A Cautionary Tale

I knew it was bound to happen sooner or later. I've tried, of course, to be conscientious about hand-washing and so forth, but as many Euphorbias as I have, and as long as I've had them, I was going to get Euphorbia sap in the eye eventually. So here's my report about that.

What happened: On Wednesday night, our weather forecast predicted a low of 58F/14C, which was probably warm enough that I didn't need to do anything -- the plants are all either right next to the house or right next to the garage, they're packed fairly close together, and most are sitting on or near a good-sized slab of concrete. So they're in a relatively warm microclimate to begin with, warm enough that 58F/14C shouldn't be that big of a deal.

But I decided to move the ones that were easiest to move anyway, because an extra layer of protection couldn't hurt. So I intended to wheel the sets of plants that are on carts into the garage. (A couple big plants also had to be moved before I could move the ones on carts, but that's not really relevant to the story.)

One of the carts had a Euphorbia lactea next to a Euphorbia tirucalli 'Firesticks.' I'd been keeping them outside because I've been stupidly hoping that being outside would do something to clear up their fungus problem -- which is still going on, and has been going on for at least a year now.

Back row, L-R: Euphorbia milii, Pachypodium lamerei, Pilosocereus pachycladus. Front row: Euphorbia tirucalli 'Firesticks,' Euphorbia lactea, Euphorbia milii.
I'm not sure what's going on with the E. lactea: it's gotten wobbly in the pot. Kept falling over into the E. tirucalli, as I rolled the cart over the rough surface of the concrete. So I kept picking it up again. I noticed that the lactea thorns were stabbing the tirucalli stems here and there, but this isn't the first time that's happened, and I didn't think it was terribly significant. I tried to keep my hands out of the little pinpricks of sap, and pressed forward, because it was already 8:30 PM and I had other stuff I was hoping to get to before bed.

Got everything in the garage, rolled the door down, turned out the light, went in the house, and sat down at the computer to do stuff. Got about half an hour into that when I absent-mindedly rubbed my left eye.

What it was like: Initially, it just felt like there was something in my eye; it was irritating, but not unusually so. So I rubbed harder, to get whatever it was out of my eye. As you do. And that didn't make things any better, so I got up and went to the bathroom to rinse it out in the sink. And that's roughly the point when I realized that this was no ordinary foreign-object-in-the-eye situation.

For one thing, it felt hot. And it was much more irritated, much faster, than if I'd just gotten a piece of dirt in my eye. I could still see through the eye fine. I found the husband and asked him to look at the eye in question and tell me if he could see anything in there; he couldn't. And that's about the point when I thought of the Euphorbia tirucalli I'd just moved, and put things together.

(So how was the pain? Once when I was about 19, I angrily opened a heavy wooden door, while barefoot, so it swung directly into my big toe, not only stubbing it but also ripping off the toenail. It hurt about that much: bad enough that it took some concentration to think about anything else, but not so bad that I completely lost control of my faculties. This, remember, is from what was probably a single pinprick of dried sap, though. Having experienced that much, I can totally believe that getting a squirt of sap directly to the eye would be completely incapacitating, and probably would involve a good bit of writhing on the floor and/or incoherent screaming.)

So. What you're supposed to do for Euphorbia tirucalli sap is, you're supposed to run cold, clean water on the affected eye(s) for 15 minutes, seek medical attention, and then (optionally) run water on the affected eye(s) for another 15 minutes. I didn't do that.

Why didn't you do that? I didn't do that because, although it felt considerably better with the water on it, and almost immediately so, even, I was having a difficult time keeping my eye open while running water on it, because . . . I don't know. I may have an overactive blink reflex, or something. It should also be noted that what my right eye was doing while this was going on was, it was getting to look at the inside of the kitchen sink. Which is not that interesting, so it's not like the time was passing quickly or anything either.

So what wound up happening was, I'd run the water for like 30-60 seconds, feel better, get bored, and start getting annoyed at trying to keep my eye open when every instinct was telling me to close it. So then I'd get up, try to locate the husband, discuss the situation with him, and then eventually run off to rinse the eye again.

After hearing that keeping the eye open with the water on it was a problem, the husband proposed that maybe it would work better for me to lie down somewhere, and have him holding the water, that maybe it would be easier to relax that way. So at one point, he'd constructed this whole thing where a couple of chairs were supporting a piece of plywood that stretched into our upstairs shower, tilted slightly downward so the water wouldn't run all over into the bathroom. When tried, that turned out to be considerably worse (cold water all over my back and scalp, a gazillion little jets of water spraying all over my face -- generally much, much closer to waterboarding than I felt comfortable with), so we abandoned that and I went back to the kitchen sink again.

Why didn't you just seek medical attention? Well, we did consider it. Since it was 9 PM or later through this whole ordeal, though, that would have meant going to the emergency room in Iowa City, which is a significant amount of time to spend in the car without any water to run over the eye, plus time spent parking, waiting in the waiting room to see a doctor, explaining the situation, and etc. At this point, I was having to go back to the sink every 3-5 minutes, so that didn't seem workable, plus the last time I went to the emergency room, it was also for something eye-related, and I didn't want the U of I Hospital people to be thinking that I was some kind of eye hypochondriac.

More seriously, though -- there was really no indication that the hospital would have been able to do anything much for me that I couldn't do for myself at home. I wasn't in unbearable pain, I was still more or less able to think, and there's not actually a cure for E. tirucalli sap in the eye anyway, as far as I could find on-line: basically you just flush it with water in the hopes that the sap will wash out (and because keeping the eye cool dulls the pain), and wait to see how bad it's going to be. And we had running water here already. So.

Resolution: At about 9:30 or 10 PM, I took an ibuprofen, because why not, and some benadryl (diphenhydramine), because somebody on-line had said that antihistamines were sometimes helpful. By about 10:30 PM, things had improved to the point where I was able to lie on the couch and watch TV ("It's Always Sunny in Philadelphia") for a while without pain. Don't know if the drugs and the feeling better were related or not, but I suppose it doesn't matter.

Wound up going to bed at about 1 AM, and slept in until 11 AM. I don't know if the sleeping in is related or not either, but that's almost unheard of for me: I rarely sleep in later than 9:30 AM.

It's possible that my left eye is a little more prone to watering since this, but it's also possible that I'm just paying more attention to it. No lingering effects that are at all life-disrupting, anyway -- no pain, no problems seeing, no scarring.

What next? Damned if I know. I've had at least one E. tirucalli at all times since 2001, and this is the first time anything like this has happened. If I don't have to worry about it happening again until 2025, that's not so terrible.

On the other hand, the whole Euphorbia genus has made itself awfully annoying over the last year or so, with the ineradicable fungus problem, and there have been several occasions when I've been very tempted to just throw out all the affected plants¹ and start over. Or maybe not start over, even, since I don't know how to rid the house of the fungus. Also, this was likely just a tiny pinprick of sap. Next time it might not be.

A new thing they've come up with to annoy me: this branch just up and turned brown and died after it spent some time outside. Dunno why. But Euphorbia pseudocactus is on my list too.
Maybe I'm just done with Euphorbias. I'm certainly going to be thinking about it pretty seriously.

-

¹ Euphorbia tirucalli, E. tirucalli 'Firesticks,' E. drupifera (deceased), E. milii, E. milii 'Candyland' (deceased), E. milii large hybrid, Pedilanthus tithymaloides, P. 'Jurassic Park 2,' P. 'Silver Star,' Synadenium grantii, S. grantii var. rubrum, E. bougheyi variegata, E. lactea, E. trigona, E. trigona 'Red,' and E. pseudocactus.
All of these are officially Euphorbias at the moment, even if I've written their names as Pedilanthus or Synadenium.

More corrections

Readers have alerted me to two more errors on PATSP, having to do with one of the profile posts and one misidentified plant. Then I ran into another thing all on my own, where something in one of the profiles needed a bit of clarification. So here we are again.

1. Ficus elastica and isoprene

In the Ficus elastica profile, I sort of implied that the people making natural rubber extract isoprene from the sap of Hevea brasiliensis and other plants, then polymerize it into natural rubber. This is not the case.

Model of isoprene. Black balls are carbon atoms, white are hydrogen, and the gray connectors represent pairs of electrons. This is my own photo: I would have used it in the Ficus elastica profile, except that I'd forgotten I owned a molecular model set.¹
Straight-up, pure isoprene can and does exist. It's a colorless, low-boiling liquid which is mostly obtained either as a byproduct of oil and naphtha refining, or by heating natural rubber until it starts disintegrating into smaller molecules. The isoprene so obtained can then be polymerized into a substance with properties very close to natural rubber.² Readers who collect oxymorons will be pleased to know that the term for this artificially polymerized, artificially obtained polyisoprene is "synthetic natural rubber."

However. Natural natural rubber polymerizes within the plant, forming small globs of polyisoprene that float around in the sap. When the sap is collected from the plant, these globs are then coagulated, washed, filtered, pressed, and stretched to form blocks of rubber. So it's still technically correct of me to say that isoprene is polymerized to form natural rubber, but the polymerization has already happened by the time the sap is collected.³

2. Persea americana toxicity

Next up, in the Persea americana profile, I devoted footnote 2 to the toxicity of the plant, saying that all parts of the plant except the fruit should be considered toxic, particularly to pets. Then Poor Richard's Almanac had to go and spoil that one for me by writing a post about the culinary use of avocado leaves.

My Persea americana, as of yesterday morning. I had two plants to begin with, and planted them together in this pot to try to make it fuller. That's mostly worked, but the two plants together seem to dry out a lot faster than they did when separated, so there have been more dropped leaves and
This sent me deep into the bowels of the internet to do research. I won't bore you with all the twists and turns, but the gist is:

Yes, people really do cook with avocado leaves.

No, not any avocado leaf will do: the variety used in Mexican cooking is a specific race of the avocado (according to some sources it's a separate species, Persea drymifolia, but others consider it just a race of P. americana).

Avocado leaves should still be considered toxic to all pets, especially especially especially to birds: ALLLLLLLLLLLL the bird-toxicity lists say Persea fruit or foliage is potentially lethal for at least some species of bird, and they say this over and over again, in extremely shrill and insistent language.

Humans don't seem to be as affected by the toxin in avocado leaves as animals are, and animals aren't all affected to the same degree. Wikipedia's article on persin, the actual toxic agent in Persea americana leaves,⁴ reports that consumption of avocado leaves produces a wide array of unpleasantness in a whole barnyard full of animals (cats, dogs, rabbits, birds, mice, cows, goats, horses, pigs, sheep, ostriches, chickens, turkeys and fish), ranging from reduced milk production all the way up to asphyxia and death. (Wikipedia's original source is a bit more detailed, q.v.)

The way to tell whether you have one of the cooking-type avocado leaves or the useless and/or poisonous avocado leaves: leaves which are okay to cook with will smell like anise, and the fruits will have much thinner skin. Generally, if you start an avocado plant from a supermarket fruit's seed, you're not going to end up with leaves you can cook with.

So I was partly wrong: a subset of avocado plants have leaves which are not toxic, at least not in the small quantities needed to flavor food. (I don't recommend sitting down and eating ten leaves in one sitting, even if it is the drymifolia variety.) In the context of a houseplant that was started from a supermarket avocado, though, you're better off treating it as toxic. Even if it doesn't hurt you, it's not likely to do anything for your food.

3. Aloe aristata isn't Aloe aristata

Finally, I've found out from Taylor Holzer (a reader) that I've been calling the below plant Aloe aristata when it is in fact a hybrid of Aloe aristata and something else.

My Aloe aristata x whatever, in January 2011.
The most likely candidate, I think, is Gasteria batesiana, which cross is called Gasteraloe x beguinii, but a similar hybrid is formed by A. aristata and A. variegata, and I'll probably never know for sure which cross I have.

A. aristata is apparently distinguishable by the dead tips on the ends of the leaves, and the thinner, less fleshy leaves. (I'd thought that maybe the differences just depended on cultural conditions -- since I'm not growing them outdoors, a lot of my plants don't look quite like they ought to. But sadly, no.) It's also reluctant to offset, is the rumor, whereas my plant offsets more or less constantly. My guesses about the actual ancestry are based both on Holzer's own guesses and on this discussion thread at davesgarden.com.

Aloe aristata hybrid (L), Aloe aristata species (R). Photo credit: Taylor Holzer. Used by permission.
I will go through the blog and change the name at some point, but I just finished a few rounds of name-changing, and am pretty sick of it, so it might take me a while. (It's bad enough that I have to go change two profiles.) Since some of you got offsets of this plant from me, though, I figured I should let you know that it was half-misidentified.

-

Photo credits: Mine except where noted.

¹ Yes, I am that nerdy. In fact, it's actually quite a bit worse than you think, because I don't just have a molecular model set, I have six, which were purchased between my senior year of high school and my sophomore year of college. (The first one, in high school, was I think actually a birthday or Christmas present from Mom and Dad, but I think I bought the other five. It's been a while; some of the details are fuzzy.) So I can model anything up to about 80 carbon atoms. Here is a short segment of a natural rubber (cis-polyisoprene) molecule, for example:


² It's not exactly the same as natural rubber because natural rubber contains impurities from the original sap: fatty acids, proteins, inorganic compounds ("ash"), that sort of thing.
³ (If you want to be even more technical: the plants don't polymerize isoprene, but its phosphorylated form.)
⁴ Regrettably, in the course of editing this post, I lost a "persin"/"person" pun I was very proud of. I could put it here anyway, but it was context-dependent and wouldn't be funny without the set-up. I just wanted you to know.

Houseplant Toxicity Week Appendix 2: Index

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).

Second 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 1)
This is the index for the Houseplant Toxicity Series of posts. If you have reached this page first in a Google search or whatever, I recommend that you find the plant on this list and then follow the link to get more specific information about that plant. If the plant's botanical name is highlighted, that means that it was the subject of a plant profile here at PATSP, in which case you can also click the plant's name and find out care information, trivia, and so forth.
Toxicity ratings are more or less decided as follows:
Crazy super dangerous: is highly toxic, and has either resulted in repeated human or pet fatalities, or is for whatever reason thought to be very likely to do so.
Dangerous : Fatalities are rare or nonexistent, but the plant is still capable of causing serious and possibly permanent injury requiring hospitalization, extreme pain, temporary disability, or something along those lines. Dangerous plants may make you want to die, but you probably won't actually die. Though the possibility is theoretically there.
Potentially dangerous: This designation is for plants which are probably capable of causing harm and maybe even death, but you'd have to eat your body weight in the plant for that to happen, or it's impossible to find any actual case reports, or etc. Potentially dangerous plants will probably be more risky for pets than people.
Unpleasant : The plant is not likely to kill you, or even to result in serious injury, but it may be capable of causing vomiting, bad skin or eye irritation, diarrhea, burning, itching, or other bad things, and you don't want to eat it on purpose. This is also the designation for plants which are otherwise safe but bear thorns or spines that could puncture the mouth or digestive tract.
Safe : Should be safe in most quantities and for most people/animals, though exceptions may exist.
Unknown : I couldn't find enough good information to decide one way or the other, or I found the information but it conflicted with other information. I did make a guess as to the level of risk on the page for unknown-toxicity plants, but this is only a (semi-educated) guess and I am almost certainly really wrong on one or more of the plants therein.
I know the formatting on this page needs some work (EDIT: Some of the problem is that Google changed how Blogger pages are formatted in the spring of 2012.), and that it's hard to read as it stands. I did the best I could. Putting together a draft of this index took me a good three hours to begin with; I didn't really have the patience to spend time fiddling with the formatting too.
Abutilon hybridum (flowering maple) [Unpleasant – link]
Acalypha hispida (chenille plant) [Unpleasant – link]
Acalypha reptans (dwarf chenille plant) [Unpleasant – link]
Adenium obesum (desert rose, mock azalea) [Crazy super dangerous – link]
Adiantum spp. (maidenhair fern) [Unknown – link]
Adromischus spp. [Potentially dangerous – link]
Aechmea fasciata (silver vase plant) [Safe – link]
Aeschynanthus lobbianus (lipstick plant) [Safe – link]
Aeschynanthus speciosus (goldfish plant) [Safe – link]
Agapanthus orientalis (blue African lily) [Potentially dangerous – link]
Agave spp. (century plant) (A. victoriae-reginae) [Dangerous – link]
Aglaonema spp. (Chinese evergreen) [Potentially dangerous – link]
Albuca bracteata (pregnant onion) [Dangerous – link]
Allamanda cathartica [Potentially dangerous – link]
Aloe spp. including A. vera (medicinal aloe) Alworthia 'Black Gem' [Potentially dangerous – link]
Alpinia zerumbet (shell ginger, variegated ginger) [Unpleasant – link]
Alternanthera spp. (A. dentata 'Purple Knight') [Safe – link]
Amaryllis spp. (amaryllis) [Dangerous – link]
Ananas comosus (pineapple) [Unpleasant – link]
Anthurium spp. including A. andraeanum (flamingo flower, oilcloth flower, tailflower) and the various hybrids (bird's-nest anthurium, e.g.) [Potentially dangerous – link]
Aphelandra squarrosa (zebra plant, saffron spike) [Safe – link]
Araucaria bidwillii (bunya-bunya) [Unpleasant – link]
Araucaria heterophylla (Norfolk Island pine) [Unpleasant – link]
Ardisia crenata (coral berry) [Unknown – link]
Ardisia elliptica (shoebutton tree) [Unknown – link]
Asparagus spp. (asparagus ferns) [Potentially dangerous – link]
Aspidistra lurida, A. elatior (cast-iron plant) [Unknown – link]
Asplenium nidus, A. antiquum (birdsnest fern, Japanese birdsnest fern) [Unknown – link]
Asplundia 'Jungle Drum' [Unknown – link]
Aucuba japonica (Japanese laurel, spotted laurel) [Potentially dangerous – link]
Beaucarnea recurvata (ponytail palm) [Safe – link]
Begonia spp. (wax begonia, tuberous begonia, rex begonia) [Safe – link]
Bougainvillea spp. (bougainvillea) [Unpleasant – link]
Bowiea volubilis (climbing onion) [Dangerous – link]
Brassolaeliocattleya cvv. [Safe – link]
Brugmansia spp. (angel's trumpets, tree datura) [Crazy super dangerous – link]
Caladium cvv. (angel wings, heart of Jesus, elephant's ear) [Potentially dangerous – link]
Calathea spp. including Calathea ornata [Safe – link]
Capsicum annuum (chili pepper, bell pepper, etc.) [Unpleasant – link]
Caryota mitis and other Caryota spp. (fishtail palm) [Potentially dangerous – link]
Cattleya spp. [Safe – link]
Cereus peruvianus [Unknown – link]
Ceropegia woodii (rosary vine, string of hearts) [Unknown – link]
Cestrum diurnum (day-blooming jessamine, day-blooming cestrum) [Potentially dangerous – link]
Cestrum nocturnum (night-blooming jasmine, night-blooming jessamine) [Dangerous – link]
Chamaedorea elegans (parlor palm) [Safe – link]
Chamaedorea metallica (metallica palm, miniature fishtail palm) [Safe – link]
Chamedorea seifrizii (bamboo palm) [Safe – link]
Chlorophytum comosum (spider plant, airplane plant, mala madre) [Unknown – link]
Chlorophytum x 'Fire Flash' (Fire Flash, mandarin plant, green orange) [Unknown – link]
Chrysalidocarpus lutescens (areca palm) [Safe – link]
Chrysanthemum spp. (mum) [Unpleasant – link]
Cissus quadrangularis [Unpleasant – link]
Cissus rhombifolia (grape ivy, oakleaf ivy) [Safe – link]
Citrus spp. (lemon, lime, orange) [Safe – link]
Clivia miniata (kaffir lily) [Potentially dangerous – link]
Codiaeum variegatum (croton) [Unpleasant – link]
Coffea arabica (coffee tree) [Safe – link]
Colocasia spp. (elephant ear, taro) [Crazy super dangerous – link]
Columnea spp. [Safe – link]
Cordyline fruticosa (ti plant) [Safe – link]
Cotelydon spp. [Potentially dangerous – link]
Crassula ovata (jade plant) [Dangerous – link]
Cryptanthus spp. (earth star) [Unpleasant – link]
Cryptostegia madagascariensis (Madagascar rubber vine) [Dangerous – link]
Ctenanthe spp. (never-never plant) [Safe – link]
Cuphea ignea (cigar flower) [Unpleasant – link]
Cycas revoluta and other Cycas spp. (sago palm) [Dangerous – link]
Cyclamen persicum (cyclamen) [Potentially dangerous – link]
Cyrtomium falcatum (holly fern) [Unknown – link]
Dahlia spp. [Unpleasant – link]
Datura spp. (devil's trumpet, jimson weed, sacred thorn apple) [Crazy super dangerous – link]
Davallia spp. (rabbit's-foot fern) [Unknown – link]
Dendrobium spp. [Safe – link]
Dieffenbachia spp. (dumb cane) [Dangerous – link]
Dionaea muscipula (venus flytrap) [Unknown – link]
Dizygotheca elegantissima (false aralia) [Unpleasant – link]
Dracaena deremensis cvv. ('Janet Craig') ('Warneckei') [Potentially dangerous – link]
Dracaena fragrans ('Massangeana') (corn plant) [Potentially dangerous – link]
Dracaena surculosa (sometimes D. godseffiana; gold-dust dracaena) [Potentially dangerous – link]
Dracaena marginata (Madagascar dragon tree) [Potentially dangerous – link]
Dracaena sanderiana (ribbon plant, lucky bamboo) [Potentially dangerous – link]
Echeveria spp. [Unknown – link]
Ensete spp. (ornamental? banana) [Safe – link]
Epipremnum aureum (pothos, devil's ivy) [Potentially dangerous – link]
Episcia spp. (flame violet) [Safe – link]
Eucharis grandiflora (amazon lily) [Unknown – link]
Euphorbia bougheyi variegata [Dangerous – link]
Euphorbia cooperi [Dangerous – link]
Euphorbia drupifera (giraffe tree) [Dangerous – link]
Euphorbia grandicornis (cow horns) [Dangerous – link]
Euphorbia lactea (candelabra cactus, dragon bones, hat-rack cactus) [Dangerous – link]
Euphorbia milii (crown of thorns) [Dangerous – link]
Euphorbia pseudocactus [Dangerous – link]
Euphorbia pulcherrima (poinsettia) [Unpleasant – details in appendix 1]
Euphorbia tirucalli (pencil cactus) [Crazy super dangerous – link]
Euphorbia trigona (African milk bush, African milk tree) [Dangerous – link]
Exacum affine (persian violet) [Unknown – link]
Fatshedera lizei (tree ivy) [Unknown – link]
Fatsia japonica [Unknown – link]
Fenestraria rhopalophylla [Unknown – link]
Ficus benjamina (weeping fig, "ficus tree") [Unpleasant – link]
Ficus elastica (rubber plant) [Potentially dangerous – link]
Ficus lyrata (fiddle-leaf fig) [Unpleasant – link]
Ficus maclellandii (long-leaf fig, alii fig, 'Alii,' 'Alli,' 'Amstel King') [Unpleasant – link]
Ficus microcarpa / nitida / retusa (Indian laurel) [Unpleasant – link]
Ficus pumila (creeping fig) [Unpleasant – link]
Fittonia albivenis (nerve plant, mosaic plant) [Safe – link]
Fuchsia spp. [Safe – link]
Gardenia jasminoides (gardenia, cape jasmine) [Safe – link]
Gasteria spp. [Unknown – link]
Gibasis geniculata (Tahitian bridal veil) [Safe – link]
Gloriosa superba (glory lily, climbing lily, gloriosa lily) [Crazy super dangerous – link]
Grevillea robusta (silk oak) [Potentially dangerous – link]
Guzmania lingulata (scarlet star bromeliad) [Safe – link]
Gynura aurantiaca (purple passion vine, purple velvet plant) [Safe – link]
Ludisia discolor (jewel orchid) [Safe – link]
Hatiora salicornioides (drunkard's dream) [Unknown – link]
Haworthia spp. [Safe – link]
Hedera canariensis (Algerian ivy) [Dangerous – link]
Hedera helix (English ivy) [Dangerous – link]
Hemigraphis exotica (waffle plant) [Unknown – link]
Hibiscus rosa-sinensis (tropical hibiscus) [Safe – link]
Hippeastrum spp. (amaryllis) [Dangerous – link]
Homalomena cvv. ('Emerald Gem') [Potentially dangerous – link]
Hoya spp. (H. carnosa) (wax flower) [Safe – link]
Hyacinthus orientalis (hyacinth) [Potentially dangerous – link]
Hydrangea macrophylla (hydrangea) [Dangerous – link]
Hylocereus undatus (dragon fruit cactus) [Unknown – link]
Hypoestes phyllostachya (pink polka-dot plant) [Potentially dangerous – link]
Jatropha spp. (jicamilla, physic nut, bellyache bush, coral plant, etc.) [Crazy super dangerous – link]
Kalanchoe spp. (including K. beharensis, K. luciae, K. tomentosa, K. blossfeldiana, etc., as well as the former Kalanchoe now called Bryophyllum daigremontianum) [Unpleasant – link]
Lantana camara (lantana) [Crazy super dangerous – link]
Laurus nobilis (bay leaf, laurel) [Safe – link]
Ledebouria socialis (silver squill) [Dangerous – link]
Lilium longiflorum (Easter lily) [Dangerous – link]
Lithops spp. (living stones) [Safe – link]
Mandevilla spp. (Dipladenia) [Dangerous – link]
Maranta leuconeura erythroneura (prayer plant) [Safe – link]
Maranta leuconeura kerchoviana (prayer plant, rabbit tracks, ten commandments plant) [Safe – link]
Mimosa pudica (sensitive plant) [Potentially dangerous – link]
Monadenium ellenbeckii (and probably other Monadenium spp.) [Potentially dangerous – link]
Monstera deliciosa (split-leaf philodendron, swiss cheese plant) [Potentially dangerous – link]
Murraya paniculata (mock orange, orange jasmine) [Unknown – link]
Musa spp. (banana) [Safe – link]
Nandina domestica (heavenly bamboo) [Dangerous – link]
Narcissus spp. (daffodil, narcissus, paper-white) [Dangerous – link]
Nematanthus spp. (guppy plant) [Safe – link]
Neoregelia cvv. in general (by association) [Unpleasant – link]
Neoregelia 'Fireball' specifically (by association) [Safe – link]
Nephrolepis exaltata (Boston fern) [Safe – link]
Nerium oleander (oleander) [Crazy super dangerous – link]
Oncidium cvv. (by association) [Safe – link]
Ophiopogon spp. (lilyturf, Liriope) [Unknown – link]
Opuntia spp. (bunny ears cactus, prickly pear) [Potentially dangerous – link]
Ornithogalum spp. (pregnant onion, star of Bethlehem) [Dangerous – link]
Oxalis spp. (shamrock) [Potentially dangerous – link]
Pachypodium geayi / lamerei (Madagascar palm) [Dangerous – link]
Pandanus spp. (screw pine) [Potentially dangerous – link]
Paphiopedilum spp. (lady-slipper orchid) [Safe – link]
Pedilanthus tithymaloides (redbird cactus, devil's backbone) [Dangerous – link]
Pelargonium x hortorum (geranium) [Unpleasant – link]
Pellionia spp. including Pellionia pulchra [Safe – link]
Peperomia argyreia (watermelon plant) [Safe – link]
Peperomia caperata / P. griseoargentea (Emerald Ripple) [Safe – link]
Peperomia obtusifolia (baby rubber plant) [Safe – link]
Persea americana (avocado) [Potentially dangerous – link]
Phalaenopsis spp. (moth orchid) [Safe – link]
Philodendron 'Autumn' [Dangerous – link]
Philodendron bipennifolium (also P. panduraeforme; (fiddle-leaf philodendron, horse head philodendron) [Dangerous – link]
Philodendron 'Imperial Red' [Dangerous – link]
Philodendron 'Congo Green' [Dangerous – link]
Philodendron 'Congo Red' [Dangerous – link]
Philodendron gloriosum [Dangerous – link]
Philodendron hastatum [Dangerous – link]
Philodendron hederaceum (also P. oxycardium, P. cordatum, P. scandens, P. micans; velvet philodendron, heart-leaf philodendron, 'Brasil') [Dangerous – link]
Philodendron 'Moonlight' [Dangerous – link]
Philodendron 'Pink Princess' [Dangerous – link]
Philodendron 'Prince of Orange' [Dangerous – link]
Philodendron selloum (P. bipinnatifidum; tree philodendron) [Dangerous – link]
Philodendron 'Xanadu' [Dangerous – link]
Pilea cadierei (aluminum plant) [Safe – link]
Pilea depressa (baby toes) [Safe – link]
Pilea nummulariifolia (creeping Charlie) [Safe – link]
Platycerium bifurcatum and other Platycerium spp. (staghorn fern) [Unknown – link]
Plectranthus verticillatus (Swedish ivy) [Safe – link]
Plumeria spp. (frangipani) [Crazy super dangerous – link]
Podocarpus macrophyllus (buddhist pine) [Unknown – link]
Polyscias balfouriana (balfour aralia), P. crispata, P. fruticosa (ming aralia) [Potentially dangerous – link]
Primula spp. (primrose, oxlip) [Potentially dangerous – link]
Radermachera sinica (China doll) [Unknown – link]
Rhapis excelsa (lady palm) (by association) [Safe – link]
Rhododendron spp. (azalea) [Crazy super dangerous – link]
Ricinus communis (castor bean) [Crazy super dangerous – link]
Saintpaulia ionantha cvv. (African violet) [Safe – link]
Sansevieria cylindrica, other Sansevieria spp. [Potentially dangerous – link]
Sansevieria trifasciata (snake plant, mother-in-law's tongue) [Potentially dangerous – link]
Saxifraga stolonifera (strawberry begonia) [Safe – link]
Schefflera actinophylla (umbrella tree, octopus tree) [Potentially dangerous – link]
Schefflera arboricola (umbrella tree, octopus tree, arboricola) [Potentially dangerous – link]
Schlumbergera truncata cvv. (Christmas / Easter / Thanksgiving / holiday cactus) [Safe – link]
Scilla spp. (squill, star hyacinth) [Dangerous – link]
Scindapsus pictus (satin pothos) [Potentially dangerous – link]
Sedum morganianum (burro's tail) [Unpleasant – link]
Sedum rubrotinctum (jellybean plant) [Unpleasant – link]
Other Sedum spp. (stonecrop) [Unpleasant – link]
Selaginella spp. (spikemoss, resurrection plant, rainbow fern) [Unknown – link]
Sempervivum spp. (hen and chicks, houseleek, stonecrop) [Unpleasant – link]
Senecio cineraria (dusty miller) [Potentially dangerous – link]
Senecio macroglossus (cape ivy) [Potentially dangerous – link]
Senecio mikanioides (German ivy) [Potentially dangerous – link]
Senecio radicans (string of bananas) [Potentially dangerous – link]
Senecio rowleyanus (string of beads) [Potentially dangerous – link]
Senecio x hybridus (cineraria) [Potentially dangerous – link]
Sinningia speciosa (gloxinia) [Safe – link]
Solanum pseudocapsicum (Jerusalem cherry) [Dangerous – link]
Soleirolia soleirolii (baby tears) [Safe – link]
Solenostemon scutellarioides (coleus, flame nettle) [Unpleasant – link]
Spathiphyllum spp. (peace lily) [Potentially dangerous – link]
Strelitzia reginae / nicolai (bird of paradise) [Potentially dangerous – link]
Streptocarpus spp. (cape primrose) [Safe – link]
Stromanthe spp. (by association) [Safe – link]
Synadenium grantii (African milk bush, African milk tree) [Dangerous – link]
Syngonium podophyllum [Potentially dangerous – link]
Tagetes spp. (French marigold, African marigold) [Potentially dangerous – link]
Tillandsia cyanea (pink quill) [Safe – link]
Tillandsia spp. (air plants) [Safe – link]
Tolmiea menziesii (piggyback plant) [Safe – link]
Tradescantia pallida (Setcreasea purpurea; purple heart, purple queen) [Unpleasant – link]
Tradescantia spathacea (Moses in the cradle, oyster plant) [Unpleasant – link]
Tradescantia zebrina (Zebrina pendula; wandering Jew) [Unpleasant – link]
Tropaeolum majus (nasturtium) [Safe – link]
Tulipa spp. (tulip) [Potentially dangerous – link]
Tylecodon spp. [Potentially dangerous – link]
Vriesea spp. including Vriesea splendens (flaming sword bromeliad) [Safe – link]
Yucca guatemalensis (spineless yucca) [Unpleasant – link]
Zamia spp. including Z. furfuracea, Z. integrifolia, Z. pumila (coontie palm, cardboard palm) [Dangerous – link]
Zamioculcas zamiifolia (ZZ plant, fat boy, eternity plant) [Potentially dangerous – link]
Zantedeschia aethiopica (calla lily) [Dangerous – link]
Zygocactus spp. (Christmas / Easter / Thanksgiving / holiday cactus) [Safe – link]

(Partial) Bibliography (for the whole series of posts):
Nelson, Lewis S., Richard D. Shih, and Michael J. Balick. Handbook of Poisonous and Injurious Plants, 2nd ed., Springer Science + Business Media, New York, NY, 2007.
Spoerke, David G., Jr., and Susan Smolinske. Toxicity of Houseplants, CRC Press, Inc., Boca Raton, FL, 1990.
http://www.theamateursdigest.com/epoisons.htm