Saturday, April 25, 2009

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)
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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 mattersa 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.


Friday, April 24, 2009

Houseplant Toxicity Week: Part 7 (Unknown / Could Not Determine Plants, and Conclusion)

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

These are the unknown/could-not-determine plants. For these, either I couldn't find enough information to determine whether they were harmful, or I found information but it was contradicted by other information that seemed equally good. (I think the best celebrity analogy would be Oprah Winfrey: is she good? Is she bad? All we can really agree on is that she's very powerful. Martha Stewart would work too.) In any case, I've included my best guess for each plant, but that's all it is, is a guess, and I am almost certainly wrong about some of these, possibly very wrong. With any luck, this list will dwindle over time, as more information comes in and I can move some of these out of here.

Adiantum spp. (maidenhair fern) I didn't see any specific references to Adiantum. My guess is that they're Potentially dangerous, but that's a pretty wild guess.
Alternanthera spp. (A. dentata 'Purple Knight') These weren't on any lists either. They have kind of a Safe vibe to them, but I don't actually know.

Ardisia elliptica.

Ardisia crenata (coral berry) There's very little information out there about Ardisia spp., and what there is is conflicting. The fruits, according to some sources, are definitely toxic, but in the wild they're distributed by birds, which has been one of the main reasons for the Ardisias becoming invasive in Hawaii and Florida and so forth. So they're not universally toxic, obviously. And nobody mentions the foliage at all. So I don't know. I would guess probably Potentially dangerous, on the grounds that the plant is at least known to be able to create toxins, whether they're restricted to the seeds or not.
Ardisia elliptica (shoebutton tree) As for Ardisia crenata, q.v.
Aspidistra lurida, A. elatior (cast-iron plant) These are on several lists, but the lists don't agree when it comes to Aspidistra. I guess Potentially dangerous.
Asplenium nidus, A. antiquum (birdsnest fern, Japanese birdsnest fern) Again, nothing on the lists; I'll guess Potentially dangerous just because that's what I guessed for Adiantum.
Asplundia 'Jungle Drum' Way too new to be on any of the lists. I'd guess Safe, if I had to guess, but that's based on very little.
Cereus peruvianus Cacti are more or less completely missing from houseplant toxicity lists. I suppose the spines make them hard to eat anyway, whether they're toxic or not. So we'll say it probably belongs in the Unpleasant list, as would most cacti. That said, there are a few genuinely toxic cacti out there, and I can't promise that C. peruvianus isn't one of them.
Ceropegia woodii (rosary vine, string of hearts) No information whatsoever, or at least nothing I could track down in time for the post. I would guess Unpleasant.

Chlorophytum comosum.

Chlorophytum comosum (spider plant, airplane plant, mala madre) Chlorophytums are generally considered safe by pretty much everybody, but a couple sources said that they were toxic to cats. This is believable, because they're in the Liliaceae, and there are quite a few things in the lily family which are specifically toxic to cats. However, it's also not believable, because the husband had a cat when I met him, and also a lot of spider plants, and she used to eat the spider plants all the damn time. And, I mean, yeah, she also threw up afterwards, all the damn time, but I always kind of thought that the throwing up was the point. At the very least there's a big difference between a vomiting cat and a dead cat. So I have no idea. I would still favor my actual experience and go with Safe, but I'm conflicted enough that the Chlorophytums wound up on the unknown list, pending more information about how they get on with cats.
Chlorophytum x 'Fire Flash' (Fire Flash, mandarin plant, green orange) As for Chlorophytum comosum, q.v.
Cyrtomium falcatum Some reputable-seeming sites list this as safe for reptile and amphiobian enclosures, but aside from that, no lists include them. If you held a gun to my head I'd go with Potentially dangerous. But please don't. Hold guns to my head.
Davallia spp. As for Cyrtomium falcatum.
Dionaea muscipula (venus flytrap) Another one with the toxicity equivalent of an unlisted phone number. My guess would be Safe.
Echeveria spp. I have no idea; to be on the safe side, I'd say Potentially dangerous, along with Kalanchoe and Tylecodon and all those other guys.
Eucharis grandiflora (amazon lily) Also not on the lists. It is also in the lily family, and grows from a bulb of sorts, two characteristics which tend to go along with being poisonous, so I'd think Potentially dangerous at least, and very probably Dangerous to cats.

Exacum affine.

Exacum affine (persian violet) Only on a few lists. Probably Safe.
Fatshedera lizei (tree ivy) Only rarely included on lists. Based on some of its relatives (Hedera helix, H. canariensis, Schefflera actinophylla and S. arboricola: Hedera helix is actually one of its parents.), I would guess at least Potentially dangerous.
Fatsia japonica As for Fatshedera lizei, except that the few lists that do mention it tend to consider it non-toxic, so I'm all conflicted.
Fenestraria rhopalophylla Basically an unknown plant, so of course it's not on the lists. Going with the general rule that any succulent you don't know anything about should be treated as, minimally, Potentially dangerous, I guess that's what I'll guess here too.

Gasteria 'pseudonigricans.'

Gasteria spp. I didn't come across any lists that mentioned Gasteria spp. separately. They're closely related to Aloe spp., which are toxic, as well as Haworthia spp., which are non-toxic, and I don't know which is the closer relation. My guess, if I were forced to guess, would be that they're probably Safe, though some species have sharp leaf tips which could theoretically be a problem, so they could be as bad as Unpleasant or Potentially dangerous.
Hatiora salicornioides (drunkard's dream) Again, most indications were that cacti are generally Safe except for the spines. This plant doesn't even really have spines, so it's probably either Safe or Unpleasant.
Hemigraphis exotica (waffle plant) Kinda too new for anybody to know much about them. I'd guess Unpleasant.
Hylocereus undatus (dragon fruit cactus) As for Hatiora salicornioides.
Murraya paniculata (mock orange, orange jasmine) Not on any lists; probably Safe in smallish amounts for humans, birds, reptiles and amphibians, considering the uses to which it's been put, historically speaking. On the other hand, it may, like the Citrus spp. to which it is related, cause vomiting and diarrhea in cats and dogs. I don't know whether the small reddish fruits are likely to be safe or not. Wouldn't risk it.
Ophiopogon spp. (lilyturf, Liriope) Not mentioned by anybody, and -- despite what strikes me as perfect suitability for indoor culture, almost never grown indoors. I expect Potentially dangerous, because it's in the Liliaceae, and most of the Liliaceae appear at the very least to be toxic to cats.
Platycerium bifurcatum and other Platycerium spp. (staghorn fern) This one I didn't think of adding to the list until late, so I haven't really looked for it on-line. Neither Toxicity nor Handbook mention it, though, and if there's a general rule for ferns, I haven't been able to find it so far. My guess would be Unpleasant, but that's based on practically nothing at all.
Podocarpus macrophyllus (buddhist pine) Not mentioned by Toxicity or Handbook; the web consensus appears to be that they're of little toxicological consequence, and only the fruits are toxic, causing nausea and vomiting if eaten, but I did run into one site that said that the entire plant was dangerous to pets and children, and that all parts of the plant except for the berry (the seed is toxic, but the flesh around the seed is not) are poisonous enough to kill a large animal. My suspicion is that the low-toxicity people are correct: there are at least a lot more of them. But all I know for certain is that you shouldn't eat the seeds. My guess is Unpleasant.

Radermachera sinica.

Radermachera sinica I guess it's still new enough that it hasn't made it to the lists yet, and there are no relatives I'm aware of. I find myself unable to even make a guess.
Selaginella spp. (spikemoss, resurrection plant, rainbow fern) Not included on any lists, though sometimes recommended for moist terraria. I suspect these are probably Safe, but am uncertain.

So except for a couple minor bits of housekeeping (a promised long post about poinsettia toxicity, which I will post tomorrow, and an index post, which will go up on the 26th), that's the Much-Anticipated and Necessarily Incomplete PATSP Survey of Indoor Plant Toxicity. Which should either be abbreviated MANIPSIPT or MANIPATSPSIPT, both of which look like something Bill the Cat would say. So maybe we'll just call it "The Toxicity List."

If you've:

1) been holding back a disagreement about the placement of a particular species, or
2) you want to tell me something about a plant from the above Unknown list, or
3) you think that even though you don't know whether it's toxic or not, I left off some personal favorite plant of yours and you want to see it go into the mix somewhere, or at least get investigated a little, now would be the time to speak up.

Tomorrow: I wade hip-deep into the ever-burning controversy about whether poinsettias are really toxic or not. Personal scores to settle! Animal testing! Alarmism! It promises to be a real page-scroller. Stay tuned.


Thursday, April 23, 2009

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

Part 6 is for the plants that, as far as I can tell, have never hurt anybody (like Meg Ryan ca. 1990? Maybe Ellen DeGeneres? Edie McClurg? Dianne Wiest?), and aren't capable of it in the amounts that most people or pets would be capable of consuming. It turns out that safety is kind of boring, so this list is a duller read than the others. I tried to insert jokes when I could, but also there's a music video if you're interested:

[Well, it was the video for "The Safety Dance." Alas, the company that owns the music doesn't want you to hear it, lest you enjoy it and think about buying it for yourself or something.]

But let's begin.

Aechmea fasciata.

Aechmea fasciata (silver vase plant) Bromeliads are safe under most circumstances and to most species.
Aeschynanthus lobbianus (lipstick plant) Gesneriads are safe under most circumstances and to most species.
Aeschynanthus speciosus (goldfish plant) Gesneriads are safe under most circumstances and to most species.
Aphelandra squarrosa (zebra plant, saffron spike) The few websites that include this by botanical name list it as safe; most of the ten other "zebra plants" out there are also safe, but it's nice to be told which particular plant is being approved of.
Beaucarnea recurvata (ponytail palm) I'm a little surprised at this one; it just has that toxic look. But there's fairly solid agreement that it's safe.

Begonia NOID. I have yet to find a good explanation for exactly what "Rieger Begonias" are and where they come from.

Begonia spp. (wax begonia, tuberous begonia) (Begonia rex-cultorum) Begonia spp. are essentially safe plants, though the rhizomes and tubers contain calcium oxalate crystals, like the Araceae, and may in theory cause similar pain and inflammation if chewed. If one is overwintering tubers, they should be kept out of the reach of children and animals, but no cases of Begonia toxicity were known to Toxicity of Houseplants, and Begonias are otherwise safe for children and pets, including reptile and amphibian enclosures.
Brassolaeliocattleya cvv. Orchids are safe under most circumstances and to most species.
Calathea spp. including Calathea ornata Plants from the Marantaceae are safe under most circumstances and to most species.
Cattleya spp. Orchids are safe under most circumstances and to most species.

Chamaedorea elegans.

Chamaedorea elegans (parlor palm) True palms are safe under most circumstances and for most species. (Caryota mitis is the notable exception. Other species known as "palms," e.g. the sago palm Cycas revoluta or the cardboard palm Zamia furfuracea, are quite dangerous, but they're also not true palms so they don't count.)
Chamaedorea metallica (metallica palm, miniature fishtail palm) As for Chamaedorea elegans.
Chamedorea seifrizii (bamboo palm) As for Chamaedorea elegans.
Chrysalidocarpus lutescens (areca palm) As for Chamaedorea elegans.

Cissus rhombifolia.

Cissus rhombifolia (grape ivy, oakleaf ivy) A large number of websites list this plant as being of unknown toxicity. Those which commit one way or the other all seem to go with non-toxic, though many of the sites listing Cissus as non-toxic also say a lot of other things are non-toxic, including some plants that I know are toxic. So I don't know. The ASPCA isn't worried about Cissus, several herp sites list it as being a good plant for reptile / amphibian enclosures, and the Vitaceae are generally safe as far as I'm aware, so I'm pretty sure that C. rhombifolia is fine. Even the sites that say it's toxic generally won't go any further than saying maybe you'll have some skin irritation.
Coffea arabica (coffee tree) There's fairly widespread agreement that Coffea arabica is safe, though occupational allergies or skin irritation have been known to occur among people who process coffee beans, which counts, but only just barely. Very young children may get very hyper after eating small quantities of the roasted beans, but this poses little risk to the child's health.1
Columnea spp. Gesneriads are safe under most circumstances and to most species.

Cordyline fruticosa 'Florica.'

Cordyline fruticosa (ti plant) Are in fact actually edible (discussed at some length in the profile), and are occasionally used as a foodstuff in some cultures. Safe except for the remote chance of an allergic reaction.

Crassula ovata. Admittedly not a good picture for trying to comprehend the overall shape and habit of the plant, but I thought it was pretty. And it's not like you can't see overall-shape-and-habit pictures a gazillion other places on line if you really want them.

Crassula ovata (jade plant) All the on-line lists have jade plants down as non-toxic, so I was really surprised to see Handbook cover it. Unfortunately, Handbook declined to say much of anything remotely specific. All they have to say is that it does sometimes irritate the skin, but that's rare, toxicity almost never happens and is never fatal, and we don't know what causes the toxicity when it does happen. So I think this is probably technically toxic, but only barely, and I'm inclined to call it safe for kids and pets: as many of them as are out there, if it could do any real harm, believe me, you'd have heard about it. (Toxicity mentions two studies of calls to poison control centers: in one, Crassula ovata was the second most called about, and in the other, it ranked fourth. The fact that so many people could be calling about it, but it's still getting listed as safe, suggests that it's probably fairly safe.)
Ctenanthe spp. (never-never plant) Plants from the Marantaceae are safe under most circumstances and to most species.
Dendrobium spp. Orchids are safe under most circumstances and to most species.
Ensete spp. (ornamental? banana) Should be safe under most circumstances; I don't know whether the fruit is particularly edible / tasty, though.
Episcia spp. (flame violet) Gesneriads are safe under most circumstances and to most species.

Fittonia albivenis. Sadly, we're out of these at work: I'd intended to get one for Nina, but she's going to have to make do with a Ctenanthe burle-marxii instead, it looks like.

Fittonia albivenis (nerve plant, mosaic plant) Almost universally recognized as safe. Particularly suitable for tropical terraria, as it stays small and can be pruned back as needed.
Fuchsia spp. Allergic reactions are rarely reported, but Fuchsia are otherwise safe. Not very commonly kept indoors.
Gardenia jasminoides (gardenia, cape jasmine) Generally understood to be safe. I did run into at least one source which said that it may cause slight problems for cats and dogs, but that this is not generally life-threatening. I don't know anything more specific than that, because I don't remember what site it was and that was the extent of the notes I took. I'm not sure I even believe it in the first place.
Gibasis geniculata (Tahitian bridal veil) Generally understood to be safe for all species.

Guzmania lingulata NOID.

Guzmania lingulata (scarlet star bromeliad) Bromeliads are safe under most circumstances and to most species.
Gynura aurantiaca (purple passion vine, purple velvet plant) Generally understood to be safe for all species. Some of the commenters at davesgarden.com say that it is poisonous, and davesgarden.com has it flagged as a toxic plant, but almost nobody else does. A closely related species, Gynura crepioides, is not only non-toxic but is actually edible, and goes by the common name of "Okinawan spinach."
Ludisia discolor (jewel orchid) Orchids are safe under most circumstances and to most species. This is a particularly good plant for reptile and amphibian enclosures, as it appreciates the humidity of a tropical terrarium, has attractive coloration, and is slow enough to be more or less manageable.
Haworthia spp. Generally understood to be safe for all species. Suitable for desert reptile enclosures, as it tends to stay a manageable size and has no sharp points or edges.
Hibiscus rosa-sinensis (tropical hibiscus) Actually edible; used as a foodstuff but not very often or by very many people. Occasionally recommended as a good plant for tortoise enclosures: they will eat the leaves and/or flowers.

Believed to be Hoya pubicalyx, though we won't know this for certain until it flowers. Which it's not looking real motivated so far, unfortunately.

Hoya spp. (H. carnosa) (wax flower) Hoya spp. are usually understood to be safe for all species. The nectar from flowers may be toxic if the plant has been treated with a systemic pesticide, but that's about the only time they're dangerous.
Laurus nobilis (bay leaf, laurel) Edible, though there have been some weird stories.2 Toxicity to pets is unclear, but I think it's probably safe.
Lithops spp. (living stones) These are apparently sometimes eaten in their native South Africa, for the water content, so I assume they're probably non-toxic. I mean, either that, or whatever toxic effects they have are not as bad as dehydration. But I think they're probably just not toxic. Not especially recommended for terraria, even desert terraria, as their watering requirements are fairly idiosyncratic and would be difficult to harmonize with other species.
Maranta leuconeura erythroneura (prayer plant) Plants from the Marantaceae are safe under most circumstances and to most species.

Maranta leuconeura kerchoviana.

Maranta leuconeura kerchoviana (prayer plant, rabbit tracks, ten commandments plant) Plants from the Marantaceae are safe under most circumstances and to most species.
Musa spp. (banana) Generally understood to be safe in the amounts swallowable by most pets or children.
Nematanthus spp. (guppy plant) Gesneriads are safe under most circumstances and to most species.
Neoregelia 'Fireball' (by association) Bromeliads are safe under most circumstances and to most species. 'Fireball' is an exception to the general warning about Neoregelia spp. (see yesterday's post) because it does not have spines.

A very small Nephrolepis exaltata.

Nephrolepis exaltata (Boston fern) Generally understood to be safe. Toxicity reports that skin irritation has occurred in nursery workers who handled the wet plants without gloves for long periods. I've experienced itching from wet fronds myself, but nothing horrible. Otherwise there doesn't appear to be a problem. Not especially suitable for reptile or amphibian enclosures, as they grow incredibly fast.
Oncidium cvv. Orchids are safe under most circumstances and to most species.
Paphiopedilum spp. (lady-slipper orchid) Orchids are safe under most circumstances and to most species.
Pellionia spp. including Pellionia pulchra Safe under most circumstances and to most species: this is one of very few species that the ASPCA website actually approves of.
Peperomia argyreia (watermelon plant) All Peperomia spp. are understood by almost everybody to be safe under most conditions.
Peperomia caperata / griseoargentea (Emerald Ripple) As for Peperomia argyreia.

Peperomia clusiifolia NOID.

Peperomia clusiifolia As for Peperomia argyreia.
Peperomia obtusifolia (baby rubber plant) As for Peperomia argyreia.
Phalaenopsis spp. (moth orchid) Orchids are safe under most circumstances and to most species.
Pilea cadierei (aluminum plant) Pilea spp. are understood by almost everybody to be safe for most species under most conditions, though they do technically contain a mild toxin.

Pilea depressa.

Pilea depressa (baby toes) Pilea spp. are understood by almost everybody to be safe for most species under most conditions.
Pilea nummulariifolia (creeping Charlie) Pilea spp. are understood by almost everybody to be safe for most species under most conditions.
Plectranthus verticillatus (Swedish ivy) Generally understood to be safe in most circumstances.
Rhapis excelsa (lady palm) As for Chamaedorea elegans.

Assorted Saintpaulia ionantha cvv.

Saintpaulia ionantha cvv. (African violet) Gesneriads are safe under most circumstances and to most species. Plants are, however, fragile and could easily be trampled to death in a terrarium containing large animals.
Saxifraga stolonifera (strawberry begonia) Generally understood to be safe in most circumstances.
Schlumbergera truncata cvv. (Christmas / Easter / Thanksgiving / holiday cactus) Generally understood to be safe in most circumstances. Some lists include Schlumbergera as toxic, especially for dogs and cats, but it's unclear what they're basing this on. So maybe slightly dangerous to pets; danger to children appears pretty minimal.
Sinningia speciosa (gloxinia) Gesneriads are safe under most circumstances and to most species. Plants are, however, fragile and could easily be trampled to death in a terrarium containing large animals.
Soleirolia soleirolii (baby tears) Generally understood to be safe in most circumstances. Often used as a ground cover in tropical or woodland terraria, since it forms a thick mat of easily maintained vegetation.

Streptocarpus 'Tanager.'

Streptocarpus spp. (cape primrose) Gesneriads are safe under most circumstances and to most species. Plants are, however, fragile and could easily be trampled to death in a terrarium containing large animals.

Stromanthe sanguinea 'Magicstar' (L) and 'Triostar' (R)

Stromanthe spp. Plants from the Marantaceae are safe under most circumstances and to most species.
Tillandsia cyanea (pink quill) Bromeliads are safe under most circumstances and to most species.
Tillandsia spp. (air plants) Bromeliads are safe under most circumstances and to most species.

Tolmiea menziesii.

Tolmeia menziesii (piggyback plant) Generally considered safe, though a few people develop allergies. Allergies are generally restricted to redness and itching and are not really a big deal. This would be suitable for reptiles and amphibians, though the plant does best in a cool, moist environment so that kind of limits its usefulness for tropical terraria.
Tropaeolum majus (nasturtium) Not often kept indoors, partly because it needs a lot of light and partly because it's really susceptible to spider mites, but the leaves and flowers are edible, and reportedly even taste kind of good. Sometimes recommended for tortoise enclosures because they will eat the flowers.
Vriesea spp. including Vriesea splendens (flaming sword bromeliad) Bromeliads are safe under most circumstances and to most species.
Zygocactus spp. (Christmas / Easter / Thanksgiving / holiday cactus) As for Schlumbergera spp., q.v. (Plants called Zygocactus are in fact actually Schlumbergera, and Zygocactus doesn't refer to any actual plants anymore, if it ever did.)

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Photo credits: This set was all mine.

1 It could have negative effects on the mental health of the parents or guardians, of course, which might indirectly threaten the health of the child, but it'd be tough to pin that on the plant.
2 Occasional freak accidents involving unchewed leaves obstructing windpipes or bowels have been reported, but if the universe wants to take you out badly enough that it does it with a bay leaf, then your number is probably just up, you know? Chew your food, or maybe take out the leaf when you're finished cooking the food.


Wednesday, April 22, 2009

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

Part 5 is about plants which are not likely to kill you, or even to result in serious injury, but which may be capable of causing vomiting, bad skin or eye irritation, diarrhea, burning, itching, or other bad things, things that you should avoid experiencing if at all possible. Like . . . I guess Paris Hilton?1 This is also the designation for a lot of the plants which are otherwise safe but bear thorns or spines that could puncture the mouth or digestive tract.

Abutilon hybridum (flowering maple) Causes skin irritation and/or allergic reactions in a few people; no info on pets but it does not appear to be particularly dangerous.

Acalypha reptans. I thought this was A. hispida for more than a year: boy is my face red.

Acalypha hispida, A. reptans (chenille plant, dwarf chenille plant) The sap appears to be able to irritate the skin and digestive tract, and skin irritation is occasionally reported. Although it is in the family Euphorbiaceae, it seems not to be a particularly dangerous plant (similar to Codiaeum variegatum, q.v.).
Alpinia zerumbet (shell ginger, variegated ginger) Occasional reports of skin and eye irritation, especially in people who habitually handle large amounts of plant material (e.g. commercial propagators). Toxicity by ingestion was not known to the authors of Toxicity. Minimal risk to the average indoor (or outdoor) gardener. Likely safe for pets.
Ananas comosus (pineapple) Leaves are pointed and spiny, which poses some mechanical risk. I know for a fact that the leaves can be eaten by rabbits more or less safely. Most pineapple-related medical problems are occupational: the uncooked fruit contains an enzyme which breaks down proteins, including those in skin (fingerprint loss is not unheard of), as well as sensitizing compounds which can cause rashes and other kinds of skin irritation. More or less safe around pets and children. Very soft-skinned reptiles / amphibians may be damaged by leaf spines. Unripe fruits can be extremely unpleasant if consumed (they're pretty hardcore purgatives, among other things), but don't appear likely to kill.
Araucaria bidwillii (bunya-bunya) Nobody seems to know whether Araucaria spp. are actually toxic, but this one is sharp and pointy enough that I can't imagine anybody wanting to try it to find out.

A small Araucaria heterophylla forest.

Araucaria heterophylla (Norfolk Island pine) Not mentioned by Toxicity or Handbook. Most websites list it as safe. Should be suitable for carnivorous reptiles and amphibians, and probably herbivorous ones too. The ASPCA website claims it's toxic to cats and dogs, but I kind of don't believe the ASPCA on this one.
Bougainvillea spp. (bougainvillea) Not common indoors, because it's hard to get the right conditions for it, but it won't poison anything if you can manage to make it work. Unfortunately it's also covered in thorns and can cause injury anyway, so deal with accordingly.
Capsicum annuum (chili pepper, bell pepper, etc.) Ingestion may cause pain, burning, etc., and in large amounts or in those unaccustomed to it, nausea and vomiting may follow. This is, sadly, occasionally used by criminally sadistic parents as a means of abusing their children, favored specifically because it doesn't leave any lasting marks, which I found upsetting when I read it. (Details for those who wish to be outraged and possibly sickened in footnote 2.) Skin irritation varies wildly from individual to individual, but is worst on skin which is already damaged or naturally thin (abraded, physically burned, open wounds, mucous membranes). Repeated occupational exposure can also result in extremely painful burning sensations. The smoke from burning Capsicum annuum plants may also irritate the respiratory tract. Getting juice in the eyes is very painful, as you'd expect. None of this really appears to constitute toxicity as the word is normally understood, and one assumes that children and pets would need, at most, exactly one experience with this to understand that this is a plant best left alone, so even though it has the potential to harm, I consider it more or less a safe plant. Though it's not often grown as a houseplant anyway.

NOID Chrysanthemum.

Chrysanthemum spp. (mum) The flowers may be toxic by ingestion, though neither Handbook nor Toxicity said they were. The main problem with Chrysanthemum spp. is that the flowers in particular, and to a lesser degree the leaves and stems, cause skin irritation in susceptible individuals. Which is all either book wanted to talk about. I would be wary of this one around kids and especially pets; while I doubt it kills, it does contain compounds similar to those in Hedera spp., q.v., and plus it just seems a little shifty.
Cissus quadrangularis As I noted in the profile for this plant, this is eaten on purpose by some people, though I get the impression that the amounts tend to be small. The only advice I could locate about preparing it was that one should not chew it, which suggests that it probably won't kill you, but it's probably painful or irritating to the mouth or digestive tract or whatever. Probably safe around kids and pets, though I'd hedge my bets and put it upon a high shelf somewhere anyway.
Citrus spp. (lemon, lime, orange) Rare allergic reactions have been reported, but the bigger danger is from the thorns on some varieties. The ASPCA website lists Citrus spp. as causing vomiting and diarrhea in both cats and dogs; I'm not sure if I think this is meaningful information or not, since almost everything in the world causes vomiting and diarrhea in cats and dogs.
Codiaeum variegatum (croton) Causes allergic skin irritation for some people, though repeated exposure appears to be necessary before that will start, and it doesn't appear to be especially serious when it does happen. Ingestion is supposed to cause a burning sensation, but that's as detailed as anybody gets. I'm not so much worried about this one.

Cryptanthus 'Elaine?' It's for sure a Cryptanthus, at least.

Cryptanthus spp. (earth star) Bromeliads are generally safe, though some Cryptanthus spp. have sharp points on the leaf edges. So it's probably not fun to swallow, but I'm guessing you could probably eat it anyway. Though, you know, don't.
Cuphea ignea (cigar flower) Some Cuphea species irritate the skin. C. ignea is not really known to be one of them, but Toxicity felt like warning everybody anyway. Draw your own conclusions.
Dahlia spp. Dahlias are generally considered safe, though they occasionally cause skin irritation, especially for those employed in handling the tubers. I wouldn't worry much about these w/r/t kids and pets.

Dizygotheca elegantissima.

Dizygotheca elegantissima (more correctly Schefflera elegantissima; false aralia) I did not find any evidence that Dizygotheca elegantissima is toxic; however, given its reassignment to the genus Schefflera, one should keep in mind that it may also contain calcium oxalate crystals and skin sensitizers like Schefflera actinophylla, q.v., and S. arboricola, and might be capable of causing pain and swelling if chewed, or causing skin reactions if handled a lot.
Euphorbia pulcherrima (poinsettia) Will be covered in Appendix 1, in a couple days.
Ficus benjamina (weeping fig, "ficus tree") Ficus spp. are more or less safe for most people in most circumstances, though I have heard of people developing asthma, wheezing, and similar respiratory problems around them, and I personally get itchy when I have to pick dead leaves out of them or whatever, which suggests I might be slightly allergic. If I am slightly allergic, then I'm just being normal: allergies to Ficus, and Ficus benjamina in particular, are pretty common among greenhouse workers, florists, etc. Aside from allergies and skin or eye irritation, Ficus spp. are pretty safe.
Ficus maclellandii (long-leaf fig, alii fig, 'Alii,' 'Alli,' 'Amstel King') As for Ficus benjamina, q.v.
Ficus microcarpa / nitida / retusa (Indian laurel) As for Ficus benjamina, q.v.
Ficus pumila (creeping fig) As for Ficus benjamina, q.v.
Kalanchoe spp. including K. blossfeldiana (flaming katy, kalanchoe, calandiva), Bryophyllum daigremontianum (mother of thousands, devil's backbone3), K. beharensis (feltbush) These do contain toxins, and in their native South Africa, they have been responsible for killing grazing animals, but for all their popularity as houseplants, there are "no cases" (says Toxicity) of Kalanchoe spp. causing poisoning by ingestion. Allergic reactions are known, but don't appear to be severe. Toxicity recommends that Kalanchoe spp. "be considered of slight or no toxicological significance." So I do.
Neoregelia cvv. Bromeliads are safe under most circumstances and to most species; however, many Neoregelia spp. have spines on the edges of the leaves, like Cryptanthus spp., which could in theory cause injury if swallowed.

Pelargonium x hortorum [something-something] 'Rose.'

Pelargonium x hortorum (geranium) Some people are sensitive to a few specific compounds in geranium essential oil, and occasionally people develop skin irritation or an actual allergy. They don't appear to be otherwise toxic, though, and should be considered basically safe plants around children and pets.
Sedum morganianum (burro's tail), S.rubrotinctum (jellybean plant), other Sedum spp. (stonecrop) Not a lot of information about these, but what there is suggests that they irritate some people's skin. Reports of toxic reactions are very rare, and usually there are no symptoms. Likely okay around children and pets, including reptiles and amphibians.
Sempervivum spp. (hen and chicks, houseleek, stonecrop) As for Sedum spp., q.v.

Solenostemon scutellarioides 'Rainbow Mix.'

Solenostemon scutellarioides (coleus, flame nettle) Cause allergic reactions in some people, and occasional non-allergic skin irritation. The later is more common in people who handle them a lot occupationally, though both reactions are rare. It appears to be safe if ingested.
Tradescantia pallida (purple heart, purple queen) A small percentage of people will develop skin irritation from handling them but this is of minimal consequence. Tradescantia spp. are one of the most commonly called-about plants for poison control centers, and are generally regarded as nontoxic for all species.
Tradescantia spathacea (Moses in the cradle, oyster plant) As for Tradescantia pallida, q.v.
Tradescantia zebrina (wandering Jew) As for Tradescantia pallida, q.v.

Yucca guatemalensis. These are an oddball variety I've had for something like ten or eleven years. It has gray variegation and is totally awesome. Variegated Yucca guatemalensis rule.

Yucca guatemalensis (spineless yucca) Neither Handbook nor Toxicity mentions Yucca guatemalensis. I did see a mention somewhere that ingestion causes vomiting and diarrhea in cats and dogs, but cat-and-dog digestive systems are obviously on a vomiting-and-diarrhea hair trigger anyway; I haven't seen anything about any other animal being poisoned by Y. guatemalensis. Flowers are incredibly unlikely indoors, but if some should form, they are said to be edible. The leaf tips, though spineless, do pose a slight mechanical danger, as do the serrated edges of the leaves: Lynn P. Griffith, Jr., author of the tropical plants growers' guide I like so much (see the sidebar), claims to have poked out an eardrum by bumping into the tip of a Yucca leaf.

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Photo credits: All are my own.

1 Do we still hate her? She hasn't gone and done anything noble or selfless that I need to know about, has she?
2 From Toxicity of Houseplants again: "Three children, ages 3, 5, and 7 were disciplined by their parents by placing a split jalapeno pepper in their mouths and setting a timer for 15 to 20 min. If the pepper was spit out, the child vomited [!], or swallowed the pepper, another pepper was placed, and another 20 min was started. The children experienced burning of the mouth, throat, and stomach, and burning of the anus when passing stool. The children cried at night from residual pain. [alarmed look] Vomiting and diarrhea were also seen as a result of the treatment. School authorities discovered the abuse, authorities were notified, and the treatments discontinued." [Hopefully because the parents had been torn to pieces by an angry mob, arrested, jailed, and torn to pieces again by angry prisoners, but the account stops there so I don't know. The ability of human beings to invent new ways of being horrible to one another should stop surprising me at some point, you'd think, but apparently not yet.] (Toxicity of Houseplants references Tominack, R. L. and Spyker, D. A., Capsicum and capsaicin -- a review: case report of the use of hot peppers in child abuse, Clin. Toxicol., 25, 591, 1987.)
3 (Included here because B. daigremontianum was at one time included in the Kalanchoe genus under the name Kalanchoe daigremontiana.) Also, it annoys me to an unreasonable degree that "devil's backbone" is apparently an acceptable common name for Bryophyllum daigremontianum, despite it having no backboney characteristics whatsoever, as far as I'm aware. Though it does have some devilish tendencies, I admit. Pedilanthus tithymaloides deserves the name a lot more, and is a better plant.