Houseplant Toxicity Week Appendix 1: Euphorbia pulcherrima

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).

First appendix to the seven-part-and-two-appendix houseplant toxicity series. (Part 1) (Part 2) (Part 3) (Part 4) (Part 5) (Part 6) (Part 7) (Appendix 2 - Index)

From last winter at work.
I'm not going to link to it, but a thread at Garden Web recently got me kind of riled up, and since it was related to houseplant-toxicity issues I figure I'm never going to have a better opportunity to talk about it than this week.

The thread in question was initially conceived (not by me) as a thread to remind people that plants are sometimes dangerous, and get conversation started about which ones those were. Harmless enough, and potentially helpful, and I was already researching for this series at the time, so I was on board with that and actually interested. But. The person who started the thread also listed poinsettias, (Euphorbia pulcherrima) as one of the toxic plants in question. I took issue with this, as poinsettia toxicity, though still heatedly debated in hobbyist circles, appears to be a settled issue among scientists and other people who study this kind of thing. So I said hey wait a minute, and the other person said hey wait a minute yourself, they're toxic, everybody says so, and I was all like, the hell they do -- what about this and this, and then they said well but they give my son hives, and so on and on it went until I finally just said, the hell with this, and quit posting.

And that still wouldn't have been enough to make me do a whole blog post about it, except just after I left the thread, the person I had been arguing with returned just to note, smugly, that the ASPCA website lists poinsettias as toxic. Granted, s/he added a wink emoticon. But still. This was after I'd already said I wasn't going to add any more to the thread, so it was kind of a jerkish, I-get-the-last-word maneuver, I think. Whatever. Anyway. This gets me even more riled, because I really don't think the ASPCA should be considered an authority on houseplant toxicity until they can at least figure out how to tell an Anthurium andraeanum from a Hypoestes phyllostachya from a Soleirolia soleirolii,¹ never mind the somewhat complicated and nuanced Euphorbia situation.

So anyway. Since I have a blog, I can have the last word, at least as far as I'm concerned. And as long as s/he never reads this, then s/he can have the last word too, from his/r perspective, and everybody's happy. Kind of.² And now that we've established that I'm doing this out of some sort of twisted, desperate need to be right, we can move on to the evidence.

Beginning to color up. I like them best this way, when they're still mostly green.
Almost everything written about poinsettia toxicity mentions at some point or another that the plant is alleged to have killed a 2-year-old child in Hawaii in 1919. What some of them will fail to tell you is that this is apparently the last time that any poinsettia has been blamed for any human death. What even more of them will fail to tell you is that we're not even all that terribly sure about that one case: 1919 was a long time ago, and I can come up with any number of alternative explanations for why this could have been reported that way even if the actual cause had nothing to do with poinsettias.³ And even if the story actually was, "child eats plant, child dies," we still kind of need an explanation for why this hasn't happened again. It's fishy. And I do have a theory, which we'll get to.

Toxicity leads its profile of Euphorbia pulcherrima by saying that most Euphorbia species contain "diterpene esters," which are believed to be the active toxic principles in species like and E. tirucalli and E. cooperi, but that "there is considerable evidence that the quantity of these compounds found in the standard poinsettia sold by greenhouses is quite small or may be nonexistent." (emphasis mine)

Handbook is in agreement: "[Euphorbia pulcherrima] produces either no effect (orally or topically) or occasional cases of vomiting. This plant does not contain irritant diterpenes." (emphasis is mine again)

NOID varieties. Picture is by "arquera," at flickr.com.
Neither book seems to be trying to claim that there's never any reaction at all: skin irritation is definitely known, and some people are allergic. Allergies are especially likely to develop in people who work with the plants professionally: Toxicity cites a study of nursery workers for skin reactions, and found that allergic skin reactions generally occurred only after three years of occupational exposure,⁴ and that whatever was causing the reactions was probably not a terpene ester,⁵ which are what cause the reactions to other Euphorbia spp.⁶

It's also not unheard of at all for vomiting to develop following ingestion of poinsettia latex. This shouldn't surprise you if you've been reading through the series of posts so far, because you've seen that vomiting is a common symptom of ingestion of any poisonous plant, potentially lethal or not. Even then, though, the Poison Control data Toxicity gives from 1973 is, 228 ingestions of poinsettia were reported, and only 14 of those (6%) showed any symptoms at all. (Of that 14, vomiting was the worst the symptoms got.) Similar numbers from 1987: in 1987, the American Association of Poison Control Centers received 2611 reports of poinsettia exposure, of which exactly zero resulted in "deaths or major symptoms."⁷

And if we're talking about just pets, this page has not only another batch of information on children exposed to poinsettias (22,793 cases over eight years, and 92.4% of the cases had no reported effects. Not even a sick tummy. Nothing. Of the remaining 7.6% of cases, "stomach irritation" was the most common result. But remember, twelve out of thirteen kids had nothing happen at all. Those are pretty good odds.), plus a report about pet exposure:

. . . a 1998 report on pet ingestion of poinsettias showed that 15 dogs had ingested poinsettias, with three becoming ill — vomiting and diarrhea. Of the 51 cats in the report that ingested poinsettias, one was reported to have the side effect of excessive salivation.

Terrifying though drooling cats may be, they're not dead. So I wish people would calm down.

In the original thread, this was met with a response along the lines of, well, but allergies! There could still be allergies! We must warn the public! Think of the chillllllllldren!⁸ To which I say, well, okay, we can include poinsettias on the "toxic plants" list, but if we're going to include every plant that could ever conceivably harm anybody, then we'll have to include strawberries, kiwis and peanuts (allergies), lettuce and spinach (E. coli), potatoes, tomatoes and eggplant (solanine), celery (psoralens), apples (cyanide), rhubarb (oxalic acid), cashews (dangerous if unroasted), soybeans, wheat, rice, corn (allergies), and so on. If all of our food plants are things that we have to warn people about too, then clearly a line should have been drawn somewhere and wasn't.

Unknown variety. Picture is from anonymous Garden Web photo donor and is used by permission.
So here's my position on this. Any plant can cause harm, if you define "harm" broadly enough. Among other things, human immune systems are specific to the individual, and so in theory absolutely any plant could trigger a fatal allergic reaction. We don't warn everybody about plants in general, though, because 1) allergic reactions that kill people are not, actually, all that common, and 2) allergic reactions don't have a lot of anything to do with the plant in question. I.e., yes, you can get hepatitis from broccoli, but it's not the broccoli doing it: it's the hepatitis virus on the broccoli: the broccoli is blameless. In a similar way, poinsettias might be able to trigger some allergies, but it's not really the poinsettia doing it, it's your immune system going haywire and causing the problem; it's just using the poinsettia as an excuse. It's one thing to warn people about Brugmansia The Toxic Plant, because Brugmansias reliably contain atropine and scopolamine, and atropine and scopolamine reliably make people very ill or dead. But I think it's a little far to the paranoid side to warn everybody about poinsettias, because poinsettias typically have no effect on people, and even in the worst cases, they don't do anything major.

I do understand that allergies are unpleasant. I have some myself,⁹ and I don't like them, and it's nice to have a heads-up about that. And poinsettias do sort of appear to be better at triggering allergies than a lot of other plants. Some plant families are that way. But I don't feel like I can honestly class poinsettias as "Dangerous" when they don't seem to pose any danger to most people. So I give them a rating of Unpleasant, but that's as far as I'm willing to go.

One last note: I said I had a theory as to why poinsettias might have been toxic at one time but wouldn't be any longer. My theory is that we're looking at, more or less, evolution. I mean, it's evolution without natural selection, but it's still selection.¹⁰ People have been developing new varieties of poinsettia for about a century now, and for the most part, they've been doing so by breaking genes at random and sifting through the wreckage to look for anything that's broken in an interesting way. This can be done through purely human means, by exposing large numbers of plants to radiation and seeing if anything interesting shows up,¹¹ or it can be done with an assist from the plants themselves, by selecting naturally-occurring mutants and propagating them, or inbreeding them, or whatever.

When people look for new varieties of poinsettia, they're interested in bract size and color, compact growth habit, maybe leaf shape, bract texture, the color pattern on the bracts, and so forth. They're not normally particularly interested in the toxicity of the plant.

Now, producing a toxin is normally a fairly complicated process, and requires a lot of different steps, each one facilitated by a particular protein molecule called an enzyme, and in many cases these enzymes can be themselves regulated by the action of other molecules in the plant, such that feedback loops get set up, where an enzyme that combines A and B into C stops working once there's a sufficient level of C in the surrounding area. And then C may combine with D to produce E, unless there's a high concentration of B around, in which case C combines with B to produce F, and so on. It can all get pretty complicated pretty quickly, as you can imagine. So the production of a toxin (or anything else in the plant, for that matter) requires a lot of energy and resources, and depends on the proper functioning of every step in the process.

Assorted varieties. Clockwise from top: 'Christmas Feelings Pink,' 'Classic White,' 'Cortez Burgundy,' 'Picasso,' 'Miro,' 'Prestige Red,' 'Sonora White Glitter.' The last of those is my favorite, though it didn't photograph terribly well here.
In the wild, assuming that wild-type poinsettias even produce toxins in the first place,¹² the whole complicated chain is preserved through natural selection: any plant mutated in such a way that it fails to produce the toxin gets eaten, doesn't pass on its genes, and the error dies with the plant. If you're cultivating poinsettias and trying to find new varieties, though, you're probably protecting the plants yourself, either through a very sterile environment, or by regular applications of pesticide, or through some kind of beneficial-insect pest control, or whatever, so a plant that fails to produce toxin is not penalized in the same way. In fact, if a mutation arose in a plant that made it noticeably more toxic, that plant would probably just be destroyed, because no plant breeder/developer wants to have rashes all the time any more than you do.

The logical end result of a century of cross-breeding and genetic manipulation is a species which has all non-essential genes broken, including the ones that lead to toxic products. I have no proof that this is what's happened, and I have no proof that there were ever toxins in Euphorbia pulcherrima in the first place, but this all seems really logical (to me), and would explain how a species which was toxic enough to (allegedly) kill someone 90 years ago would now be so harmless that it can barely get one dog out of five to barf.

Alternative baseless theories are welcome in comments, as are firsthand experiences, actual scientific evidence, or just people stopping by to say hey.

Tomorrow's post will just be the index for the series in general, assuming that I get all the links added in the right places, and will be profoundly boring. Regular PATSP posting will resume on April 26.

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Photo credits: Mine except as otherwise indicated.

¹ The ASPCA, as I noted in the original part 7 post (it has since been moved to part 4, as I have become convinced that it really is toxic), has a listing for "baby's tears," accompanied by a picture of a red Anthurium andraeanum flower, with the botanical name Hypoestes phyllostachya slapped on it.
Hypoestes phyllostachya is a small weedy plant with pink spots (occasionally red or white) on a dark green leaf, small purple flowers, and a prostrate habit. It usually goes by the name "polka-dot plant," and occasionally as "freckle face." Very rarely, I've seen it as "baby tears," though I don't understand what "tears" actually refers to: I know what the "polka dots" are, and I understand "freckles," but "baby tears" is just confusing.
Anthurium andraeanum is a large upright semi-epiphyte with enormous spathe-and-spadix flowers, generally in pink, red, orange or white, and large solid-green leaves. It's typically called "Anthurium," but I've heard the common names "flamingo flower," "tail flower," and "oilcloth flower."
Soleirolia soleirolii is a spreading, low green plant with tiny leaves that forms dense mats of foliage. If it flowers, the flowers must be pretty damn inconspicuous. It's usually called "baby tears," which is probably how it got caught up in all this.
It seems like it would be difficult to mix these up. But ASPCA has. (Just so you know, ASPCA: I work cheap.)
² Garden Web's forums have been irritating to me anyway, for a few months, and I've been posting a lot less as a result. I'm not sure what it is exactly. I mean, this thing with the poinsettia person is not actually that big of a deal to me, and aside from him/r being kind of jerky on this one particular matter, I like him/r fine. It's more that I'm getting bored with answering the same four or five questions over and over again. There have been days when I've felt like, if just one more person, just one more, writes another post about OMG what are these fruit flies doing flying all over the place around my plant and what kind of really poisonous spray can I buy to make them all disappear, I will completely lose my shit. (A: They're actually fungus gnats, not fruit flies, and they mean you're overwatering, so stop overwatering and the flies will go away on their own.) And peace lily questions, too: I get tired of the peace lily questions, 'cause they're always the same thing, and for a while there I was answering them once or twice a week. It may not be reasonable of me to expect people to use the forums' search function to see whether their question has maybe already been answered fifty times before writing a new post about it. Probably some people actually were using the search, and I don't think about them because I never have to deal with them because they're answering their own questions. But anyway. Not the point. The point is that Garden Web got, or is getting, boring and irritating to the point where I'm just really not interested in it anymore, and some of the other people who actually knew stuff and were interesting to hear from have hit this point too and are no longer there, which is even less incentive to go back, and so here we are. It's still a pretty decent resource for getting plant questions answered: I've just lost patience with it. Whether this will be permanent or temporary, I'm not sure.
³ Perhaps the child's father was violent but well-connected, and beat the child to death but convinced the doctor to record the cause of death as due to poinsettias, so he could avoid murder charges. Maybe the child ate several different plants at once, and the other plants were the ones that killed him/r. Perhaps more than one species was known as "poinsettia" at the time (especially if those involved were using Hawaiian-language names for the plant), and the wrong species got blamed.
⁴ Inquiring minds want to know: continuous occupational exposure, or seasonal occupational exposure? It doesn't say. WCW, who has dealt with the points for five or six consecutive Christmases at work, perked right up when I mentioned this. Though neither she nor I have experienced any symptoms of anything so far, so maybe it's continuous occupational exposure and we're both safe for another few years.
⁵ Off-topic, but what the hell, we're in the neighborhood: terpenes are a class of smallish organic molecules which are produced by all kinds of organisms. They're special for a variety of reasons: they are often aromatic (see limonene, menthol, pinene, geraniol, etc. Technically, menthol and geraniol are terpenoids, but the distinction is minor for our purposes and we're already off-subject.), they're used as signaling compounds by plants and animals, they often have unusual or complicated structures, and although not all of them are toxic (in fact, you couldn't live without some of them: Vitamins A and K are closely related to terpenes, as are all steroid hormones and cholesterol), the toxic components of the really nasty Euphorbias, compounds like phorbol, ingenol, and resiniferatoxin are terpenoids. What distinguishes a terpene from a non-terpene is that terpenes are built up from a number of small, branched five-carbon units, and non-terpenes, however aromatic, complicated, or useful to living organisms, are not.
⁶ To my mind, this makes the most likely culprit in E. pulcherrima a protein, as proteins often produce allergic responses and they can be dissolved in water, unlike the diterpene esters -- diterpene esters were ruled out because the subjects reacted to water extracts of the sap, and diterpene esters are apparently not water-soluble. Or at least not water-soluble enough. I should probably admit that I don't know what the actual numbers are for the water-solubility of the various Euphorbia diterpene compounds, and I would bet you $100 that you don't know either. (Bet you $1000 that you don't even care.)
⁷ This leaves open the question, of course, of what constitutes a "major symptom." But still. It's probably something worse than throwing up.
⁸ Somewhat exaggerated for comic effect.
⁹ So far, mostly just cats, and a few individual dogs but not dogs in general, plus Ficus benjamina sap, as far as I've actually been able to prove to myself. I probably do have other allergies, and just don't know what they are.
¹⁰ I personally feel like the distinction between natural selection and artificial selection is sort of an arbitrary and meaningless one. It matters not one bit to the genes in an apple tree whether they prosper due to humans or due to some other species of animal: what matters^a to the genes is whether or not they have qualities that enable them to spread or not. Whether they're spreading in an environment that includes squirrels and mild winters, or in an environment that includes laboratories measuring fruit sugar content and machinery that puts a premium on fruits with harder, less-bruisable flesh, the outcome is still the same: the plants that produce fruits that withstand squirrels and mild winters prosper in the first scenario, and the plants that produce hard-fleshed, sugary fruits prosper in the second. We are now the "natural environment" of the trees, to a huge extent, as far as I'm concerned, even if we weren't originally. So I don't really care whether it's "natural selection" or "artificial selection," because I think artificial selection is natural selection. We, after all, have just as much right to be here as the trees do: we just have the handicap of sometimes feeling guilty about it.

^a Genes are inanimate, nonsentient, transient entities with no conscious awareness of anything, so it's not correct, strictly speaking, to say that anything "matters" to them. But if the reader is able to think strategically, from the point of view of a gene, the point I'm trying to make might be clearer.

¹¹ The irradiation method is used a lot more than you'd think, including in some food plants. It's unnatural, technically, but more in degree than in substance: natural mutations are also generally caused by high-energy particles like those from cosmic rays or radioactive decay changing the sequence of DNA in an organism, but this is not an incredibly common occurrence, and it's even less common for it to happen in a cell that goes on to produce a seed or a shoot that will make the change obvious. Artificially irradiating plants to mutate them leads to the same things happening in the cells, but many more cells are affected, and so the chances that something interesting and visible will be produced are greatly increased. Begonia rex-cultorum varieties are developed this way all the time. Exposing plants to radiation does not make their descendants radioactive any more than exposing a cow to light makes its hamburgers glow in the dark.
¹² To my knowledge, nobody has tested the wild-type poinsettias to see whether they are toxic or not, or even tested them for the presence of terpene esters.