all wind up here.
³ Pah, I say. Just get sloppy drunk and watch Coraline, and save yourself a lot of trouble.
⁴ Less fun than it sounds. Case report reprinted in Toxicity of Houseplants reads, in part, "A 15-year-old boy found wandering naked and delirious developed profound muscle weakness and a seizure shortly after admission. Systolic hypertension, tachycardia, fever, dry mouth, flushed dry skin, and dilated pupils were noted. . . . Visual hallucinations continued for 4 d."
⁵ It should not surprise regular PATSP readers to learn that since finding this out about the species, I've wanted an E. cooperi desperately, though when I had the chance to buy one a while back, I didn't. I don't know why this is. Either thing -- the wanting to buy or the failing to buy. I don't understand either one of them. I'm very complicated. I contain multitudes.
⁶ The more detailed list, from Handbook and Toxicity of Houseplants, includes pain in the mouth, pain in the stomach, severe, profuse, persistent diarrhea (which often leads to equally severe and persistent dehydration), bone marrow suppression, collapse of the circulatory system, shock, hair loss, dramatic drop in blood pressure, inability to urinate, continuous vomiting, increased heart rate, etc., eventually climaxing in, usually, respiratory failure and death.
⁷ Or, well, maybe they've died from the honey. Apparently whatever site I got this from (it wasn't Toxicity or Handbook) neglected to add that this derives from a couple very, very old stories of questionable accuracy, and that nothing like this has been confirmed (or even, apparently, claimed) in a couple thousand years. There have, however, been claims of nonfatal poisoning of honey by Rhododendron nectar as recently as the mid 1980s; however, these cases were in Turkey and Austria, and I have no idea how I would go about confirming any of them. Toxicity does include a reference to heart arrythmias being induced by honey containing grayanotoxins, from 1988, which I would expect to be well-documented and confirmed and everything. So . . . maybe lethal honey has happened to a handful of people, over the last several thousand years, out of the 106,000,000,000 people who have ever lived. I wouldn't lose sleep over it. PATSP regrets the error.