Euphorbia tirucalli was originally supposed to go with the Wizard of Oz series of profiles (I intended it for Scarecrow, which eventually went to Cryptanthus spp.), but as I got further into the research, it seemed less and less appropriate for any of the characters there, and more and more X-Filesy. So it was postponed, and now here we are. (I don't have any plans to do an X-Files series.1)
To look at it, you wouldn't think this was a plant with a plan. New branches seem to arise from any old spot and head out in any old direction, and this is especially noticeable on smaller, younger plants. The net effect, especially once you factor in the tiny, pointless leaves that appear and disappear on the plant, is of a plant that doesn't know what it's doing, that has no organizational ability at all.2 Older plants have the same tendencies, though on bigger plants (given time, they can get to be 39 feet / 12 meters tall!), the randomness tends to cancel itself out somewhat. Even then, though, they may need occasional pruning back to maintain an attractive shape.
Alas, it's all a trick, a conspiracy if you will. It's actually quite a clever plant, considering. It's good at thinking on its feet, for example: E. tirucalli has been taken from its native South and East Africa and introduced pretty much anywhere in the world that's fairly dry and doesn't freeze, where it has occasionally been so successful that it's made a nuisance of itself. It's also deceptively well-defended. Virtually all Euphorbia species have cactus-like thorns for defense, but E. tirucalli is one of the thornless exceptions. It has instead cranked up the other Euphorbia defense mechanism to eleven, and gone for exceptionally poisonous, nasty sap.
Horror stories about the sap abound on the internet. The sap can cause painful, temporary blindness3 if it gets in eyes (even just rubbing your eyes is dangerous, if sap has dripped on your hands), and some people blister and burn from skin contact too, though usually the skin irritation takes a day or so to show up. Not content just to cause pain and blindness, the plant has long-term ideas as well: it contains phorbol esters, which are not only skin irritants but actually promote cancer development, suppress the immune system, and activate dormant Epstein-Barr virus.4
So naturally, because it's unpleasant and dangerous, 1) humans are interested in producing much, much more of it, and 2) it's sold by the deluded or unscrupulous as a "natural cancer cure."
Let's start with the production.
The sap is interesting for a lot of other reasons. Rubber (a very low-quality rubber, but still5) can be made from it. It's also apparently fairly easy to treat the sap to create a gasoline-like substance, which is the main reason we may be seeing it heavily cultivated in the future.6 (Another reason is that it can grow on land which is unsuitable for food crops, and in areas which get little rainfall: it may not be much, but any way to get useless land to produce something useful is progress, kinda.) In favorable conditions, cuttings can grow from 5 cm (2 in) to 50 cm (19.5 in) in a single growing season, it doesn't seem to be affected by any pests, and plants can be cut down to the ground and will still easily regrow, meaning that replanting wouldn't have to be done often. The obvious disadvantages: the raw sap is sticky, so it seems like it would be difficult to process (but then, I guess they process pine trees just fine, don't they?), and the raw sap is dangerous, which means that worker safety might be a bit of a hurdle, especially when you consider that these are mostly going to be grown in hot climates, where it's not especially safe to cover someone with a hazmat suit for protection.
The plant is used "medicinally" around the world too, to "cure" cancer, warts, asthma, cough, earache, assorted kinds of pain, rheumatism, to cauterize wounds, colic, leprosy, paralysis, bone fractures, impotence, thorn extraction, and finally one use that I personally shudder to even contemplate -- hemorrhoids. (Even longer list here.) I also found one account of a person who says his nearsightedness was slightly improved after contact with E. tirucalli sap, though please don't try this yourself. (Or, if you do, don't credit or blame me for whatever happens: I want nothing whatsoever to do with your experiment.)
For a long time, the incidence of two particular rare cancers in Africa has been a puzzle: Burkitt's lymphoma is a malignant non-Hodgkins lymphoma, and nasopharyngeal carcinoma is a cancer of the, um, the nasopharynx, which is, in layman's terms, sort of where the pathway down to the throat meets the pathway forward to the nose, above and behind the soft palate. It's a weird little spot, but it can get cancer.7 Both of these also seem to be related to Epstein-Barr infection, and although cases can be found anywhere, there do seem to be more cases of these cancers in parts of East Asia (which is thought to be related to diet8) and Africa. The African version is more likely to strike children, is found more often at low altitudes, and is also incredibly gross (pics at Wikipedia, but remember, I warned you).
The thinking at the moment seems to be that malarial infection (which primarily occurs at low altitudes, because malaria requires mosquitoes, mosquitoes die below 32ºF / 0ºC, and high altitudes in Africa experience freezes), Epstein-Barr virus (which pretty much everybody on the planet is infected with), and possibly -- possibly -- exposure to natural carcinogens like the sap of E. tirucalli, which grows all over the place and is probably something kids (and everyone else) would be exposed to pretty routinely,9 combine to produce these otherwise unusual cancers in the particular populations that have all three factors. This is just a guess for the moment, but it does have the advantage of appearing to match up to the facts at hand.
So there is actually some reason to think that E. tirucalli might be useful for cancer treatment (and there are studies to that effect already: this one showed that E. tirucalli increased survival for mice with a particular kind of cancer, for example) but more definite reason to think that it would cause cancer, and the two things are connected.10
So don't touch or ingest the sap on purpose, is all I'm saying.11 You won't get cancer from it (unless you also have EBV and malaria -- and if you had malaria, you'd probably know), but don't touch it on purpose anyway.
Having said all that, Euphorbia tirucalli is a popular plant, indoors and outdoors, because it's so ridiculously easy to care for, and the above shouldn't deter you from keeping one if you want one.
Don't look at me like that. I'm serious. It shouldn't.
Exactly how dangerous is the plant, under normal conditions, indoors? Well. This is a matter of some debate, but: the plant by itself, just sitting there photosynthesizing, is not dangerous to you. In fact, nothing short of deliberate application of the sap to a mucous membrane or becoming a Euphorbia tirucalli farmer is likely to matter.12 Driving a couple miles to the grocery store is probably the bigger risk. Also, now that you know that the sap can be problematic, you can take the appropriate steps to protect yourself from it when you're doing stuff to the plant, so it's less dangerous to you now than it was before you knew this. So let's don't lose our heads here.
I ran into a number of sites making comments on how easily the plant will bleed sap if damaged or brushed up against or whatever, but it's been my experience that you can handle them fairly roughly without them necessarily bleeding. I'm not sure if this means they bleed all the time and I just don't notice, or if other people think of "brushing up against" something as a much rougher event than I do. Whatever. It's not like they're going to start throwing sap around the living room if a stiff breeze comes through the window or something. Plants will bleed if cut, or if stems are bent at sharp angles, and that's about it.
When you are intending to break the skin of the plant, like for pruning or whatever, you will want to take reasonable precautions. Minimally, I'd say this means goggles; more ideally you want goggles, long-sleeve shirt, long pants, and closed-toe shoes. Although full body suits are occasionally recommended, I think that's got to be overreacting: the sap does wash off, after all. If you're planning on making a day (or career) out of it, or if you already know from previous experience that you react strongly to the sap, well then yes, full skin covering would be warranted. For just trimming back a branch on a single plant at home, though: c'mon. You're at home: you can wash your hands or take a shower if you have to, especially if this is something you only do once or twice a year. Personally, I've only ever cut my plant back twice, and in both cases it was to get cuttings to send someone; I don't make a habit of cutting it back because I'd really rather it grew big anyway. I find that it's sufficient, for small numbers of cuttings, to cut with the blade coming toward me, and keep a paper towel between me and the stem: that way, if the sap does squirt out, it will mostly go away from me, and if it should squirt toward me anyway, I have the paper towel there to catch it.13
Okay, Mr. S., I'm convinced, I'll get one, but could you tell me how to grow them already?
LIGHT: These are full-sun plants, though my plant has had to live with much less light than that before (for longish periods, actually) and has survived it. In fact, now that I think about it, I don't think my plant got actual sunlight until I'd already had it for like five years. It got kinda etiolated,14 but it still grew (albeit slowly), and lived, and it forgave me immediately when I got better light for it.
WATERING: Like most Euphorbias, E. tirucalli will rot if it's too wet for too long of a period. The best plan is to wait for the soil to get very close to completely dry between waterings. That said, E. tirucalli handles more water than that reasonably well, and it's fairly difficult to kill an established, healthy plant in good soil by over- or underwatering. They're also fairly good about letting you know when you're overwatering: they'll try to get your attention by dropping a couple branches. A good, lean potting mix with a lot of bark, gravel, and sand, without a lot of peat moss, will go a long way toward keeping your plant healthy.
TEMPERATURE: Plants should not be exposed to temperatures below freezing. Although some sites say that you can go colder than that, there are an awful lot of people out there who claim to have lost plants in cold spells that weren't that long or that cold. Still a pretty broad range, compared to a lot of houseplants.
HUMIDITY: Utterly irrelevant.
PESTS: I've never seen any on my own plant or on any of the plants at work. I frankly can't imagine any bug wanting to drink corrosive carcinogenic sap, either. That said, it's always a good idea to watch for scale and mealybugs, even if you don't expect to find any, because they do sometimes go after other Euphorbia spp. Sometimes dried sap on the stems will look like mealybugs for a second: if it flakes off easily when poked lightly with a fingernail, it's just sap.
GROOMING: Very minor: it's actually kind of a neat freak, as plants go. Plants that are too wet will lose individual branches, but these are easy to pull off or pick up, and it doesn't happen often. The tiny leaves also fall off occasionally, though I'm not sure that happens for any particular reason.
FEEDING: Feeding is more or less the usual: half the package-recommended strength, with every watering, should work fine. If your plant is not receiving much sun (because it's winter, or because you have it in a small or obstructed window), you may as well cut back on the feeding too: feeding without providing enough light will only lead to a lot of weak, spindly growth that you'll want to cut off later anyway.
PROPAGATION: From cuttings. Let cuttings dry in air for a few days or weeks and then plant them in a fast-draining potting mix. I've also gotten cuttings to root in plain sand, though I don't recommend it. Rooting is a fairly slow process no matter what you do, but again, more heat and light will speed things along as fast as they can be sped. See also desert-tropicals.com on the subject.
There is one cultivar I'm aware of, called 'Firesticks' or 'Sticks on Fire:' it has the same form as the species, but stems will turn yellow, orange, or red depending on the amount of sun they receive. It's really quite pretty as an outdoor plant; a good photo of 'Sticks on Fire' can be found here. When I've looked at it close-up, indoors, it hasn't really impressed me (it looks like a regular plant that's starting to yellow and die from the top), and I wonder about whether or not it's easy to maintain the color indoors. All the same, I haven't seen any for sale in a long time, and kind of regret not buying one when I had the opportunity.
As with the "person" I've selected to go with it, there's a little ambiguity about whether E. tirucalli is being malevolent15 or just extremely defensive. I gave up watching "X-Files" before the show ended (I quit somewhere in season seven, I think, and that was a season or two too many), so I don't know what Chris Carter ever decided about the cigarette-smoking man's character in the show, whether he was a good guy, bad guy, both, or neither. Wikipedia makes it sound like he was a bad guy. It kinda doesn't matter, since Carter was clearly making it up as he went along and had no intention of wrapping it all up anyway. But I digress. The plant looks like an alien, has mysterious connections to cancer, and talks a lot about energy independence without ever actually producing a single barrel of crude oil: there's something a little unsettling here.
I've been sort of frustrated while trying to write this post, because there are so many conflicting pieces of information out there: for every couple warnings not to touch the sap, there's somebody claiming miraculous healing powers and saying it's totally harmless. With so many different accounts, and no way to know which ones are just copying from one another, who's making stuff up, who has something to gain by making people either more or less afraid of the plant, and who has actual firsthand experience, I have had to try to use my best judgment about how scared I want to make you with this profile.
I enjoy my own personal plant, and aside from it getting a little top-heavy sometimes, I've never had any trouble growing it, have never been hurt by it, never had any pests on it, and I've had it since 2001 (the only plants I've had longer are the gray-variegated Yucca guatemalensis). So it's been a long-term, productive member of the family for a long time, and I'm not going to be eating the stems in my salads, using the sap as shaving cream, or pruning hundreds of them on a daily basis, so I don't lose sleep over having it in the house.
I think there's good reason to use some basic protection when working with this plant. I'm not talking space suits, but goggles, certainly. And it's an especially good idea to remember to wash your hands carefully and thoroughly after working with the plant, lest you absentmindedly touch your eyes or mouth.
I don't think you need to get rid of this plant if you already have it, even if you have small children or pets: I didn't see a lot of evidence that it was very directly poisonous if eaten (unlike, for example, Adenium obesum or Dieffenbachia spp.: for those, I would suggest that people should keep them away from kids and pets, and if that means giving yours away, well, so be it). Sap in the eyes seems to be more serious, though not everybody who's experienced that has necessarily had a bad time.
I do think you should reconsider buying a first one if you have kids or pets in your home. Not because it's that dangerous -- in fact, I won't think badly of you if you go ahead and get one anyway -- but because there are plants with similar looks that pose much less danger, and why take unnecessary chances? Hatiora salicornioides and some Rhipsalis species are less dangerous plants with similar looks. (Indeed, it's possible that the people who report having no problems with E. tirucalli have misidentified the plant: I've seen some very similar-looking Rhipsalis before.)
Use common sense when deciding where to put it. Don't leave it in a place where it can be knocked over easily, or where branches are going to be temptingly low.
If any readers have had run-ins with Euphorbia tirucalli sap, and want to weigh in on the terribleness levels they personally experienced, they are heartily encouraged to do so in the comments.
Fun things to read if you're not already sick of reading about the plant (and don't forget the links from the text above):
Photo credits: Cigarette-smoking man (William B. Davis) was from Wikipedia, though Wikipedia has a different photo up now. Euphorbia tirucalli pictures are my own.
1 Though I could probably be persuaded, for the right amount of cash. Submit bribe proposals by email; you should receive a response within a few days if you edited the address correctly.
2 As opposed to the similar-looking plant drunkard's dream, Hatiora salicornioides, which looks disorganized too but actually has a very regular growth habit: stem sections grow to a more or less standard length, then branch into two or three more stems at the very tip, each of which which then divides into two or three more stems of its own, and so forth. With E. tirucalli, stems can get longer, can terminate in multiple branches, or can send off a variable number of branches from the side as they grow. If there's an underlying system to the growth habit, I can't see it personally.
3 And there are the occasional unverified tales of permanent blindness, too.
4 It's more complex than this, but: Epstein-Barr virus (EBV) is the virus responsible for mononucleosis. It's incredibly widespread: by the time the average U.S. resident hits the age of 40, there's a 95% chance s/he carries EBV, whether or not s/he has ever had mono. Usually, EBV infection occurs in childhood and looks more or less like any other childhood illness: mononucleosis only appears in cases where one has somehow managed to avoid exposure until adolescence. Once the infection has run its course, the virus subsequently goes more or less dormant in one's immune system, and usually that's the last time you're aware of it, though it will re-activate (without any symptoms of illness) from time to time and produce new viruses, which are mostly shed in saliva. The sap from E. tirucalli, specifically the phorbol esters in it, can cause this reactivation to occur, and is also thought to play a role in causing a couple very rare kinds of cancer. Keep reading.
5 As with the famed dog that could walk on its hind legs, the important part is not that it does it badly, but that it's able to do it at all.
6 Though I should note that the same idea of growable gasoline comes up with a lot of other plants in the Euphorbiaceae (as for example Pedilanthus tithymaloides), and yet here we are, still burning oil. The basic idea sounds good, but there are clearly obstacles to its execution somewhere.
7 I wasn't able to confirm that they ever called it this officially and on-camera, but in "X-Files," Scully had a tumor on her nasal cavity's wall, near the brain, which could easily have been nasopharyngeal carcinoma.
8 The going theory is that the carcinogenic agent in the East Asian cases is cured fish and meat, which contain large amounts of nitrites and nitrosamines. It's not really worth getting into what nitrosamines are - we're already on quite a tangent here with the cancer - but you can read the Wikipedia article about them here.
9 As well as a lot of other Euphorbia species, some of which are even nastier than tirucalli, if you can believe it. Go looking for stories about E. cooperi sometime.
10 (A lot of the compounds used in chemotherapy are themselves capable of causing cancer, actually. They're therapeutically useful anyway, because they damage fast-growing, fast-dividing cancerous cells more than they damage healthy cells.)
11 I'm hearing several readers now say, Holy shit, Mr. S: you had me at painful, temporary blindness.
12 It is possible to have a life-threatening allergic reaction (anaphylaxis) to E. tirucalli. An account of anaphylactic shock resulting from Euphorbia tirucalli contact can be found here, and it does indeed sound very unpleasant, but this isn't much of an argument against buying a pencil cactus, since any plant species is theoretically capable of triggering anaphylaxis in somebody.
13 I should note for the record that I have never seen the sap squirt in any direction, personally. But people say it can, and I believe them, so there you go.
14 Etiolation: weak, pale, elongated growth caused by inadequate light. Most often seen on cactus, but it can happen to any kind of plant.
15 It doesn't help me make the case that the plant's not actually evil when floridata.com orders their plant profiles in such a way as to make E. tirucalli plant #666.