Sunday, August 8, 2010

Tease (Schlumbergera truncata cvv.)

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.

Schlumbergera 'Caribbean Dancer.'

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

The natural range of Schlumbergera lies within the states I've (awkwardly) outlined in red. Original map is public domain.

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.

'Caribbean Dancer,' not yet fully opened up.

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 are crazy, obsessive plant people like plants and then ask for cuttings. And even if you don't get Schlumbergera cuttings, friends are good for you!

Or at least sometimes they are. The deeply misanthropic or socially inept can try their luck with eBay or Craigslist or something.

'Caribbean Dancer' again, fully-opened.

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.

Like this plant, I'd say, is definitely saying that more shade would be nice.

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.

A NOID Schlumbergera with pinkish-purple flowers.

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.

Developing buds on S. 'Exotic Dancer.' And yes, somebody really named a plant 'Exotic Dancer.'

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.

One of my personal NOID plants. Bloom looks more peach than anything, but it was supposed to be salmon.

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.

Something my personal plant did a while back; I don't know what the problem was, but I pulled off the affected stem segments and it stopped happening.

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.

This is the best picture I had for showing the stigma and anthers. The stigma is the magenta bit pointing downward at the very tip of the flower; the anthers are just behind it, and hold the yellowish pollen.

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.

Another of my personal NOIDs. I haven't seen this type of coloration very much, where the margin of the petals is a different color than the center. I don't know if that means it's rare, it's unpopular, or I haven't been paying attention, but surely it's one of those three.

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.

'Caribbean Dancer' again. I took a lot of pictures when the plant bloomed last spring, and wasn't happy with the color quality on any of them.

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.

New, developing flower buds.

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:

Apparently this particular segment got hit with a particularly large dose of BA.

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.

Assorted varieties, out of flower.

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) (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) (general care, some history) (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:

Photo by Chilepine, released into public domain. Found via Wikipedia page for Schlumbergera.

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.


~Gardener on Sherlock Street said...

Hello. I was recently given a link to your blog to help me identify one of my house plants. It turns out, it is an Aglaonema
Then, today, I see you're writing about Christmas cacti. I have a true Christmas cacti. It was my grandmother's. We think it is over 80 years old. My mother repotted it before giving it to me as its old clay pot was broke and threatening to fall apart. It has taken a couple of years to get resettled and just started blooming again the past three years. One flower the first year. A dozen or so the next and twice as many last year. I seem to get the blooms just after Christmas and into the new year. I don't "put it away" in a dark room to make it bloom at one time like my aunt and mom did. You've given me a lot of great information about how to care for it. It's a lot of responsibility caring for the "family Christmas cactus." Thank you.

Liza said...

Only 33 pages of notes? Psssshhhht.

Bellen said...

When living in CT I did all the 'in the dark closet' stuff to get them to bloom. Now in FL I have some on the screened front entry facing north, some on the back screened lanai facing south and one on the kitchen counter indirect light from north and south. The one in the kitchen is newly placed the others have been there a couple of years and bloom at almost every end of a branch. They are truly beautiful. I water when I think of it, maybe once every other week. Outdoor temps have been low 90's - high 70's and high humidity, indoor 78-72 with low humidity. I'll have to wait to see how the indoor one does - it has put out some new growth but not like the outdoor ones.

Thanks for all the info, especially about the leaf color.

mr_subjunctive said...

~Gardener on Sherlock Street:

Glad I could help.

From what I read, it sounds like it's normal for true Christmas cacti to bloom slightly after Christmas, unless they're specifically forced to do so earlier. Personally, I figure there's a bigger need for brightly-colored, pretty flowers after Christmas than there is before.


I know, I know. There are 57 pages of notes at the moment for Aloe barbadensis, though, so maybe you'll be more impressed by that one.


I realized this morning when I got the final, official word count that this is the longest single post in PATSP history to date (the previous record was for the Pandanus profile, and this is 1200 words longer than Pandanus), and I probably should have split it up into two parts even if it did mean more work for me. Sorry, everybody.

Pat said...

Don't apologise for putting too much in one post, the more the merrier.

If there were an advantage for the plants that outweighed the advantage of outcrossing to a distant plant then they would probably "cheat". However, the inbreeding that could come from the pollinator visiting the flowers in clumps or going up a tree bringing the pollen of children to their parents would be a great disadvantage. Better to have two seeds with hybrid vigour than three that are inbred. With the vigorous and mobile attentions of hummingbirds I would imagine that outcrossing, the import of pollen from distant relatives, is usually convenient and abundant unless the plants become very isolated.

With up to 300 seeds in each fruit they are obviously hoping to spread widely. Perhaps by a completely different vector, bird, bat or rodent.

This paper gives an example of a tall, columnar desert cactus pollinated by hawkmoths which also has genetic self-incompatibility. Proving that outcrossing has its advantages.

Of course, the whole idea of Lock/Key may now be redundant as some mould/predator may not be present any more but outcrossing is almost always a good thing. Look at the price of F1 veg seed. Though the dandelion appears to have decided not to bother, it is so successful it doesn't need to breed.

Was that tea-fed giant from Britain? I know a few people who only feed their Christmas and Easter cacti on tea.

Jenn said...

I love these posts.

Greensparrow said...

Re self incompatibility and evolution, I say ditto to Pat -- I think the consensus of most people who study it is that self incompatibility promotes heterosis (aka, hybrid vigor) so selfing "cheaters" are out-competed by their self incompatible relatives. Also, as long as there is enough pollen being transferred from other, non-related plants that each flower gets enough pollen to make as many seeds as it can, selfing wouldn't provide any advantage at all. Only in conditions where pollen transfer is a limiting factor in seed production would self pollination be an competitive advantage. A condition which presumably does happen, thereby producing the species which do self.

CelticRose said...

I think the name "Tease" is perfect for this plant. As soon as I read the name, my mind went to all the stories I've heard about this plant's habit of dropping buds. Thanks for the explanation of why they drop their buds when they're moved -- I had alway just assumed that they were prima donnas.

I see these in the stores every fall and winter, but I avoid picking one up because I have my doubts as to how well it would survive our low humidity here in the Arizona desert.

mr_subjunctive said...


I don't know what naturally eats the fruits, but I did run into one warning that ground squirrels really enjoy eating the fruits, and one should make sure that they can't get into greenhouses where Schlumbergera crossing is happening.

The source didn't say where the tea-drinking plant was grown.

I guess what I find puzzling about the whole outcrossing / self-incompatibility thing is that I don't know what the lock and key actually are. If they're DNA or RNA, then having a lock and key that match up exactly is pretty easy -- you could just make a sequence that has a hairpin turn, and then split the RNA at the turn, and you'd be left with two complementary sequences that would match precisely. But then how would the cell "know" that a match had happened? Would the RNA be bound to proteins, too? And if it's made from splitting a single double-stranded RNA sequence, then that means that anytime you make the "Lock," you also make the "Key," in exactly the same place, so there's no way that Lock and Key can't find one another.

And having genes encoding a protein that was an exact match for another protein or for a DNA sequence just, I don't know, it just seems like it'd be too easy for a point mutation to ruin the match. I mean, okay, so hybrid vigor means that any such spontaneously-selfing flowers wouldn't be as sturdy as the regular kinds, but in the short-term, germination of a selfing plant would still be more likely than germination of a SI plant, and if these mutations can screw up the Lock-Key match that easy then self-compatible plants would be arising all the time.

I mean, yes, I get that there must be a substantial penalty for self-pollination. Obviously. The enforcement is what I'm getting hung up on. I didn't run into anything suggesting that the few self-compatible varieties out there are especially weak, which if there was that big of a difference I'd think that it would have gotten a mention.

So I don't know. It's going to bother me until I understand it, though, I bet.


Point taken about pollen being a limiting or non-limiting factor. I didn't get any sense of how dense the natural populations might be, or anything about the quantity and efficiency of pollen being transferred, so I have no idea whether that's relevant or not. But it would explain it, partly. Like I said to Pat above, though, some of my interest is in the biochemistry of it -- exactly what are the "Lock" and "Key" made of, and how does the plant ever manage to produce complementary Lock/Key pairs in the first place?

Nancy in Sun Lakes AZ said...

CelticRose brings up a point I was going to mention. I have been totally disappointed when trying to grow the new hybrids like Caribbean dancer here in Phoenix. The sit around and sulk and eventually pieces start breaking off and they die. Someone got some cuttings of the old original Christmas cactus (my mother-in-law had a huge one 40 years ago) that is Schlumbergera buckleyi. He bought them on ebay from a lady in the Midwest who had a huge old one also. I rooted them and they are doing great putting out lots of new leaves. The plant is in the house now (over 100° every day) but will put out when we get cool again in October. I'm hoping for a great bloom! There is something to be said for the old species and varieties.
I think "Tease" is perfect. I thought of bud drop right away also. I wish I had a dollar for every bud that has dropped--I'd be rich!

Pat said...

The self-incompatibility is determined by proteins encoded by the controlling genes on the surface of the pistil. In the case of the corn poppy this small protein on the pistil is recognised by the pollen surface. If it is an incompatible pollen (i.e. from the same plant as the pistil) a "lock" on the transmembrane protein poking out of the surface of the pollen recognises the "key" which switches on a calcium-ion dependent
signal leading to cell death inside the pollen.

If the pollen is from another plant that is compatible with the pistil the small protein "key" on the pistil does not fit the transmembrane "lock" on the pollen and the kill switch remains untoggled. The pollen then germinates normally.

This other self-incompatibility appears to be different, based on the protein enzyme RNase. Two possible explanations;
a) The Inhibitor Model The pollen produces internal inhibitors to all the varieties of RNase found in the pistils of its species except for the inhibitor for the RNase found in itself. All the RNases are absorbed by the pollen but just the self RNase (if present) kills it by destroying RNA. Like a man never having seen his sister taking antidotes to all the poisons he knows his sister does not use before entering an orgy he knows she may be attending.
b) The Gatekeeper Model The pollen has receptors on its surface which adsorb all the non-self RNase but not self RNase which carries on into the pollen. This again kills the pollen due to its action as an enzyme that rips RNA into small bits.

Which is as far as I can go with that one unless I start reading books. They have discovered such a lot of fascinating things in the last 25 years (since University).

emily said...

i passed this particular article on to many people, you do such an excellent job of illuminating useful information with excellent prose.
i especially appreciate the information on bud drop as i have had this happen many times. i have 3 small "rescues" (the groceries around me sell them after christmas when they're overwatered messes for about a buck) growing like gangbusters out on my back deck now.

ScreamingGreenConure said...

This post is awesome. I now look at my shclumbergera differently!

ScreamingGreenConure said...

I still fail to spell it well, though...

Ivynettle said...

Finally catching up with your posts. Feeling rather fuzzy-brained today, so no intelligent comments, but I find it really interesting that Easter cacti are rare over there - we get loads of them.

Also, I should check on my Schlumbergeras and Rhipsalidopsises on the balcony - been back from holiday for a few days, and I still haven't bothered to do that.

Luke said...

Wow, great article. One of the better resources I've seen on the 'net. A shame you don't have any Schlumbergera x buckleyi, though!

My primary plant is a S. x buckleyi that I'd estimate to be perhaps 40-50 years old (at least). It was my great grandmother's, and when she died in 1975 or so, my dad saved it. He estimates it was perhaps 10 years old at the time. I've had it in my possession for about a year and a half, but lived with it for many years as a kid, and have been growing various cuttings from it since 2004 or 2005 or so.

Sadly, many of the cuttings died in the past year (one seems to have hung on, and I'm trying to hold on to 2 more). They became very limp and had white secretions coming out of their joints. After a lot of worry and head scratching, I *think* I determined that years of using softened water was to blame. At least, I really hope that was the cause. I've been using distilled water for a month or two, and one seems to have picked back up a bit, while I'm hoping the other two might. I have another several (new) cuttings that are doing great.

A few notes... Watering: I've been using a 2-7-7 "Cactus Plus" fertilizer (1 tsp/gallon) year round, and the plants seem to love it. I've never backed off watering *too* much around bloom time, nor have I stopped fertilizing then. With the exception of the aforementioned soft water (hopefully) issues, it has worked great.

Repotting: The "mother" cactus has likely been in the same pot for 10 years or more, and seems quite happy. I'm actually afraid of breaking off a lot of segments if I were to try and transplant. The soil seems to be fine as well...we'll see how things go.

Luke said...


I had a small S. truncata back in 2004, and while it was starting to bloom, I mistakenly left it in the garage too long and a freeze killed it. More recently I've had another small one for the past few years, as well as a larger, more mature one that I received this summer (although still quite small next to the monster S. x buckleyi). Half of the small one had wilting issues this year, but the other half is fine, and I'm hoping that the switch to distilled water will prevent any further damage.

I'm sure I've got more, but here are photos from the past few years. They should be in chronological order, with dates available under "Photo information":

Christmas (and Thanksgiving) cacti

mr_subjunctive said...


Since posting this, I was offered a bunch of cuttings of S. x buckleyi from a reader, which are currently in the basement, where I hope they will root.

I've never heard of a plant with the sort of problems you describe, so I hope you're right about it being just a problem with the water.

Luke said...

Cool about getting some cuttings. I've been putting mine right into a cutting mix, and generally see new growth in a few weeks. One recent cutting has a bunch of new growth, including 4 new segments coming out of a single segment.

I sure hope the softened water was the issue, although I'm slightly concerned since it happened fairly suddenly (just this past year). I've been using softened water since I started growing these. Fingers crossed.

In the fall/winter my dad always kept the big one under a grow light with a timer. So far I've just been going with natural light, in rooms that don't get much use at night. So far so good.

Selena said...

Thank you for your post! I was offered a potted Exotic Dancer just over a year ago from a place I worked at. Instead, I took 2 sections and figured someone else could have the rest. I took a pot that I had tried numerous times to grow chives in, put it in the freezer to kill off anything, and once it had warmed up enough, I put the clipping in. I got it to root... and even got some chives! (chives are jerks. 3 freaking times I planted seeds. I just figured my old seeds were bad. I guess all they needed was time to "chill out") I did have a problem with gnats or something but that's since cleared up. It also survived my mom's visit in June when I was staying at the hospital with my newborn for a week and mom killed off half my plants (WHY did she put them all on the back porch steps and WHY did no one think to water them?!?! BAH!)

I decided to google the care, because my friend made a comment this weekend about how the tag says to keep it in indirect sunlight, and I've got it in a window. I told her it was a northern window that did not get direct sunlight and she argued with me (I still think I'm right. So there!). I figured I hadn't killed this thing, I should know more about it.

Thank you for this. You wrote the best care article I found!

Luke said...

Following up from last year...

My large buckleyi (which I think we're now estimating at 50-60 years old, at least) is doing pretty good, although a few sections seemed to rot away over the past year. So far the rest of the plant seems healthy though.

Last winter I did some cross pollination, between my buckleyi and two (I think) truncata varieties. About a month ago I harvested a handful of the seed pods and planted the seeds. I now have a few handfuls of sprouts. I'm not sure if this is all I'll get or if more will sprout over time. I wasn't too careful about washing off the goop from inside the pods.

Unknown said...

Hey,I'd have a question about our christmas cactus,it's not seeming to absorb water very well,the ends of each leaf has gone pinkish red but no flowers,it has always been green and only have the pink flower but now the plant is turning that redish colour.We water it but it's still wilted.What's causing this?

mr_subjunctive said...


It would probably be easier for me to take a guess about what's going on if you told me something about how you're taking care of it. How much light is it getting? From what source? How do you decide when to water? How much water do you give at a time? What temperature range is it subject to? Is the coloration on the new growth more of a bright pink, or a dull red? How long since it was repotted? Has it ever flowered? How old is it? Etc.