I WAS SCROLLING through Instagram the other day—yes, sometimes I just can’t help myself—when I saw a post by Matt Mattus about Christmas cactus. So even though it’s still high summer, it made me long for one of my own.
I haven’t grown a holiday cactus since my very old plant took a nasty spill in a move of houses years ago. Seeing Matt’s post also made me think it was time for a review of how to get those lavish bloomers to do their colorful thing, and that was what I asked him about when we spoke recently.
Matt Mattus gardens in Massachusetts and is the author of various garden books, including “Mastering the Art of Vegetable Gardening” and “Mastering the Art of Flower Gardening.” When he isn’t tending his own ambitious garden and greenhouse or hosting Open Day tours, he also provides consultation services, both virtually and in person, to help others with garden design and plant-care issues.
Read along as you listen to the Aug. 19, 2024 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify (and browse my archive of podcasts here).
holiday cactus help, with matt mattus
Margaret Roach: Hello, Matt, in this craziest of garden years ever.
Matt Mattus: And we’re going to talk about Christmas cactus.
Margaret: I know. What the heck? We’re just going to forget the rest of summer, Matt, and talk about Christmas cactus. So before we do, tell the truth, how many, quote, “houseplants” do you have?
Matt: Well, that’s a really liquid topic now because you know I have a greenhouse, so-
Margaret: I know.
Matt: We built the greenhouse so we didn’t have to have houseplants, but then gradually they moved back into the house. So we have a lot, let’s put it that way.
Margaret: Is it 88 million or 3 trillion?
Matt: Yeah, maybe half a million.
Margaret: I had a feeling. How many Christmas cactus or holiday cactus do you suppose you have?
Matt: Oh, holiday cactus. Not a lot. Maybe 10 or 12 right now. Just inherited a big old one, so we’ll talk about that.
Margaret: O.K. So I say “so-called,” or in quotes “Christmas cactus” or whatever, because I’ve lost track of the taxonomy frankly. I know there’s a lot of hybrids now that have been bred, and I don’t even know how you pronounce it, but it used to be Schlumbergera [laughter]. Schlumbergera. Then there was x buckleyi and the other thing was the Christmas cactus in truncata. The species truncata was I think the Thanksgiving cactus. Twenty years ago, I used to know what was supposedly the taxonomy. I am lost now [laughter].
Matt: You’re not alone. Put it that way.
Margaret: O.K., good.
Matt: I’m lost, too. And in fact, doing even more research and the more I look, I’m learning that a lot of the experts are lost too. I mean, even the Latin … So the genus name is Schlumbergera. So everyone for over 100 years now have been calling it Schlumbergera.
But I just read something the other day that he was supposedly from Germany, but now they believe he was from Austria, and there’s an Austrian with a similar name that they’re not sure now who really named it after whom. It was named after a collector, but it doesn’t really matter.
Margaret: And you said Zygocactus in your recent Instagram post, which I also have read is some people call the genus that, so whatever.
Matt: Yeah, it was. The genus was named Zygocactus in the middle of the 20th century. And then it is pretty much organized now. But again, for the home grower, you don’t need to know this, we tend to put them in buckets by holidays, like Thanksgiving cactus, let’s say, Christmas cactus, and then Easter cactus, kind of the outlier. And that’s, I think, an easier way to lump them all together. You can get lost in the Latin name for all of these.
Margaret: So cactus, the other word—these are not desert dwellers. These are, I think, epiphytic plants, generally speaking, that are from the mountains of Brazil, like a rainforest environment, I think?
Matt: Exactly. And that provides a tip for all of us who want to grow them. They are indeed Cactaceae. So they are succulents, they are cactus.
Margaret: Right.
Matt: Which throws so many of us off on this loop. And that’s why I’m glad you called to talk about this because it’s such a common houseplant. And I don’t know about you, but I grew up with my mom’s plants that were from the 1920s.
They were my grandmother’s, so they were often hand-me-down plants. And I bet there are a lot of people out there that have these older specimens. And the more I learned about them, I don’t know if they ever fell out of fashion, but they’re always out there. It’s not one of those plants you can go buy a silk one at a craft store at Christmas [laughter].
And there’s some beautiful colors now. And I think we’re tempted when we see them at the supermarket, or nursery around the holidays. So I thought I would just revisit them again to see what I could learn. And I was kind of surprised; they’re abused in my house. Are they going to bloom the holiday season or not? Or are they not going to bloom at all this year? And then once they bloom, we kind of ignore them until summer, when we throw them outside. And I bet a lot of people just do that, right?
Margaret: Mm-hmm. So what do you think, though, with your 10 or 12, and with your various years of experience with them, what do you think? And in the Instagram post the other day, you outlined your basic recommendations, but what is your method in the best of times? I mean, we all fall off the protocol from time to time, but what would you say, and where are the pitfalls? Where do we want to start?
Matt: Well, a lot of this started with when I built the greenhouse. So I have a cold greenhouse that’s not heated, but you don’t need a greenhouse to grow these plants. But the greenhouse taught me something about these and Clivia, oddly enough.
Margaret: My favorite houseplant. Yes.
Matt: And the biggest complaint with both Christmas or holiday cactus and Clivia is how do I get it to bloom? That problem was solved for us when we built the greenhouse because we kept the plants out there. They didn’t go dry. All the myths that surround all these very common houseplants, watering them with milk or cinnamon or whatever.
Margaret: I hate all that stuff [laughter].
Matt: And it’s so confusing. Put coffee grounds. So don’t put coffee grounds, make the soil more alkaline. And these are plants that want acidic. I knew my mom only grew these in soil from the garden, which I thought was crazy, until recently I’m realizing that that’s not a bad idea, to mix regular ground soil in with your mix. These are not heavy feeders. These are not plants. They’re jungle plants, like you said.
So what I like to do first is look back where they’re from. So the greenhouse for me is cold and wet in the winter. It seems like they wouldn’t like that, right? They don’t like cold temperatures, but they would come into the house when they set buds. But the big thing was they started setting buds naturally by October. And I never knew why. And same thing with the Clivia. They always bloom in March now, all of them, without any care at all. It’s all because of they respond to day length, right? They’re-
Margaret: Right. We’re triggering that by allowing them to, in your case, it sounds like they’re cooling off in there for a certain period.
Matt: They’re thermo-periodic, so it’s temperature and the length of the night really. Some people say day length, but they need those … Like right now we’re all starting to feel like, oh, maybe it’s fall in the air, right? The cyclamen is starting to bloom. We’re starting to want to braise something on the cold days.
And by September, if your plants are outside, they sense that the days are getting shorter. So Christmas cactus or any of the holiday cactus, or not the Easter cactus perhaps, but the first two, let’s say, let’s group them as Thanksgiving and Christmas, that should all be setting bud outside in September. And by middle of October, they should all be showing buds. If you’re indoors, you need to get them into a room where they’re getting natural light and not even a street light outside, and not even a light or lamp in the room.
Margaret: I’m glad you said that because when I was taught about them, and this goes back decades, and it was like, “And here’s how you should take care of it, Margaret,” I kind of inherited the family one, and it was all about 14 hours of darkness a night to simulate … And it was like a lot of people said eight weeks of that. And some people said only four weeks would even trigger it, it would be enough. But it was like eight weeks of 14 hours a night. And again, this is old advice and I don’t know what the current protocol is.
But the idea being like with the Clivia, where I keep them much cooler and dry, to sort of say to them, it’s time to think about getting ready to flower, it’s time to think about getting ready to flower, simulating something that in their ancient roots, in their homelands, there was a period of this whatever, deprivation of some element [laughter]. And it triggered it. So I would be simulating it. And that’s what I always did with the holiday cactus. And I used to read about in old garden books that we’d talk about, you’d put a black plastic bag over them at night or something for 14 hours, set an alarm clock [laughter].
Matt: My parents would bring them in the fall and put them in the cellar windows. I remember that. And they would always bloom. So yeah, there’s something to that. I think we have to remember they’re from Brazil and that’s the Southern Hemisphere. So they bloom in May. So I think it’s like Florida mayo or something, called the Flower of May. So it’s like many South African or South American plants that, they’re on the opposite schedule up here in the North. So conveniently, they bloom early winter.
But here’s an interesting fact. The Christmas cactus that you had, or let’s say the holiday cactus you probably had, if it had the rounded leaves or clads, the sort of paddles, right, on the stems? That’s the old Christmas cactus. It’s not sold anymore. You can’t find that at a garden center or nursery. It is truly a pass-along plant. All the ones you find now grown retail are technically they’re Thanksgiving cactus. It’s the cross. I mean, the old one was, yeah, you were saying the Latin names before, which-
Margaret: Well, one is now they say with the Christmas, they say x buckleyi and truncata was the one that they used to say was Thanksgiving. And I don’t know what the original species was of the, as you say now, not in commerce, the original Christmas. I assume x buckleyi means it’s a hybrid with something else, but I don’t know.
Matt: No, you’re right. Christmas cactus. I mean, they go back to the 1830s when they were first introduced. It was Epiphyllum x buckleyi for a while, which also gives us, you know, that’s the orchid cactus. So these are all plants that in the wild, again, going back to look for culture, how we can grow them, look back to where they grow in the wild.
They grew on mossy branches with leaf litter in Brazil, in a cloud forest. Definitely not cactus environment, but they were well-draining. That tells us they like, so that’s really well-draining, like an orchid. They like moisture around in the air but not around the roots really. They don’t have strong root systems because they are epiphytic or lithophytic, meaning they sometimes grow on rocks, but on cliffs.
So those are all tips that we can use. And they love acidic soil or acidic rain. So all those, that tells us what kind of water they want, what kind of nutrients they want. And combine that with the daylight thing, you have these things nailed. Now it’s how do we do that at home?
Margaret: And if we want to actually have it for a holiday, i.e.Thanksgiving or Christmas, you’d have to back up to right around now and say, “Hey, guess what, honey, you can’t be out on the porch anymore in the bright light. I’m going to deprive you of that for 14 hours today.” [Laughter.] You know what I mean?
Matt: Yeah, yeah.
Margaret: You’re going to probably shift their position. Or like you said, someone in your family used to bring them into the basement, into the cellar window.
Matt: I think frost came, or at least here in Massachusetts, frost arrived earlier.
Margaret: Oh, for sure. In September for sure.
Matt: We could still get one in September. But to really guarantee you’ll get buds, I mean, using my greenhouse example, I leave mine out as late as possible until that first threat of frost, which there might be a night or two in September I have to bring them in. But they go back out again. Because that’s when they’re really sensitive to the day length.
So right now they could set buds by the end of September. You’ll look carefully. And once they set buds, then you can treat them differently. But we reach that, it’s 13 hours actually is the recommended length of the night, but it’s probably 12 to 13. And I just keep them out until early October maybe, and then bring them in.
Margaret: And so you’re bringing them into the greenhouse, but let’s pretend we don’t have a greenhouse. So you were talking about a lot of different things, the soil and the acidity and the good drainage and things like that. So what would be ideal for me to do with, if it is my houseplant, what do you think? What should I be doing with it this fall?
Matt: Yeah, let’s go through the whole calendar of what you would do. It’s pretty simple. I bring them in whenever that first heavy freeze will be, so it might be Halloween. If they have buds on them already, I bring them in the house, I bring them onto our windowsills. We have deep windowsills, so they’re almost on display at that point because they’ll bloom probably for Thanksgiving or between Thanksgiving and Christmas. The 12 plants tend to bloom week on, week off up until then.
Once they bloom, the season’s over. So most are done by, let’s say by New Year. The problems people have then is sometimes you get bud drop, and that just happens when the temperatures shift too much. But what I’m talking about is if we had 90-degree days and then suddenly 40 degree days, they don’t like that. Or if they’ve gone too dry when they have this. Just keep the moisture sort of even, not soaking wet. Always remember they don’t have big root systems. They want a really porous soil. So either lots of perlite or lots of gravel in the soil.
Margaret: You talked about a barky mix in your Instagram post; that bark may help, too. Whereas it would still have fast drainage from the other ingredients in the potting mix, the bark might hold a little bit of moisture for them to utilize with their small root system and so for them to sort of hang on to. So almost like orchid bark, that kind of bark a little bit in the mix?
Matt: Yeah. I use a fine orchid bark from a wholesale grower. The really good wholesale growers will use fine orchid bark, maybe 50 percent. And the other 50 percent is either a commercial potting mix or coir and perlite. So it’s very fast-draining, almost like what you have your phalaenopsis in, but with a little more potting soil in it.
Margaret: And not swimming in a giant pot. These are guys, they don’t need, because again, these are, a lot of them are like epiphytic almost. They’re like hanging in trees and so forth, resting on. So they don’t need a giant pot.
Matt: No, but they need a heavy pot. So I tend to use clay. If I don’t use clay, I put a rock in the bottom of a plastic pot. Because you know how top-heavy they are, they can swing around and fall over.
Margaret: Well, that’s what happened to mine. And I was moving between one house and another, and it took a spill and it kind of shattered and it was a mess, my old one. So yes.
Matt: The other tip I learned recently was to pinch them back. I had never pinched holiday cactus at all.
Margaret: Oh.
Matt: But in January, February before the new growth starts, and commercial growers grow them in one season, so it’s always good to look at the commercial grow sheets for tips. So you can just do a Google search for culture sheet for, they still might call them Zygocactus, some growers, they might call them Schlumbergera or holiday cactus, but you’ll see what the professional greenhouses use.
And you may not want to use the chemicals they’re using. You may not want to use the soil. So they’re using a lot of peat because they want to make a highly acidic soil. But they do teach you some good tips. And that one tip of pinching was something I learned there, that we see so many buds on the ones you buy at the market, it looks like they’ve been treated with chemicals, right?
They pinch the tips out, the first new growth, and then they get more clads coming out, more leaves, if you will. And then all those produce more buds. Just don’t pinch after March.
Margaret: So pinching. So the “clads” [cladodes or cladophylls] are these segments that make up what look like a bunch of leaves stuck together, or stems, depending on how you want to think about it [laughter], the branches, so to speak, but pinch out a whole one. Am I taking a whole one? How far do I pinch?
Matt: One leaf off, let’s say. Follow the tips. They might send out three new ones. And then fertilizer is interesting because these are, and you’ll see, don’t follow anything of the myths for fertilizer. You certainly, they’re not going to feed these milk.
Margaret: Oh, please. If the internet doesn’t stop telling people how to kill plants, I swear.
Matt: The more common the houseplant, I think the more myths there are.
Margaret: Torture. It’s torture. It’s all torture [laughter].
Matt: They want acidic soil, so you’re not giving them coffee. I’ve seen that too. Because it’s not really-
Margaret: Oh, please.
Matt: Yeah, they want rainwater. So start with the basics. They want acidic water. So if you use tap water.. I never knew this, but I checked our tap water here where I live and the pH is really high because it’s been, even though we have acidic rain and acidic soil, the city, and most city water is adjusting the water pH. And it doesn’t affect the plant over a few months, but over a year or two or three, and you’ve never re-potted it, that soil has become really alkaline. And then you see these sort of shriveled up, crisp holiday cacti that are struggling.
So it’s probably best to re-pot it every year or every two years in a new acidic mix. And March would be a great time to do that or April, and reintroduce in a good mix. Like I said, a really porous mix, like a half orchid bark mix. Even if you just half orchid bark, half potting soil, that would be great. You might want to add gravel or a couple handfuls of garden soil in. That is one myth I’ve seen that seems to be proven by a lot of cactus and succulent societies. I haven’t researched it, but hey, my mom did it and it worked [laughter]. I don’t know if that’s any reason to try it, but my plants are looking pretty amazing now. They’re getting rain. This has been a great rainy summer for them.
Now that they’re in new mix that’s fresh and acidic, and they’re getting lots of new green growth, and I’ve been fertilizing with a half-strength fertilizer. But there’s two things with fertilizer they don’t like. They don’t like iron. And that’s really important, because if you’re using any commercial brands, like anything that’s blue, that’s water soluble, it has iron in it. So they are a lot like geraniums. You know how hard it is to grow a geranium and fertilize it and it doesn’t look like the one you bought at the garden center in the spring? There’s a feed called geranium feed that the professionals grow in, and it doesn’t have iron in it, but you can never buy it retail.
But now with the whole cannabis industry, these little startups are selling specialized soils for cannabis growers, because they’re crazy about what they’re feeding their plants
Margaret: And specialized fertilizers then, as well?
Matt: And it’s a trend I’ve seen recently. I just went onto Google and I found a few growers that are actually selling Christmas cactus fertilizer. When I looked at the analysis, it doesn’t have any iron. So they don’t like manganese, either. So I thought that’s pretty smart. And these are in one quart containers. So it’s affordable. It’s a really weak strength.
Be careful sometimes with seaweed fertilizers or any fish emulsion, because they’re too high in nitrogen, but most of them are like a 2 or 3. I mean, you’re fine. These aren’t heavy eaters, but they do want some food during the summer growing season.
Margaret: O.K.
Matt: But just not iron.
Margaret: And light-wise, again, these are not cactus in the desert, baking in the sun. We don’t want to, even in the summer, I’m assuming you don’t have these out in the hottest, most baking spot in the garden. Are these in a bright, filtered-light situation or what’s their, because they can kind of burn, as I recall.
Matt: Absolutely. If they grow on trees in the jungles, you know they’re getting dappled light under the leaves. So if you could look for those conditions, it might be the north side of your house where it’s open to the sky, but the sun never hits.
They don’t want to be too dark, though, because they still need to photosynthesize. Underneath a magnolia or something like that would be too dark. I have us on a deck, they’re underneath, they get shaded by a big Stewartia that sort of lets dappled sun down onto them. But they’re not getting, they get little dots of suns kind of wiggling around on their leaves, but they’re not getting full sun. Yeah, you’re right. They will burn very easily.
Margaret: Yeah, I remember that sometimes the tissue almost gets red like sunburn before it really deteriorates. You can almost see when they’re getting damaged, about to get damaged or starting to get damaged.
Matt: Or turn purple, turn purple.
Margaret: Purple. Right. Right. Exactly.
Matt: Especially they’ll lose that once they start getting into kind of a less, the intensity of the sun is less.
Margaret: Right. Unless you leave them out in it too many days in a row, which would be bad. Bad, bad, bad.
Matt: We’ve all done it.
Margaret: Yeah. So the other thing I was curious about is, as I said, my old one had an accident in the moving van situation, fell off [laughter]. Anyway, it was a disaster, busted up into pieces. Of course I probably could have propagated. How easy are these guys to propagate?
Matt: Oh, they’re very easy. I mean, this is why they’re such a great pass-along plant. You could take a cutting again in March probably when you’re doing pinching. So if you wanted to pinch, you could pinch back three leaves worth. So three or four of those clads or leaves or those cladophylls, you would pinch off. And I wouldn’t root them in water. They’re really best rooted in a really porous mix, just perlite, even in a yogurt cup or in a drained container, but water it every day so it runs through, or a little bit of soil and something really porous like aquarium grit.
You could buy a cactus mix and then add some potting soil to it. That’s good, too. I think the test is if you pour water into your mix and it runs through, but you feel the mix and you feel dampness, that’s a good mix. And they root in three or four weeks.
Margaret: Oh, O.K. All right. Good.
Matt: Speaking of cuttings, the ones you buy commercially now, also, they put like 30 cuttings in a pot. They want to get a beautiful plant that’s probably, they intend it to be disposable. So they’re putting, I don’t know, 12 cuttings in a three inch pot.
Margaret: So a real quick bulk up, sell it, the end.
Matt: That’s not a healthy way to grow it on. So if you do get one of those around the holiday season, I would at least split it into two or three. Ideally, three plants to a pot would be great. And that would be a smart thing to do if you want to get an heirloom plant.
I mentioned I inherited, my mom had these old plants. My mom, she had me, she was 45, she died at almost 100. And I have these plants that are probably 80 years old, but I lost them all and I was devastated. But my godmother, who lives across the street from us, passed away this spring. And we went over to help clean the house out. And there was one of my mom’s Christmas cactuses on her windowsill, and it was just as old as the ones we had. So I was so treasured to get it, but it was in pretty bad shape because no one was taking care of it. So I just re-potted it and it kind of fell apart. But in this new soil mix, I mean, these plants are older than a lot of humans, right?
Margaret: Yes.
Matt: We corky and we cut it back and it’s all regenerated, and it’s pretty exciting to see that happen. But it’s that old-fashioned one. It’s the old buckleyi that has the rounded clads. It’s scalloped on the edge of the leaf, and it has a beautiful bright pink flower. But I mean, is there really a bad holiday cactus?
Margaret: Yeah. Well, we’ve used up our time almost. And so I was going to say, you just remind me, because I have my grandmother’s Clivia, which has got to be 80 or 90 years old. I mean, it’s now many, many plants, but the same kind of thing, where it’s just such a treasure and it’s your most precious thing. So I love that you found part of your mother’s Christmas cactus. That’s fantastic.
Matt: And the care is the same on both of these, too. So if you’re struggling with Clivia, we just answered that question too.
Margaret: Yeah, yeah, exactly. Right, right. A little tough love for a while there. Yeah. Well, I’m glad to talk to you, and like I said, I was glad to see it. It made me want one again, and so maybe I’ll be going out doing a little shopping. But it’s always good to talk to you, Matt, and thank you. Thanks for making time today.
Matt: It’s a pleasure. Have fun choosing one of the 2,000 varieties that are up there.
Margaret: [Laughter.] I know. It was easier in the old days. All right. I’ll talk to you soon again. Bye-bye.
(All photo by Matt Mattus, used with permission.)
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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 15th year in March 2024. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the Aug. 19, 2024 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify (and browse my archive of podcasts here).
