A Small Rant About Plant Toxicity Lists

Plant toxicity comes up a lot at work. People who are buying a plant often want to know if it's safe for dogs, cats, birds, children, or what have you, and this is something that houseplant books are surprisingly reluctant to cover.

We do have a (cat-specific) list at work, up at the front counter, and I refer to it sometimes, but it's not entirely accurate (it lists Sansevieria trifasciata as safe, when it is not) and is really horribly incomplete.

Sansevieria trifasciata 'Moonglow' or 'Moonshine' (which are possibly the same plant under different names). This species can be lethal to cats.
So I've been trying for some time now to do the research and come up with some kind of actual, useful list to make a blog post about, and/or use at work instead of the list we've got, and this has been frustrating. There will still be a list, eventually: I'm trying as hard as I can. But here's why it's taking longer than it should to come up with:

1. The lists do not agree with one another. One list has a plant as safe, the next list will say it's poisonous. Sometimes this is resolvable, sometimes it's not.

2. The lists are usually very short. It's a rare one that has more than about fifty names on it: there are more than fifty species of plant in the room I'm sitting in right now. So they're extremely limited, and many plants aren't on any list, period.

3. They give almost no indication of how dangerous a plant actually is. Tradescantia zebrina, which plant might, at worst, make your cat throw up or irritate your baby's skin, is sitting there on the same "unsafe" list as Adenium obesum and Nerium oleander, either of which could take down your whole family reuinion. Nerium and Tradescantia are clearly not equivalent safety risks, and yet the lists almost never indicate that some plants are more dangerous than others.

Tradescantia zebrina.

4. There's a lot of guilt by association. Dieffenbachia spp. contain calcium oxalate crystals. Dieffenbachia spp. are ridiculously dangerous. Spathiphyllum spp. also contain calcium oxalate crystals. Therefore Spathiphyllum spp. must also be ridiculously dangerous. Except -- no. As far as I've been able to find in firsthand accounts or in the medical literature, Spathiphyllum spp., if eaten, might make your mouth burn and hurt, but there don't seem to be any actual cases of someone being killed or seriously injured by one. The calcium oxalate crystals, while unpleasant, are clearly not the whole story. This is not to say that association is never useful: it's a pretty reasonable bet that if Maranta leuconeura erythroneura is safe, and Calathea ornata is safe, then Stromanthe sanguinea, which is also in the family Marantaceae, is going to be safe too. But do you want to bet somebody's life on that?

5. The names. Oh, gods, the names. Looking around at the existing on-line lists, I have found:

a. Names which are merely misspelled but otherwise clear ("buddist pine," "cineria"),
b. Common and botanical name mismatches ("aralia -- Dizygotheca elegantissima"),
c. Names which are so vague as to be completely useless ("evergreen"),
d. Names which refer to more than one plant at once -- a common enough pitfall of common names anyway ("zebra plant"),
e. Cultivar names being presented as common names ("Florida Beauty"),
f. Cultivar names that refer to more than one species (If "Florida Beauty" is on the list, then does that mean that Philodendron 'Florida Beauty' is toxic, or that Dracaena surculosa 'Florida Beauty' is? Or are they both? Or are we talking about some other "Florida Beauty," perhaps Caladium 'Florida Beauty?'),
g. Names which are fragmentary ("elaine," "cordatum"),
h. Names which are obscure ("monkey plant" -- or is that a typo for "money plant?" And if it's a typo, which "money plant" are they talking about?),
i. And names which are just plain wrong ("dracaena palm," "lily spider").

Philodendron hederaceum, the plant most likely being referred to as "cordatum," above.

6. And then even the most conscientious of sites will usually make no distinction among the possible victims: either it's poisonous to everything: cats, dogs, people, birds, fish, snakes, and lizards, or it's safe for everything. The odds are good that some plants are toxic to reptiles but not mammals, or toxic to cats but not anything else. None of the lists acknowledge this.

So here's the rant part, specifically for the medical, veterinary, and pet-enthusiast communities:

If you're going to put one of these toxic/non-toxic lists on your website, I beg you to please go to the trouble to, you know, make sure that your lists refer to actual plants. It's not good enough to throw names together at random without differentiating between botanical, common, and cultivar names, or worse yet, putting botanical, common and cultivar names together in new combinations. If you do this, you're making the toxic-plant situation more confusing, and therefore worse.¹ If I can't figure out whether Begonias are dangerous or not, given weeks to look at all the on-line lists and the relatively low stakes of having no actual pets or children to worry about, how in the hell do you expect people who do have pets or children to be able to figure it out? Should they just go with whatever website comes up first in the Google search? Flip a coin?

It'd also be nice, in light of the variability of common names,² if someone would include some pictures with these lists. I may not know "aluminum plant," and I may not know Pilea cadierei, but if one of these is in my house, I'd recognize it:


I will continue to try to piece together a usable list from other lists, anecdotes, inference, and guilt-by-association, but don't count on said list being available anytime very soon. I've been working on it for months already, and have not actually answered most of the questions I set out to answer. So it's slow. Don't hold your breath.

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¹ As far as it goes, this is a really good argument for why houseplant owners should make the effort to learn the botanical names for their plants. You don't have to be able to pronounce it, you don't need to be able to spell it, but at the very least you should be able to recognize it if you see it, or know what letters it starts with, or something. Can you imagine calling Poison Control, thinking your pet or child is dying in front of your eyes, and not being able to call the plant s/he just ate anything more specific than "tropical foliage?" Or (to bring back my favorite example) "zebra plant?" ("Okay, sir/ma'am, calm down. Can you tell me which zebra plant you're talking about? There are eleven by that name in the book here.")
² I know someone who had a plant she calls "Polish plant" because it came from a relative originally, and the relative believed that it was from Poland. This was the common name within the family, but of course nobody who wasn't in the family would have known what "Polish plant" was, or had any way to find out. Also the plant turned out to be a Pandanus veitchii, and they're not Polish at all. Not even close, really: veitchii is from Madagascar. (Wikiposedly, anyway.)