I had a very difficult time coming up with a "person" to go with the Schlumbergera profile. The most scientifically-relevant feature of the plant, or at least the one I found most interesting, is that they're not self-compatible, meaning that Schlumbergera plants cannot pollinate their own flowers or the flowers of closely-related plants.1 This turns out to have interesting repercussions, when it comes to developing new varieties, but there isn't an obvious human parallel. Individual humans can't . . . *ahem* . . . self-pollinate either. So I went 'round and 'round on that question for a while, trying to figure out what "person" could go with that.
And then things got even worse, when I got myself further hung up on a technical issue having to do with not quite understanding how the self-incompatibility thing works.2, but it's long So then I had to try to find a new "person" entirely, and there were a lot of internal debates about whether or not I should write a 2-part profile (which I didn't want to do: two-parters are a lot of work) or throw out a lot of the 33 pages of notes I'd taken3 (which I didn't want to do either) and so now here we are. "Tease" isn't completely satisfying either, but it works for a couple specific points, and anyway if we'd waited until I came up with a person I liked better then this profile wouldn't go up for months. I'm pleased to say I have more solid "person" selections in mind for the next couple plant profiles.
So anyway. The genus Schlumbergera (sometimes called Zygocactus, though this is no longer correct) is native to southeast Brazil, particularly the four Brazilian states of Rio de Janeiro (yup, it's also a state), Espírito Santo, São Paulo, and Minas Gerais.4 The plants live in the forks of tree branches, on rocks, or in crevices on cliff sides, and collect their own "soil" by accumulating plant and animal debris as it gets caught on the Schlumbergera's base.5 The flowers are pollinated by hummingbirds.6
As best as I can tell,7 there are six species of Schlumbergera: kautskyi, microsphaerica, opuntioides, orssichiana, russelliana, and truncata. All six are rare or endangered in the wild.
For our purposes, when talking about houseplants, really only S. truncata, and the truncata x russelliana hybrid called Schlumbergera x buckleyi, are relevant. Other crosses among the six species have occurred -- Schlumbergera species appear to be mostly, though not totally, capable of hybridizing with one another -- but they have not, so far, proven to be useful in creating commercially viable plants, so you're unlikely to meet a plant that isn't truncata or buckleyi.
S. truncata, on the other hand, has been cultivated in the western world since 1816 or 1817, when the first specimen was brought to Kew Gardens in London. S. x buckleyi was first produced in the late 1840s by a man named William Buckley,8 at the Rollisson Nurseries in London, and has been crossed, re-crossed, and selected since then to produce some of the Schlumbergera varieties one sees in stores. Three clones of Buckley's original crosses are said to survive: 'Buckleyi' has a white tube which shades into magenta at the petal tips, 'Rollissonii,' which is magenta, and 'Snowii,' which is likewise magenta, but with smaller flowers and stem segments.
In the wild, S. truncata flowers in May, and is therefore called "Flor-de-Maio" ("Mayflower") in Brazil. In the Northern Hemisphere, though, the plants usually flower in November, left to their own devices. They're sold in the U.S. as "Christmas cactus," though the more pedantic Americans call them "Thanksgiving cactus." (The pathologically non-committal go with "holiday cactus.") In any case, wherever they are, they're going to try to flower in late fall, often with a smaller, secondary bloom in the spring.9 Plants sold for Christmas sale are usually manipulated to bloom on or near Christmas; in subsequent years they will bloom in November instead unless special steps are taken.
Some true Christmas-blooming cacti exist, which are S. x buckleyi, but these are not currently fashionable and are also hard to find. (Actual Christmas-bloomers come into flower a bit too late for holiday-season sales. Also, people prefer more upright plants, and the stems of Christmas-blooming Schlumbergeras tend to arch over and leave a bare spot at the top of the plant. Even if people didn't prefer them, growers prefer upright plants, which are easier to grow and ship.10) Christmas-bloomers typically have stem segments with rounded edges, instead of pointed like on pure S. truncata varieties. Some families are lucky enough to have a true Christmas cactus which has been passed down through the generations. Mine's not one of them.
Another sign of the difference between Christmas and Thanksgiving cactus is in the flowers themselves -- most commercial Schlumbergeras have unusually-shaped flowers that one source described as "leaping shrimp." These have a left and right side, with only one axis of symmetry, and are called "zygomorphic" flowers. Thanksgiving cacti are also available in a much wider color range: red, pink, white, magenta, salmon, yellow, and bicolored flowers like 'Caribbean Dancer.' True Christmas cacti, on the other hand, are almost always red or magenta and have "actinomorphic" flowers, like most other cacti. Actinomorphic flowers have multiple axes of symmetry and petals which all radiate equally away from a common center, like a daisy.11
Actinomorphic flowers, Christmas flowering, weeping habit, and rounded stem segments12 all typically go together, but there are exceptions for every combination. Your best bet, if you really want a true Christmas cactus, is to make lots of friends who
Or at least sometimes they are. The deeply misanthropic or socially inept can try their luck with eBay or Craigslist or something.
There also exist Easter cacti, as mentioned in footnote 11. They look very similar, but only bloom once a year, and are Hatiora or Rhipsalidopsis species, not Schlumbergera. Easter cacti aren't particularly popular because they're harder to grow: if they're in a draft, too wet, or too dry, they shatter, dropping all the stem segments, which is obviously kind of a jerky, passive-aggressive thing to do. Also they're less consistent bloomers. Which is also passive-aggressive. Basically Easter cacti are pricks, is what I'm saying. Care is basically the same as Schlumbergera, but the margin for error is much narrower. Easter cacti are also fairly tough to locate: in this case you're probably better off on Craigslist with the misanthropes.
There's a lot of advice on-line, and everywhere else, about how to grow Schlumbergera, much of which contradicts other parts and is very confusing. However, for your convenience, I have condensed what I found below:
LIGHT: Indoors, you want bright indirect light or artificial light during the summer, and some direct sun in the winter. Some people keep their plants outdoors during the summer; if you do so, place them in a bright spot with no direct sun. Plants which are getting a lot of light will often turn reddish or pinkish, and if buds are forming, flowers will usually be pinker than normal. This is harmless, according to everything I read, though of course it's also a strong hint that you're overdoing the light.
Day length is part of the trigger for flower bud formation: Schlumbergera will not bloom if the day is longer than about eleven hours. Artificial light counts just as much as natural: keeping a Schlumbergera in a room where lights are on after sunset can prevent it from setting buds. Allegedly, even a streetlight shining through a window can be enough to delay or prevent blooming, though my plants have never had perfect, total darkness at night and still bloom okay, so I'm not sure I believe that.
WATER: Never let the plant stand in water, but keep the soil evenly moist from about March until the end of the November or December flowering. Between Nov/Dec and March (in the Northern Hemisphere), let the top of the soil dry out before watering again. Schlumbergeras will tolerate dryer conditions than this if they have to (mine do), though you may see slower growth if the plant is kept too dry. Be particularly careful not to overwater when the plant is cold: this makes them much more susceptible to rot.
One site said that holiday cacti dislike hard water (water with a lot of dissolved calcium and magnesium), and recommends watering with rainwater instead. Which I guess you can do if you want to. If your home has a water softener, do not use softened water on your Schlumbergera. In fact, don't use softened water on any houseplants.13
One occasionally sees the advice to withhold water from a plant in order to induce it to bloom. The Schlumbergera professionals say that this practice can harm the plant over the long run, and also that it doesn't even trigger blooming: everybody's pretty firm that day length and temperature are all that matter when it comes to getting flowers.
None of my sources recommend the exact same soil mix as any of the others, though peat moss tends to be a major component: it's acidic, which they like,14 plus it holds water and has an open enough texture that air can still reach the roots. Almost everybody's mix is mainly peat moss, with some added perlite or coarse sand. This is one situation where Miracle Gro might prove useful, as it's mostly peat. Two parts Miracle Gro to one part perlite should make a serviceable potting mix.15 That said, they're awfully flexible about soil, because in the wild they kind of have to be, so a regular houseplant mix is probably just fine if that's all you have and you're not planning to mass-produce them.
TEMPERATURE: Temperature is, along with light, the other part of the trigger for plants to start setting buds. If you leave your plants outside during the summer, bring them in once the night temperatures start getting down around 50-60F (10-16C). Some plants have been known to survive temperatures as low as 40F/4C, but that isn't guaranteed. Plants with lighter-colored flowers, if exposed to temperatures below 50F/10C, are known to produce flowers which are more pink than usual:16 this is temporary, and will only happen again if the cold exposure is repeated.
(It's worth pointing out that although cool temperatures seem to be important for getting lots of blooms, one doesn't have to keep plants outside in order to get flower buds. My plants have flowered just fine before in an apartment that was kept at a pretty steady temperature, three or four feet away from a bank of artificial lights. Don't get too hung up on the details unless your plant has consistently failed to bloom for a couple years, you want a super-amazing show, or you want your plant to grow faster. Plants kept outside will definitely grow faster than plants kept inside year-round.)
Once flower buds have begun to form, do not let plants get warmer than 90F/32C. Sustained high temperatures can cause the buds to drop. 90F/32C is okay (not ideal) during the summer, though, when there are no buds.
HUMIDITY: Few of the references even mention humidity, though the ones that do sound pretty worried about it. It's been my experience that humidity is not normally an issue with Schlumbergera, though if you live in, you know, North Central Alberta (and somebody must) then you might want to think about a terrarium or something during the winter. The only source that gave a specific recommendation said to aim for a minimum humidity level of 30%, which is not ordinarily hard to achieve.
PESTS: The biggest issue with Schlumbergera is root rot and other fungal diseases, which are usually only a problem if your plant has been badly overwatered or injured. Mealybugs and scale are not unheard of, and plants kept outdoors may experience problems with slugs, but generally holiday cacti are pretty healthy.
Occasionally one will see stem segments with patterns of rings or lines on them; this usually signifies a virus, most likely one transmitted by an insect.17 Plants infected by a virus cannot be cured, and the virus will weaken the plant, leaving it more susceptible to other ailments. So if your plant has a virus, the plant should be destroyed. You may want to get an expert opinion first from a local nursery, University Extension Office, botanist, or experienced Schlumbergera grower.
PROPAGATION: Most people propagate their plants by cuttings. To do this, one just twists off part of the plant: they naturally come apart at the joints between stem segments. Segments that have fallen off on their own can sometimes also be propagated: it depends on how and why they fell.
Usually people recommend at least two segments for a cutting, though anywhere from 1-4 segments are common. Let the cuttings dry out for 2-7 days, then plant in, or lay them on top of, your potting mix. I have historically had mixed luck getting cuttings to root, but I'm also impatient and tend to skip the let-them-dry step, so that's probably why.
For best results, take multiple cuttings from the same plant and plant them together (this will give you a fuller-looking plant sooner). You'll know rooting has started to happen when you see new growth appearing at the tips of the old stems.
Less commonly, people propagate from seeds, which is much more complicated and time-consuming. You'll need at least two plants which are flowering at the same time (or one of the few cultivars that are self-fertile), and ideally two flowers which have fully opened within the last two days.18 The stigma is the longer, pink- or red-purple-tipped thing sticking out of your flower; the pollen is yellow and doesn't stick out as far. Brush the pollen from one flower onto the stigma of the other, and vice-versa, and you're done. If the two varieties have different self-compatibility genes, and neither has an odd number of chromosomes,19 fruits will begin to develop on your plant.
The fruits are about an inch long at full maturity, and in warm growing conditions take about six months to mature.20 Mature fruits may be white, pink, red, or purple, and will contain anywhere from 25 to 300 individual seeds. Schlumbergeras are a little unusual in that the fruits will stay on the plant indefinitely if undisturbed. If fruits stay on the plant for too long, some of the seeds can start germinating while still inside the fruit.
When fully ripe, the seeds are brown or black. One extracts them from the fruits by slicing open the fruit, putting the goop inside the fruit into water, stirring vigorously to separate them from one another and from the goop, and then pouring them out onto paper to dry. Mature seeds are easily germinated if kept moist and warm (72-77F / 22-25C), or they can be stored in a dry refrigerator at around 40F/4C for future use. Seeds can keep for ten years or longer. Seedlings are usually large enough to take cuttings from within about one year of germination, given good growing conditions; the process of determining whether one has a plant worth propagating, though, takes about three or four years, sometimes longer.
One is also almost certain to be surprised by the results: the genetics of Schlumbergera flower color are complicated and not fully understood. You can cross a salmon with a salmon and wind up with 200 white seedlings, or cross a pink with a yellow and get purples. Spontaneous mutations also sometimes happen, though since spontaneous mutations tend to be recessive, it can take years to get them to show up: you have to get two copies of a recessive gene in a plant before you can see what it does, and Schlumbergera self-incompatibility means that you can't just cross a plant with itself, or a close relative, to get the two recessive genes together. In fact, Schlumbergera breeding in general sounds like a frustrating business: anytime you get a trait you like, no matter how you got it (induced mutation by irradiation, hybridization with another species, good old-fashioned random crossings followed by selection of the most interesting ones), you have to cross it with something that doesn't have that trait immediately, diluting the genes you want, because they aren't self-compatible. Developing a single new variety can take many years, and requires evaluation of a huge number of seedlings: this is even more the case when trying to create characteristics not found in nature, like yellow flowers.21 Plant breeding in general is slow and frustrating, but it's got to be even worse when your subject teases you like this, showing you cool stuff but then not letting you refine your results without going through multiple non-productive crosses first.
Of course, that really only matters if you're breeding plants to make a living. If you're just making random crosses at home for your own entertainment, it's a lot less stressful. Most of the above is adapted from information about the professional, large-scale preparation of seeds; for a more personal look at the procedure by someone who's done it, Happy Hobby Habit has a very nice, well-documented post with lots of pictures here.
FEEDING: Recommendations vary a lot, again. Different sources recommended balanced (20-20-20), high-phosphorous (15-30-15), and high potassium (9-9-26) fertilizers; I suspect, based on who was saying what and how well they seemed to know what they were talking about, that switching to a high-potassium formulation for most of the year is probably best. Mix it at 1/2- to 1/4-strength, and feed at every watering. Stop fertilizing in September, and don't begin again until you see new growth starting to form in the spring.
You'll also need to flush the soil occasionally, to keep salts from building up in the soil. This is pretty easy: stick the plant in a tub or sink, and pour water through the soil several times. Let it drain well, put it back in place, and you're done.
GROOMING: Plants can go for a very long time between repottings. I rooted a salvaged cutting from work in a three-inch (7.6 cm) pot containing nothing but an inch of vermiculite and one or two balls of Osmocote at the bottom, and it grew and flowered and seemed totally happy with that situation for about two years.
Some sources say that plants will only bloom well when rootbound. I don't know whether that's true, but repotting is rarely an emergency, and potbound plants will certainly bloom just fine under most circumstances. If you do move your plant into a bigger pot, use a pot which is not much bigger than the old one, say, from a 5-inch pot to a 6-inch one. Shorter pots are also generally better than taller ones: an azalea pot's proportions (where the height is 3/4 of the width) are about ideal.
If you decide to keep your plant in the same pot for a long period, you'll still want to change the soil regularly, since it breaks down over time. This basically amounts to taking the plant out of the pot, loosening the root ball with your fingers and/or scoring the sides with a knife every few inches, shaking off what soil you can, and then replacing the plant in the same pot with fresh soil. I'd recommend doing this every two or three years, though again, if you don't get to it as soon as you meant to, it's probably not an emergency.22
Some people prune their plants after they bloom in winter, to keep the plant looking rounded and bushy -- some hybrids are prone to produce long, straight branches that look funny. This isn't something I've ever worried about personally, because none of mine have been around long enough to do this. If you do want to prune, twist the segments off, rather than cutting them. The segments you remove can be used to propagate new plants, or planted in the same pot with the original, if you are so inclined.
Bud drop can be a big problem with Schlumbergeras, particularly a plant is moved or rotated while buds are developing. It's not exactly the movement itself that does it, and the plant isn't trying to frustrate you: the problem is that the buds orient themselves toward the light, and if the plant is moved, the buds can turn hard enough that they'll twist themselves right off.
Bud drop can also be caused by changes in temperature (particularly long periods of exceptional warmth: don't bring one home and stick it next to the radiator), excessive or inadequate watering, or ethylene gas (don't put your plant next to a bowl of apples when you get it home, for example).
Twice while I worked in the garden center, we ordered plants in bud from our supplier in Florida, and when we got them priced and out on the tables, most of the buds dropped immediately.23 This can also happen, obviously, with newly-purchased plants one brings home from the store. The solution? Get your plants before they're in bud, or get them when they're so close to opening that they'll still open, even if they twist their way off later. Even if there is some bud drop, plants that drop all their buds early enough in the season will often scramble to produce some new ones: it won't be as big of a show, but you'll still get something.
Another cause of bud drop involves the chemicals growers use to force flower production. Benzylaminopurine, or BA, is a natural plant hormone which increases the number of buds produced by each segment of the plant, and a lot of growers use it. This is the likely explanation for a plant I saw a few years ago, with nine flower buds on the same segment:
The problem with this is that a single stem segment can't actually produce this many flowers. There just isn't room. So, some of them get squeezed out and fall off. This isn't the plant's idea, and shouldn't happen to you the following year.
Despite the profile name, and the fairly specific and unusual care instructions, these are pretty tough plants, which are among the easiest plants (if not the easiest) to bring into flower indoors. I think they're pretty cool-looking when not in bloom, too, and would grow them even if they didn't flower, though I think that's a minority opinion.
Whatever your feelings about the shape of the plant, they're well worth trying. One doesn't get many opportunities to buy a plant that could still be around fifty years later.
Sources / additional reading:
N.O. Anderson (ed.), Flower Breeding and Genetics, pp. 361–388. © 2007 Springer. (Also keep in mind that Interlibrary Loan exists, at least in the U.S.)
Plant of the Week (brief care description)
Desert-tropicals.com (brief care description, habitat, propagation)
Wikipedia page for Schlumbergera (habitat, species, naming)
Cactus and Succulent Society of America (mostly how to bloom and propagate)
Cactus and Succulent Society of America (species, natural habitat, general care)
Missouri Botanical Garden (basic care)
Claw Cactus (description, species, general care) *recommended*
Happy Hobby Habit (starting Schlumbergera from seed) *recommended*
Suite 101 (general care)
Telegraph.co.uk (general care, some history)
Marthastewart.com (general care)
Toronto Botanical Garden (general care, some trivia)
Our Little Acre (personal feelings toward, very basic care)
Garden Notes (mostly about S. x buckleyi)
Mr. Brown Thumb (distinctions between Thanksgiving and Christmas cactus)
Mr. Brown Thumb (pollination of Schlumbergera)
Mr. Brown Thumb (tips for getting Schlumbergera to bloom)
Recognition and Culture of the Holiday Cacti (care, also diagrams of flower parts, photos of Easter cacti) *recommended*
Garden Hacker (propagation from cuttings) *recommended*
The Genetics of Self-Incompatibility in the Genus Schlumbergera (extremely technical stuff about self-incompatibility in Schlumbergera specifically, as measured by trying to self-cross plants; .pdf format)
Self-Incompatibility (brief but jargony descriptions of different types of self-incompatibility: Schlumbergeras use GSI, about halfway down the page)
Wikipedia (even more jargony, about self-incompatibility)
GRIN page for S. truncata
GRIN page for S. kautskyi
GRIN page for S. microsphaerica
GRIN page for S. opuntioides
GRIN page for S. orssichiana
GRIN page for S. russelliana
Photo credits: Mine except as otherwise noted in text.
1 There are a few out there which can, both species and cultivars, but they're uncommon.
2 I understand how it works, in that I understand what happens when a plant's own pollen lands on its stigma. It's basically that each plant produces a gene, or set of genes (not clear in this case), which can produce either a "Lock" or a "Key." The Lock produced by one gene fits the Key produced by the same gene.
Because this is the part of the plant's genes which determines whether or not it can self-fertilize, plants ordinarily have two different versions of this gene. So say we have a plant, and it's carrying version 1 of this gene or genes on one chromosome, and version 2 of the gene on the other chromosome of that pair. (All six Schlumbergera species have eleven pairs of chromosomes.)
When our plant goes to form pollen, each of the pollen cells is going to get either the Lock&Key gene in either version 1 or version 2. This pollen lands on the stigma of a different plant, and it immediately begins building a "pollen tube," which is how the pollen cells reach the ovary of the plant.
The pollen cell, while it's doing this, is also expressing the Lock version of its genes. Let's say it got version 2 of the self-compatibility gene(s), so it's making Lock2. The stigma (the female part of the plant, in which all this activity is happening), meanwhile, is making keys that fit its particular genes. If the stigma is making Key3 and Key4, or any combination that doesn't include Key2, then the pollen tube keeps going until fertilization happens, and eventually you have a seed. But if it's making Key2, the Key2 fits the Lock2, the pollen tube stops construction and is soon torn down, and you wind up with no seed from that particular grain of pollen.
So far, so comprehensible, but the part I can't figure out is what keeps these gene(s) honest. Because, suppose a plant appeared which was a mutant of some kind: it makes a Lock-Key pair that don't fit one another, on one of its chromosomes. Let's call the mutant Lock@-Key#. If one chromosome has the @# genes, and the other chromosome has version 1, then half of its pollen will make Lock@, and half its pollen will make Lock1. Its stigmas will all be making Key# and Key1. So 3/4 of the time, it will be able to form seeds, instead of only 1/2 of the time, plus it'll be more successful with its recent relatives too, who are most likely nearby. So in theory, plants with this mutation would produce 50% more seeds than the plants with honest genes near them. And then in the next generation you'd have a bunch more of these plants with the @# gene, who would also produce more seeds, and eventually the whole population would be self-fertile plants that all had identical @# genes on both chromosomes.
Since this hasn't, for the most part, happened in nature, that means that there's got to be some fairly big penalty for making cheating genes. Maybe something about the way the gene(s) are constructed means that incompatible Locks and Keys are just impossible -- though that seems unlikely, since some species and cultivars are self-fertile. Maybe there's a stage during the embryo's development, when it's becoming a seed, where the Lock-Key fit is checked, and if they don't fit together properly, the seed aborts. Maybe Schlumbergeras in the wild are always just on the edge of being too inbred to make it, so any cheating genes like this get wiped out soon because the plants that make them aren't resistant to a fungus or something. I don't know. Obviously there's something. But it really bothers me that I don't know what that something is.
Which is why I wasn't going to cover this in the profile, because it felt like I didn't understand what was going on well enough to explain, but I guess I've just more or less explained it anyway so oops.
3 Less impressive than it sounds; quite a bit was redundant. But it was still a lot of notes.
4 Much of this is also the original home of the Tupi people, whom we encountered in a different context in the Ananas comosus profile.
5 This is surprisingly common, for the plants grown as houseplants. Just from the plants I've written profiles about so far, five (Aechmea fasciata, Selenicereus chrysocardium, Phalaenopsis cvv., Hylocereus undatus, and Hatiora salicornioides) are epiphytic in the wild, and two others (Anthurium andraeanum and Ficus benjamina) are partly so. My guess at an explanation: light levels. Indoor plants have to make do with a lot less light, and plants that naturally grow shaded by trees have an advantage in that department.
6 (Yet another overlap between Schlumbergera and Ananas comosus.)
7 Sources disagreed about how many there were and what they should be called; I'm going with the USDA's Germplasm Resources Information Network (GRIN) site, for a number of reasons, chief among them that GRIN is boring in the way that authoritative things are frequently boring, but then also it matches most of the other boring lists.
8 One source has this as "Wilbraham." One wishes this were true, because it's a rockin' name, but it doesn't seem nearly as likely, and everybody else says William, so.
9 The spring bloom doesn't have to be smaller, though. One of my plants surprised me last spring with a much bigger show than the fall's had been, because I had unwittingly given it conditions more favorable to blooming.
10 You can fit more plants on a table if they're all growing more or less straight upward from the pot than you can if they're hanging over the edges of the pot, getting tangled in one another. It's also a lot less tricky to slip them into paper sleeves for shipping, and they can be placed on shelves more densely too. Incidentally, I ran into a description of grafted holiday cacti in one source, which described a Schlumbergera grafted on top of a tall, columnar cactus, so that its branches could cascade down around the base without dragging on the table or floor or what have you. If this was ever popular, it's not anymore: I've never seen it in person, and had never even heard of it until I started doing the research for this post. It does sound kind of cool, though. Probably a big pain to ship.
11 I could only find one public domain Schlumbergera picture of a plant with actinomorphic flowers, and the plant in the picture, it turns out, isn't even a Schlumbergera. This is "Schlumbergera gaertneri," which has since been moved to the genus Hatiora. (One source says Rhipsalidopsis, but GRIN says Hatiora, so I'm going with them.) Anyway. These are what actinomorphic flowers look like:
Hatiora gaertneri is neither a Thanksgiving-flowering plant nor a Christmas-flowering plant, but instead flowers in April and is called -- wait for it -- "Easter cactus."
12 They're technically called phylloclades, but I figure since I'm making you read the word Schlumbergera over and over, and since footnote 2 was pretty heavy and probably didn't explain stuff very well, I can be merciful and not throw "phylloclades" around too.
13 Water softeners work by substituting sodium ions for dissolved calcium and magnesium ions. It's not any better to give plants high-sodium water than it is to give them high-calcium water, and in fact it's usually quite a bit worse. Some plants are touchier about this than others, though.
14 It's apparently pretty common for people to water their Schlumbergeras with leftover tea, which is acidic. There is one anecdotal report of a plant which wasn't repotted for thirty-two years, but was given tea leaves as a topdress and watered with only leftover tea, which grew to be four feet (1.3 m) across in a 7-inch (17.8 cm) pot and produced hundreds of blooms at a time. I'm not saying that if you water your plant with tea, you'll wind up with a gigantic plant that has hundreds of blooms, but there's a point in there somewhere about the importance of acidic soil.
15 Though you'll still have fungus gnats, so ponder how you feel about fungus gnats before using Miracle Gro. And also, the usual problems with peat moss -- that it stays wet too long and then becomes water-repellent when it dries -- still apply. Mixing in some perlite is the best suggestion I can come up with for how to deal with peat's tendency to act like peat.
16 One source says 70F/21C is enough to cause pinking, but that sounds really wrong to me: all the other sources more or less agree that they won't even set buds unless they get below about 55F/13C.
17 Yet another point of overlap with Ananas comosus, which is prone to a number of viral diseases that are transmitted by mealybugs.
18 The longer a flower is open, the less viable its pollen is. For best results, you want to transfer pollen within two days of anthesis, which is the botanical term for the moment when the flower has fully opened.
19 Some of the hybrids available are triploids, with three sets of chromosomes: plants with more than two sets of chromosomes ("polyploids") tend to have larger blooms, with wider, more rounded petals, and a more upright habit. Polyploids also tend to have larger, thicker stem segments.
Triploidy makes plants infertile, though (as discussed in the Phalaenopsis profile), so if your plant is a triploid, you're very unlikely to get seeds no matter what plant you cross it with. Some modern varieties have six (hexaploid) or eight (octaploid) sets of chromosomes (Hexa- and octaploid plants have bigger flowers, but aren't common commercially, since they also grow more slowly and don't branch as much.); these will cross with other plants having even numbers of chromosomes, but the offspring may have odd numbers. A diploid (2 sets) plant crossed with an octaploid (8 sets), for example, will yield a pentaploid (5 sets), which will be as much of a dead end as a triploid. So you may or may not be able to keep crossing and re-crossing your plants, and there's no easy, reliable way to know ahead of time how many sets of chromosomes your plants have just by looking at them.
20 "Warm" conditions in this case being a minimum of 64F/18C. Fruit will still develop in cooler conditions, but it'll take longer (up to a year).
21 The yellow variety 'Gold Charm' took its developer, B. L. Cobia, Inc., of Winter Garden, FL, fifteen years from idea to release of the finished variety, during which time more than 50,000 individual seedlings were evaluated.
22 It could be an emergency if: you know it's been many, many years since the plant was repotted, or if the plant was potted in a heavy mix that would promote rot (e.g. if it contained garden soil or fine sand).
23 We were assured that the plants would be treated prior to shipping with a silver compound (I remember it as silver nitrate, AgNO3, but my research suggests that it was probably actually silver thiosulfate, Ag2S2O3, which works by making plants less sensitive to the hormone ethylene.), and that this would keep the buds on the plants. So the first year, we ordered plants from Florida exclusively, and they all dropped buds and it was very upsetting. The second year, we split the order half and half between Florida and a local producer: the Florida plants dropped buds again, the local ones not so much. The moral of the story being that promises from plant wholesalers, even well-intentioned ones, are not always worth much.