Those readers who only look at the plant profiles for the sake of finding interesting and weird plant-related trivia, I'm going to do you a favor and give you the weirdest stuff up front. My new favorite piece of houseplant-related trivia of all time, replacing my Calathea-related favorite from a couple years ago,1 is this: Aloe vera gel, the liquid taken from the centers of Aloe vera leaves, is sometimes used to dilute sheep semen. (Let that sink in for a second.)
You may ask, Why would anyone ever want to dilute sheep semen?
Well I think the real question is why wouldn't you want to dilute sheep semen. What the fuck are you going to do with concentrated sheep semen?2
I don't know why knowing this tickles me so. Perhaps it's just that it was so unexpected. Aloe vera has been used in a lot of different ways through the ages, so I suppose I maybe shouldn't have been that surprised, but . . . well, you know, I wouldn't have thought of overly-concentrated sheep sperm as even being one of the world's problems, much less anticipated that Aloe vera might be the solution.
But so now that we've gotten that out of the way, let me introduce you to Aloe vera.
The first thing to know is that it's sometimes called Aloe barbadensis, and in fact I've been calling it that for the last couple years, because I thought the name had been officially changed. It wasn't until I started researching this post that I found a lot of places, including some that have a lot of credibility with me, like GRIN and davesgarden.com, calling it A. vera. As I didn't come across any explanations for why the name change or any definitive answer on which was correct, and as vera is more familiar to most people and marginally faster to type, I'm going with vera.
There are a lot of things sort of like that about the plant, though. Not only does it have two more or less interchangeable names: the good, pure, familiar vera ("true") and the more difficult, scientific, weirder barbadensis ("from Barbados"), either of which could be correct at any given moment, but we also don't know where it came from, or even whether it's a species at all, originally. Coleus (Solenostemon scutellarioides3) has name-change and obscure-origin problems too: these things happen.
The prevailing theory, as far as I can determine by reading around, is that it originated along the north coast of Africa4 and was spread around all over the place by humans. There are some indications that it may have started out as a hybrid, too: it has certain strong genetic similarities to a handful of other Aloe species that are mostly from northeast Africa.5 Whatever its origin, A. vera now grows pretty much anywhere in the world that's warm and dry enough for it, including Hawaii, India, Australia, Paraguay, South Africa, Jamaica, and southern Europe. Some of this is deliberately cultivated, and some is naturalized.
As with any even remotely medicinal-type plant, people have tried using Aloe vera against pretty much every condition imaginable. In a lot of cases, nothing particularly useful happened, but there are two conditions for which Aloe vera seems to be especially helpful, using the word "helpful" kind of loosely. Both use the leaves, but different parts of the leaves.
The bulk of the leaf contains a gel which is not only a great sheep semen diluent, but it also soothes and speeds healing of burns. This is the use most of us are most familiar with, and Aloe vera's usual excuse for being in people's homes. It's also a mild antibacterial and antifungal, which has led to its use as an aquarium water additive, which is not quite as weird as the sheep semen but is pretty close. The aquarium thing doesn't appear to be widespread at all, though.
Aloe gel has also been used for all kinds of other skin conditions, and even quite a few non-skin conditions: as far as I could tell from sifting through the information I found, there's not a lot of scientific support for using Aloe medicinally aside from treating burns, and Aloe products are not universally helpful when you're talking about burns. For example, although Big Aloe would have you believe that Aloe vera gel can act as a natural sunscreen and prevent burns, this is not supported by science. (Try it for yourself, if you like.) It's also unproven for treating burns caused by radiation (X-Rays, radiotherapy for cancer, etc.), apparently, though I found many people willing to say otherwise, and the skin is too damaged in a third-degree burn for Aloe gel to help much. Still, your normal household burn is likely to be just a first-degree, so they're worth having around.
The antibacterial action I mentioned earlier has been scientifically demonstrated, and bacteria in petri dishes have died and everything, though it's not clear how useful that actually is in real-life situations. Tests on how quickly wounds healed when Aloe vera gel was applied, for example, have given conflicting results. People also sometimes drink the juice to get rid of stomach ulcers (which are caused by bacteria), but again, it's unclear how much that helps.
As for every other product that makes the claim, there's no evidence that rubbing Aloe vera gel into your skin will reduce wrinkles and make you look fifty years younger, but you probably already suspected that.
There's such a long list of other health problems that Aloe vera has been used to treat that I'm going to stick it in a footnote. I do not necessarily encourage or endorse the use of Aloe vera, topically or internally, for any of these conditions. People have tried it, but that doesn't mean it worked.6
Basically everybody recommends that pregnant women or nursing mothers not use A. vera products; pregnant women shouldn't because it can trigger contractions and miscarriage, and nursing mothers shouldn't because it's not known if any chemicals from the plant are expressed in breast milk, or how it might affect an infant if they were.
There's a second, somewhat less pleasant, main use, from the layer of cells just underneath the surface of the leaf, though, which contains a bitter yellow chemical called aloin.7 Aloin, taken internally, is a laxative. It basically irritates the lining of your colon so that it contracts more often and harder, pushing everything along faster, and at the same time it interferes with the body's ability to reabsorb water from the intestines. So, once everything's been pushed to the appropriate place, it's a lot wetter (and therefore softer) than it would otherwise be. If everything works the way it's supposed to, that is. If you overdo it, you wind up with painful cramping and diarrhea, which would be a strong incentive not to overdo it.
However! The U.S. Food and Drug Administration prohibited production of over-the-counter laxatives containing aloin in 2002, due to concern about its safety and the potential for side effects.8 They still permit its use as flavoring (for certain alcoholic drinks; I don't know which ones), or in "herbal supplements," which is just a tiny, tiny taste of the reason why the whole herbal supplement market in the U.S. makes me really uneasy.9 Other species, including A. ferox (also sometimes grown as a houseplant or garden succulent), also contain aloin, and in the past, they were also used in its manufacture. People also occasionally drink Aloe vera juice, either on its own or mixed with other juices, and although these products don't use the aloin-containing layer, trace amounts of aloin may be present in the final product; heavy consumption of Aloe juice can lower blood potassium to dangerous levels, among other things, though I'd think you'd have to be trying pretty hard to give yourself that kind of problem.
A few remarkably unlucky people also find their skin irritated by Aloe vera, specifically the yellow aloin-containing layer, and get rashes and stuff. (Which is too bad, because you know what's really good at clearing up skin irritation?)
So the plant does have some legitimate health-sustaining credentials, but you don't want to go throwing it into everything all willy-nilly just because it's Natural and therefore Good For You, because it's got a bit of a dark side too.
The appearance of the plant is also a bit two-faced. Maybe even three-faced. Very young offsets are usually green or blue-green with white spots, with leaves arranged in two stacks opposite from one another. As they age, leaves remain spotted but start pointing their leaves in all directions, forming rosettes. This middle phase is how plants are usually sold. At some point after that, if they're happy, there's a second transition when they lose the spots and become huge. This confused me once at work; someone brought in a plant they said was an Aloe vera, in a big pot, but it didn't look like one to me -- it was much too big, didn't have spots, and was yellowish-green instead of bluish-green. The yellow-green was explainable if it had been getting a lot of sun; Aloes frequently turn reddish in bright light. But I didn't actually believe it was an Aloe vera until a few months later, when it flowered (yellow, tubular flowers on tall stalks) and I was able to check the flowers against the internet, and then it produced offsets which were obviously Aloe vera offsets, so I became a believer then.
A few sites call the spotted and non-spotted forms distinct varieties of the plant, but they're obviously not stable varieties, since one changes into the other over time, see the above picture.
Care for Aloe vera is pretty straightforward succulent-plant care, nothing terribly tricky:
LIGHT: More is better, and ideally full sun, but plants can get by on less if they have to. One of my plants is in a filtered sun / bright indirect spot in the plant room, and has been doing fine with that. It's maybe not growing as fast as it would like, and it's not as blue as it would be in brighter light,10 but it does fine. The others are under very bright artificial light, and do well there. They're equally flexible outdoors, though in full outdoor sun the leaves will redden. This is normal, and will go away if the amount of light drops. Plants that have been grown indoors in lower light will sunburn if suddenly placed in bright outdoor sun.
WATERING: Typical succulent watering. Use a fast-draining, fast-drying gritty potting soil. Drench the plant, then wait for it to get completely or almost completely dry, then drench it again. In the winter, water less often, or not at all (see TEMPERATURE and PESTS).
TEMPERATURE: Outdoors, Aloes can handle brief light freezes -- sometimes. Accounts vary. It looks like once you go below about 50F/10C, the odds of a plant surviving start to drop, particularly if the soil is also wet, hence the need to water less in the winter.
I'm not aware of any upper limit on temperature (they are from northern Africa, after all), though I assume there must be one, and one person in the comments at davesgarden.com said that they're more prone to root rot if watered when it's hot. This doesn't make a lot of sense to me (Northern Africa! When would it not be hot?), but I don't have any actual personal experience on the matter, so I suppose it could be true. If you can stand the temperature, your Aloe probably can as well.
The gel is said to lose potency when heated or exposed to air, and doesn't store very well as a result. This probably doesn't matter to you if you're just breaking an occasional leaf off of your plant at home to treat burns, though it might make a difference in how you should store products containing Aloe vera.
HUMIDITY: Not much of an issue for this plant.
PESTS: Not especially prone to pests, though scale and mealybugs are always possible. Root rot is also a common problem, if plants are too wet, particularly if it's also cold.
PROPAGATION: Plants will eventually self-propagate through offsets. Although the plant used as the example is actually an Alworthia,11 not an Aloe, the basic procedure from this post works just as well for A. vera; I've done it myself.
The impression I get from the way people talk about them, and from my own personal experience, is that a plant's inclination to offset is mainly a function of how much light it's getting. Outdoor plants in warm climates are said to be practically a pest, they offset so much. My indoor plants under fluorescent lights have started to offset a little bit, despite still being babies themselves; the one in the plant room, getting less light, hasn't offset at all.
GROOMING: Not a lot of grooming to be done. I find that occasionally leaves will develop flattened sections, especially near where the leaf rests on the edge of a pot. Once that starts, I'm not aware of anything you can do to reverse it, but it will eventually spread across the width of the leaf. Sometimes it stays like that, and sometimes it dries out and turns black and brittle, at which point you can pull off the end.
I don't know specifically what causes this, but my suspicion is that it must be mechanical injury: the ones that get moved around most seem to be most prone to doing it, and often it begins where leaves touch their pots, which suggests that there must be something special about that spot. Bruising is all I can think of. If anybody has a different theory, I'm all ears -- none of the research even mentions this, never mind explaining it. (UPDATE: Oh. Actually one of them did. It says that black spots on the leaves are caused by overwatering. We might be talking about different kinds of black spots, though.)
FEEDING: Normal houseplant fertilizer, according to label directions, though you can skip winter, especially if your plant is going to be in a cold spot. They don't exactly go dormant -- if you have a spot that's warm year-round, they'll grow year-round -- but if it's cold enough, you won't be watering that much anyway.
There aren't any cultivars of Aloe vera as far as I could find, which is kind of surprising. I mean, you'd think with a plant that's been cultivated for thousands of years would have accumulated some interesting or pretty mutations, but if they're out there, they hide well.
Aloe vera is also one of the plants which have been tested for their ability to remove volatile organic chemicals from air. I'm not terribly impressed by this (I suspect that if you tested the species used as houseplants, you'd find that they all clean air to some degree or another), but some people are, so I mention it.
I remind the reader also that Aloe vera will be useful during the zombie apocalypse, mostly for those whose zombie-proofing includes flamethrowers. And even without zombies, any apocalypse is going to be hell on the skin. Can't hurt to have a couple Aloe veras around. More than that, you'll be prepared if there's a sheep semen apocalypse.12
I can't quite visualize what a sheep semen apocalypse would look like, though the parts I can imagine are very disturbing indeed. It's definitely not the kind of thing you want taking you by surprise.
Select references (The list of everything I looked at, whether I used it or not, would be too long and pointless, and would include a lot of advertising for beauty care products that don't deserve free advertising.):
Wikipedia (Aloe vera)
Memorial Sloan-Kettering Medical Center (Aloe vera) (medical/technical)
Poisonous Houseplants (aloin)
ILoveIndia.com (questionable info about medicinal uses)
Zanthan Gardens (blog post about outdoor Aloe vera flowering in Austin, TX)
FlowersInIsrael.com (mostly historical stuff I didn't use in the profile, but interesting)
Davesgarden.com (comments are more informative than the profile)
Wignet.com (.pdf about a case of a woman who gave herself hepatitis with Aloe vera tablets "in the hope to delay aging")
University of Maryland Medical Center (medical/historical)
Photo credits: Mine except as otherwise noted.
1 (that bats sometimes sleep in the rolled-up, newly-developing leaves of Calathea spp., in their native habitat)
2 To answer the question seriously, though: it has to do with artificial insemination. A single ejaculate from a ram contains enough sperm to inseminate lots of female sheep, but if you use it all up on one female then obviously a lot of it has gone to waste. And who wants to spend more time jacking off sheep than they absolutely have to, right?a So, you find something to dilute it with, and then you can inseminate many, many sheep, instead of just the one. Why and how Aloe vera gel came to be used for this purpose, as opposed to something simpler like plain water, I have no idea, and it's not necessarily an incredibly widespread practice -- the source didn't say -- but still. How can you not love knowing that?
a (I'm fairly certain this is not how sheep semen is actually collected.)
3 (Except that now it might be Plectranthus scutellarioides. Having gone to the trouble of learning Solenostemon, I intend to use it for at least a little while longer before switching to Plectranthus.)
4 The eastern part of this range, along and around the Arabian Peninsula, overlaps with the home range of Coffea arabica and some Adenium species. Its original range is also thought to extend as far to the west as the Canary and Cape Verde Islands. Barbados, of course, is nowhere near any of this, which makes me wonder how and why the A. barbadensis name happened.
5 Most of these aren't species you've probably heard of -- the strongest links were to A. perryi, A. forbesii, A. inermis, A. scobinifolia, A. sinkatana and A. striata. Striata is the oddball: it's from South Africa, while the others are from Yemen, Somalia and Sudan. Striata is also, as far as I know, the only species in the list to be deliberately cultivated on any kind of noticeable scale.
I couldn't find an answer for why the similarities lead people to think it's a hybrid. It seems like the simpler explanation is that it has a recent common ancestor with A. perryi and the others, which would be easy enough to do, since they all live in the same place already. But apparently the DNA suggests a hybrid origin, or that's somebody's pet theory, or something.
6 Heartburn, long-term management of blood sugar levels in diabetics, allergies, acne, psoriasis, shingles, high blood lipids, irritable bowel syndrome, cancer, herpes, asthma, fungal infections, ulcers, gingivitis, blisters, insect bites, rashes, vaginal infections, [male] genital sores, pain, conjunctivitis, hemorrhoids, dry skin, sunburn, frostbite, eczema, arthritis, baldness, the plague, fever, bladder infections, kidney infections, insomnia, leg cramps, and on and on like that.
Inappropriate use of Aloe vera can lead to: low blood potassium, blood in the urine, thyroid problems, hepatitis (reversible if the Aloe is discontinued), hypoglycemia, slower blood clotting, severe abdominal cramps, diarrhea, and probably other stuff.
It is just a plant, remember; it's not magic.
7 Technically it's a pair of chemicals called aloin A and aloin B. The difference is already way past the scope of this post, but if you really care, you can also probably understand the Wikipedia entry on Aloin so you should just go there.
8 According to one source, the specific reason was that they think aloin might be carcinogenic, and wanted to stop sale until someone can prove that it's not. I didn't find anything specific about why they think this, but molecules with large flat regions like the anthraquinone part of aloin can often slip themselves into the spaces between bases in DNA, distorting it and causing it to be misread by the cell in ways that lead to cancer later. This is also way past the scope of the post, but if you're interested, Wikipedia's page on intercalation (the fancy name for molecules fitting themselves in between bases in DNA) should tell you what you need to know.
I emphasize that we don't actually know whether this happens with aloin, and even if it did, that doesn't mean that products containing Aloe vera juice or gel will give you cancer. Aloe vera leaves being harvested for gel or juice are sliced up in a way that removes the outer, aloin-containing layer. So your shampoo, sunscreen, shaving lotion, etc., are all safe and will not give you cancer. Or, if they give you cancer, it's probably not the Aloe vera content that's responsible, anyway.
9 Not the husband, though: he takes some. Don't know which specifically. He's had, in the past, a bad experience with an aloe-containing "herbal supplement," though, so we don't let those in the house.
I at one time took St. John's Wort for depression, though I suspect it was just an expensive placebo. While I did get better during that period, I also started taking it at more or less the lowest moment of my life, following a couple of fairly big life upheavals. If I'd taken circus peanuts for the depression instead, I'd probably have seen just as much improvement. (Check out regression toward the mean.)
I'm fine with the idea of herbal supplements, but I think they should have to demonstrate in scientific, double-blind tests that they do what they say they're doing, and that they should be regulated to make sure that they contain the active ingredients they say they contain. At the moment, the producers of herbal supplements are not legally required to do either one of these things, which is why there's the disclaimer on all of them:
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.I.e., "use at your own risk," basically. Which is fine and everything, but it doesn't prevent them from making health claims, it just means they have to make really vague ones, like "boosts the immune system" or "provides energy."
You use regular pharmaceuticals at your own risk too, the difference being that there's supposed to be proof that they work, and they're supposed to be checked regularly to make sure that they contain the stuff that was shown to work, and you have to have at least a cursory conversation with two supposedly smart, highly-educated professionals (doctor and pharmacist) who can warn you if they're not likely to be good for your particular situation or if there are concerns about safety. The FDA could be doing a better job, it's true, but even a crappy FDA, plus doctors and pharmacists, is better than the honor system, which is essentially all you've got with the herbal supplement crowd. The FDA at least doesn't usually allow pills full of lead, arsenic, and pesticides to go out for sale, after all. Some herbal supplement companies are said to be more conscientious about this sort of thing than others, but I don't know which ones, or how much better, or whether this is true at all.
10 The blue coloring of Aloes, and lots of other succulent plants (Sedum morganianum, some Agaves, etc.), is a layer of wax produced by the plant, confusingly called "bloom," which reduces moisture loss and reflects excess sunlight. It also helps keep dirt and water off the leaf. Bloom will rub off, if plants are handled, which doesn't especially hurt the plant, though it does make it look less pristine. Plants grown in lower light may produce less bloom in order to collect more light, which I think is why my plant room Aloe vera is greener than the ones in bright fluorescent light in the basement.
11 Aloe species can hybridize both with one another and with plants in the related genera Haworthia and Gasteria. The Aloe x Haworthia hybrids are usually called Alworthias, and the Aloe x Gasteria hybrids are Gasteraloes.
The post calls 'Black Gem' an Aloe because I thought it was at the time. I've since found out it's an Alworthia, but it's a fairly time-consuming affair to go through the whole blog to change a name. It'll get fixed eventually. (UPDATE: It was.)
12 ("What am I gonna do? What am I gonna do? I'm gonna get in there and dilute the sumbitch, that's what I'm gonna do. GERONIMOOOOOOOOOOOOO!!!!!")