Episode 187: snake plants aka Sansevieria

Colin Walker’s Sansevierias on display. Photograph: Colin Walker.

Colin Walker’s Sansevierias on display. Photograph: Colin Walker.

Transcript

Episode 187

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Jane: Hello and welcome to On The Ledge podcast and this week we're charming snakes - the plant kind. Greetings, listeners! My name is Jane Perrone, I'm the host of On The Ledge podcast, the houseplant podcast that takes you deep into the world of plants in your home. In this week's episode, I'll be chatting about Sansevierias, aka the Snake Plant, those wonderful, tough succulents, with expert, Dr Colin Walker, and I'll be answering a question about repotting hesitancy.

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Jane: Ellen, Margot, Caroline. What unites these three people? They've earned themselves a place in my good books for becoming Patreons of On The Ledge and it is this band of more than 300 people who really help to keep the show alive, so thank you to those three new Patreons this week! If you want to find out how to join them, just check the show notes at janeperrone.com and thanks also to, I don't know how to pronounce this, is it NanKatieDid or NanKatyaDid? I don't know! Anyway, you're from the US and you wrote a lovely review for On The Ledge, so thank you to you!

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Jane: Snake Plants, aka Sansevierias,are the Mr T of the succulent world; chunky, funky and oh so tough. They are something that I've been wanting to delve into on On The Ledge for many a moon and finally, this week, it's happening. I'm bringing back Dr Colin Walker, President of the British Cactus and Succulent Society, biologist and expert on this genus, to talk all things Snake Plant, from propagation and pollination, to that taxonomic controversy. We'll cover it all.

The taxonomic controversy, I'll just preface that by saying that I'm still calling Sansevieria, Sansevieria, despite the fact they've now been placed into the genus Dracaena following genetic research into their DNA. As we'll hear from Colin, it doesn't have to spoil our fun of this wonderful group of plants which really do make a fabulous addition to anyone's houseplant collection, so without further ado, let's get cracking and hear my chat with Dr Colin Walker.

Colin: Well, hi folks! I'm Colin Walker. I'm currently president of the British Cactus and Succulent Society but my eight-year presidency is just about to come to an end. I have been interested in growing and studying succulents for just over 50 years. I'm now retired, so I can spend more of my time looking after them, growing them and writing about them. I have a large collection in two greenhouses, a conservatory and a porch. I currently live in Scotland, just north of Glasgow, so the growing conditions are a bit challenging to what I was used to in Bedfordshire.

Jane: We're here to talk about Sansevierias and this has been a subject that people have been requesting, pretty much, since day dot of making this podcast and we're finally talking about them, devoting a whole episode to them, and these plants have grown hugely in popularity in the last few years, but I wonder whether you could start off by telling us a bit about where and how they grow in the wild and what conditions are like? I'm guessing they have to be tough because they're from a place where they're not getting much moisture.

Colin: Sansevieria is a genus of about 80 species, mainly distributed in Africa. Also, there's a couple in Madagascar then, going east, they occur in Arabia and as far east as Burma - there's a Sansevieria burmanica. I've only ever encountered Sansevierias in the wild once. We were on a safari in the Eastern Cape province of South Africa and there I encountered what I believed to be Sansevieria Hyacinthoides. There are about five species native to South Africa and this was growing in, I would say, sort of grassland, really, so it wasn't a particularly arid environment. In fact, the Eastern Cape province is quite moist, to be honest. So the southern species don't really occur in particularly arid environments, but going north, if you go north west into Namibia, Angola and then going northeast through Kenya, up into the Arabian Peninsula, obviously conditions get more arid. They will grow in very arid environments there, where the rainfall is very low, so they occur in quite a range of habitats. They are tough, they are very tough plants, so they can survive extreme environments that are very dry, but also some of them come from very moist environments as well, so that kind of relates to the way we grow them in cultivation. They're tough beasts!

Jane: I've seen a division of - I don't know where I read this. I think, actually, it was in a book that I've got in electronic form only by an American writer called Hermine Stover, does that name ring a bell? - and I think it was in there that I read that she classifies them into soft leaf and hard leaf forms.

Colin: I would use a different sort of breakdown. The soft-leaved ones I would call them thin-leaved rather than soft-leaved because, to be honest, all Sansevierias have got tough leaves and they're tough because they're full of fibres. They have been used as a source of fibre commercially, it's called bowstring hemp, so the same way that Agave sisal**ana is used as a source of sisal because Agaves are very fibrous. Sansevierias have, in the past, been used as a source of bowstring hemp fibres, so all Sansevierias have tough, fibrous leaves. The kind of commonly encountered species, trifasciata, it has a long, thin, strap-like leaf. It's not very succulent, it's quite thin, but it's very fibrous, so that's the one end of the spectrum. The ones that I particularly like are at the other end of the spectrum, which have very fleshy leaves. They're still quite fibrous but they're very succulent. So if you cut a section through some of these leaves, it's circular in section, or deeply channeled, so they are very succulent. So that's kind of like a crude division, so the thin-leaved ones and the very fleshy, much more succulent-leaved ones and in terms of succulent enthusiasts, it's the really succulent ones that are more interesting, and in some respects more challenging to grow, because they tend to be slower growing.

Jane: Obviously, they're very fibrous. Does that mean that not much actually eats them in their native homes? I'm thinking, I've got some phrase in my brain, god knows where it comes from, that is "elephant's chewing gum", which possibly indicates that elephants eat them, but I don't know where I'm getting that from?

Colin: I have no evidence for elephants eating Sansevierias. I've never read anything about that. To be honest, I can't imagine elephants eating these things because they're quite tough and the thin-leaved ones don't have much moisture in them. Elephants tend to like fleshy plants. They're renowned for eating baobabs, for instance, because they are very fleshy, so I can't imagine elephants eating them, to be honest. In terms of animals eating Sansevierias, I wouldn't have thought there's much danger of that, certainly in cultivation. I find Sansevierias pest-free, to be honest. My cacti and Crassulaceae are quite prone to mealy bugs - that's a common pest of succulents. They don't seem to attack Sansevieria so, in terms of pests and diseases, Sansevierias are pretty trouble-free in my experience.

Jane: Yes, I don't think I've ever had a pest on any of mine. I can't recall having one. I'm sure there's somebody, somewhere, with a Sansevieria with mealy bugs. Interestingly, these plants are often classified as un-killable, but I'm often a bit concerned that people suggest putting them into: "Oh they're very good in deep shade," which seems counter-intuitive to me, given where they come from and that they are succulent plants. If you actually want your Sansevieria to really grow and thrive, what are the best conditions for it?

Colin: I have only ever killed Sansevierias when accidentally, it wasn't accidentally, they were in a greenhouse and accidentally the greenhouse heating failed, so I had no heating for about five days in a greenhouse and I lost only six Sansevierias. They were completely killed, they got frosted. So the first point is Sansevierias make ideal houseplants, they love warm conditions. So I have virtually no Sansevierias in my greenhouses. All my Sansevierias are either in the house as houseplants or in the conservatory and I guess nowhere does the temperature ever drop below 12C. Obviously higher temperatures are good, so they love centrally heated rooms, so that's the first point - higher temperatures - they do not like low temperatures. They do need light. They're plants, so they need light, but they are tolerant of low light conditions but they won't grow as well, so they will survive shade but they won't grow so well or they probably wouldn't flower. So I have most of mine in a conservatory that's got a plastic roof, so it is dappled light but there's a lot of good light but it's not full sunlight, I would say. Really strong sunlight could damage them. I suspect that I've never had that trouble either. So, grown as houseplants, I would advise give them as much light as possible. Sunny south-facing windowsills are probably best if you if you've only got windowsills. They make perfect conservatory plants, so long as you heat the conservatory during the winter. So, as good a light as you can give them, warm temperatures and, now, when it comes to watering, this varies a lot depending on the conditions. I grow mine in a mixture of two parts John Innes, one part grit, so it's fairly free-draining and I water all my Sansevierias modestly, once a week, all the year round so I don't stop in the winter. My friend Gordon Rowley, who's no longer with us, used to grow his on the windowsill and he used to have saucers under his pots and he used to keep water the saucers 24/7. So for a lot of Sansevierias they can take a lot of water but it does depend on having a really free-draining compost. If you just use John Innes or one of these standard horticultural mixes with no grit or added drainage they can rot off if you give them too much water and, to be honest, a lot of houseplant growers do tend to over water. So I guess my advice is modest water, once a week, if you're growing them as houseplants and they thrive under those conditions. The other side of the coin is they can thrive on neglect, you can go away and leave a Sansevieria for a month. If you go off on a summer holiday and you're away for three or four weeks, you can leave them with no water and they will be fine when you came back. So they do survive on neglect, but they do thrive with a bit, or shall we say minimum, TLC.

Jane: It's an interesting point about the potting mix. I think that lots of people buy these plants and the way they come, often from the Dutch nurseries, is in a mix that's fine for them in the Dutch nursery but, when you get them home, is just too moisture-retaining. So I always say to people, "Well, have you repotted it yet?" because I think that mix, if you water generously, just keeps too much moisture around those roots. They are quite amazing, the roots of Sansevierias. I don't know if all of them are orange, but I certainly know that a couple I've repotted recently have had lovely orange roots, which was kind of interesting.

Colin: It's not just a root system. It's an underground stem for most of them, so what you're describing as being orange isn't actually the root, it's the underground stem. So they have some very thick underground stems called rhizomes. It's a bit like an iris, to be honest: most of the stem is actually buried underground and what you're saying is orange, is actually the stem. Some of them need a lot of space for that. I got a plant that was collected in Tanzania last year and the leaves are about 10/12 cm long but the plant, because it's got this big, thick, chunky underground rhizome, needed a pot that's a good 15 cm tall. So most of the plant is like an iceberg; it's underground. You can actually use that to propagate them, so I guess we'll come on to propagation later on, but we're talking about roots at the moment, so those underground stems, you can take sections of those, chop them up, take sections and plant them and they will send out shoots. The other thing, while we're talking about roots and potting compost, is quite a lot of Sansevierias don't like being disturbed. They don't like their root system disturbed. So what I tend to do is leave them alone in the pot until they're absolutely pot bound and then repot them because it can take several months for them to kind of establish in their new pot when you've repotted them.

Jane: That's an interesting point. I've had the experience of finding a plant that's been inside a plastic pot and then in a cachepot and I've lifted out the inner pot and discovered that it's literally busting out of the inner pot because they get so huge and I guess that's the secret to their success of being able to be very tough and they're storing a lot of water and nutrients in that rhizome.

Colin: I tend not to use plastic pots very much for Sansevierias because I'm growing them indoors, so I want them in attractive pots. I have occasionally had plants burst through a plastic pot because there's so much underground growth. Yes, they'll burst through, absolutely, yes!

Jane: There are loads of different Sansevieria species on the market now, absolutely loads of them. I was just looking at some pictures recently of the Whale Fin Sansevieria, Sansevieria masoniana, where they're selling them with etchings. They've somehow marked the leaves to make a picture on the side of the leaf. Did I send you a picture of that?

Colin: Yes, I hadn't seen that before so thank you for that. It's like these garden centres that sell cacti with dried flowers stuck into them. It's not natural, is it? I hate that kind of thing.

Jane: No, it's very strange. I don't understand what the rationale is, but I guess they're selling plants and somebody's buying them! There are so many different species that are popular now and also, I know you're not that keen on variegation, but the variegated forms are popular. I recently got hold of my dream Sansevieria, which is Bantel's Sensation. I've been reading up on, it that it's actually quite hard to grow, relative for a Sansevieria, but so far so good on that one. Do you have to be careful if you're trying to propagate a variegated one? Will it grow true from a rhizome division? Will the variegation stay?

Colin: If you want to talk about propagation, just generally, there's four main ways of propagating Sansevieria. So the slowest process is growing from seed. I have never done, that to be honest, and seed isn't very readily available, so that's kind of a specialist way to propagate Sansevierias. The easiest way is to take cuttings. So some plants, like Sansevieria parva**, form very large clumps and you can just take offsets, cuttings. Parva is one that produces overground stolons, so it sends shoots along the soil surface and you can just take one of those shoots and they'll re-root quite quickly. So dry off the surface for a few days and pop it into some compost and that will take quite easy. We've already talked about the underground stems, the rhizomes. So you can just take sections of those and, again, dry them off before you put them into compost and they will root and shoot. The final quite easy way, although it's quite a slow process, is to take leaf cuttings. So, Sansevierias come beautifully from leaves. You can take a leaf of one of the really succulent ones like C**ylindrica, so you could have a leaf that maybe is 30 cm or 40 cm long, you could actually chop that up into half a dozen bits and each bit will root, but it's quite slow. Sometimes it takes six months, even a year, for a leaf cutting to root and maybe even another six months before it will send out shoots but, eventually, we'll get shoots from these leaf cuttings and I have had virtually zero failure rate with that. The question you asked me was about the variegates. Now that is slightly tricky. Variegation is quite a complex process because you've got different layers, with different cells. Quite often what happens, if you take a cutting off a variegated Sansevieria, it's the lean part that will send out shoots and the variegate doesn't. So if you've got a variegated Sansevieria, really you shouldn't be trying to propagate it from a leaf. You need to take it from a shoot, or if it's got underground rhizomes, you can take sections of that which will root. So, a variegated Sansevieria will propagate from an underground rhizome and you will keep the variegation.

Jane: I've seen people do this. I've not tried it myself because it always seems much simpler just to divide a plant and make those rhizome divisions - that just seems obvious - but I have seen lots of people on Instagram do this, where they get sections of leaf and root it and I always think, "Well, why are you bothering with that variegated plant?" because then you look at the young plant they've ended up with and the shoots are coming from the green section and you've just got a plain green leaf which presumably isn't... Well, perhaps that's preferable, if you're not into variegation, but, I don't know, I'm not sure why people bother with the leaf cuttings. As you say, you're going to lose the variegation and it's very slow.

Colin: Really, I would say don't bother, with a variegated Sansevieria, trying to propagate from leaves. It's not really the way to do it, in my opinion anyway.

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Jane: Are there any variegated Sansevieria that you do like? I know you're not a great fan, but are there any that you'll make an exception for?

Colin: Bantel's Sensation. I love that, yes, and I've got one or two Trifasciata hahnii variegates and I've got a variegated P**arva, but that's about it. I've got a few hybrids. Now the hybrids are a different matter. I've named one Sansevieria IKEA because a friend bought it from IKEA without a name, ha, so I've called it Sansevieria IKEA! That's one of the thin-leaved forms but I love that because it flowers annually. It really is a good grower. There's another one, very similar, called P**unky, I think. Both of these probably originated from an old hybrid called Fernwood. I don't know what the parents are, but this is a very thin, long-leaved form but they flower very well. We'll come on to flowering a bit later I suppose, but they are great for flowering. I've just got a new hybrid which is P**hillipsiae crossed with Pinguicula. That's going to be quite slow growing, so I'll see how that does. I'm more into the hybrids rather than the variegates, I have to say, in terms of Sansevierias.

Jane: Let's come on to the flowers because you did mention them there. I have not had any of mine flower! I'm very disappointed.Can you tell me how I get mine to flower? I've got a few different species.

Colin: I've grown Sansevierias for over 20 years and I've flowered 30 or 40 different ones. There's no quick fix to getting them to flower. It's choosing the right plants, I would say. I think they will all flower but it can take time. Some need to be very large to flower and some will flower quite small and flower regularly. So my advice, if you want flowers, is choose the right flowering species or cultivars. I've mentioned Punky, I've mentioned IKEA, Fernwood - they all flower for me annually. One of the best ones for flowering is Sansevieria francisii. It's quite small-growing, it has leaves in five tiers, but I have it in flower every year, so that's a good one for flowers. The other side of the coin is Trifasciata, which I've only ever flowered once. You see, quite often, very large plants of Trifasciata and they don't flower very often, so if you want flowers, that is absolutely one not to go for. So it's not a question of any particular trick to getting them to flower. It's growing the right plants that will flower when they're small and will flower annually.

Jane: Is it worth the wait?

Colin: Oh, absolutely! Sansevieria flowers are beautiful. There are two groups of Sansevierias when it comes to flowering. Most of them have tall spikes, some of them have spikes up to a metre tall, the really big ones have large branch spikes which can be one-and-a-half, two metres tall! The other group produce the inflorescence underground, so the flowers emerge at soil level. The only one I flowered in that small group is hallii and that only flowered once but the flowers were magnificent. All Sansevieriasare night-flowering, so the flowers open late afternoon and each flower only lasts one night and they produce the most gorgeous beautiful scents, hyacinth-like I would describe them as, and if you have a flower spike that has, I don't know, 20/30 flowers open in a night, you come down the next morning and the room is full of this absolutely gorgeous scent, but each flower only lasts one night. But if you've got a flower spike with up to 100 buds on it you could have flowers over a course of a week. They have this scent because they attract moths, they're pollinated by moths, so that's why most of them don't have much colour. Some of them have a tinge of pink, there's one brown one, but most of them are white. Moths are attracted by the scent and not by the colour, so that's why they're scented, to attract the pollinators, which are moths.

Jane: I'm glad it's worth the wait. Well, I'm glad you like Bantel's Sensation because I was searching for it so long and mine is a rhizome division, so it has about four leaves right now, but I was panicking because lots of people said, "Oh, it's quite difficult" and I heard from other people who had a piece of rhizome and some leaves and they were struggling, but mine seems to be doing okay.

Colin: It's slow growing, so you just need patience.

Jane: I've never done this but I've always fancied having some kind of mixed Sansevieria trough, or dish, or large pot arrangement, with various different species and hybrids of different heights, shapes and colours. Is that a good idea, or is it better to keep them in individual pots?

Colin: I've only ever done it once. When I was working, there was a planter in a corridor which had nothing in it. It was a metre-and-a-half long trough and it was empty, so I purloined it and I planted three plants in it. I had Zamioculcas, which I know you're very fond of. I had a Dragon Tree, Dracaena draco, and the third plant was a very large plant of Sansevieria fischeri, which is a very attractive cylindrical-leaved Sansevieria and that was a mixed planting that worked very well. I had a very well-drained compost and they thrived. So I have never done any other mixed planting with Sansevierias, but I see no reason why not. If you're putting them in a trough, which is what I did, with no holes in the bottom you just need to be very careful with the watering. So a very free-draining compost, if it was a long large trough like I used, I think I put pebbles in the bottom and top dressed with grit. So, yes, I see no reason why not. Try it and see! There's all sorts of containers available, but if it's a container that doesn't have holes in the bottom, you have to be very, very careful. Go easy on the watering, or most of my Sansevierias are grown in glazed, ceramic or terracotta pots and they've all got holes in the bottom. So if I get a charity shop pot that I rather like that doesn't have holes, I drill holes in the bottom to make sure it's free-draining.

Jane: Do you just match that with a saucer of some kind to catch the drips?

Colin: It depends where the plant's sitting. If it's just on the conservatory floor, it's not so critical, but obviously, if it's on a windowsill... Oh, windowsills have quite often got plastic trays. So the rather attractive glaze pots are sitting on a plastic, rectangular tray to catch the water, yes, so I don't get in trouble with my better half for letting water trickle off on the windowsill.

Jane: You mentioned Dracaena there which brings us on to the slightly controversial issue of the taxonomy of Sansevieriabecause, I don't know who's in charge of this, but some taxonomist somewhere has decided that Sansevieria is actually in the genus Dracaena. I don't think I'm ever going to be able to quite get used to that. When you say Dracaena, I think of things like Dracaena marginata and the Corn Plant, Dracaena fragrans, and they don't seem that similar. Can we just ignore this taxonomic change, or is it something very important that we need to all be switching our language on?

Colin: The background to this is this group of plants we're talking about, nearly 200 species now, if you put the two together, so Dracaena, the Dragon Tree genus, and Sansevieria, as with a lot of plant families' genera, a lot of molecular work has been done comparing gene sequences and, just to simplify the story here, what has been discovered is that Sansevieria is not, from its genes, significantly different from Dracaena and all Sansevierias on that basis have been transferred to Dracaena. So every Sansevieriahas, now, a new name, or the same species name but has now been transferred to Dracaena. That is based on gene sequencing comparisons and this is happening all the time, lots of different plant groups. If you think about it, the 200 species that we end up with in Dracaena are not that divergent, to be honest. There's a wide range of forms, but it's not as vast as some other genera. So let's just quickly compare it to Euphorbia. Euphorbia is a huge genus. It's got 2,000 species and Euphorbia ranges from tiny little geophytic plants to great huge trees and that has expanded recently because a few small genera have been shown to be not distinct on the molecular basis. So the evidence is quite strong that Sansevieria and dracaena are one and the same genus and they all have names in Dracaena. Now, there aren't taxonomic police around here, so if you want to still call them Sansevierias, you can and, to be honest, although as a scientist I accept this new classification, I still call them Sansevierias. I'm a bit of a Jekyll and Hyde character here, so I've accepted splits from Aloe, for instance, so there are several small genera that have been broken away from Aloe, so there's Aloidendron, Aloiampelos,Kumara, so I've readily adopted that but, to be honest, I'm a bit of an old stickler here and I still call my Sansevieria, 'Sansevieria' and, do you know, the rest of the planet can still call them Sansevieria if they so want. The Sansevieria Dracaena police are not going to come away and throw all your plants in the bin because you've got them wrongly named! It's only significant, really, if it comes to shows. So if you had a class that said Dracaena, the show committee or the judge has got to be careful to make sure that they don't NAS i.e 'Not As Scheduled' a Sansevieria that has been put in a Dracaena class, or vice versa. So, in terms of horticulture, that's the only significant place it's important, so I, for one, at least at the moment, am quite happy to call them Sansevierias.

Jane: It does seem to raise emotions. I'm looking on various Sansevieria forums and Facebook groups and there's some very strong opinions out there, but I'm like you, I kind of, well, I'm just going to accept that the taxonomy is correct but, like a lot of plants where the genus has changed over the years, we kind of adopt the old genus name almost as a common name.

Colin: Yes. Well there are big controversies. The Sansevieria world is quite small really. A big controversy raged over Acacia, soAcacia was split up, again on the basis of molecular studies, and that was incredibly controversial. So some of these changes are widely adopted quite quickly and others, there's a lot of inertia and people want to stick with what they're used to. As I say, apart from issues on the show bench, to be honest, it doesn't really matter. As a scientist, I have to say though, I do accept that Sansevieria is now part of Dracaena, but as a horticulturalist I still call them Sansevierias, so there you go! That's me being truly Jekyll and Hyde!

Jane: I've just thought of a question which I forgot to ask you when we were talking about roots. Is there a reason why that rhizome is orange? Does that serve any useful purpose to the plant?

Colin: Pass! I have no idea. That's a very interesting question, Jane: why is a Sansevieria rhizome orange? I'm afraid I haven't a clue. Obviously there must be some pigment in there but I don't know. I have no idea! I'm sorry - you've got me on that one.

Jane: We may never know, but perhaps somebody will have an answer and suggest something.

Colin: To be honest, in science, there are far more questions that don't have answers than questions that do have answers. That's the fascination of science for me, to be honest.

Jane: Yes, indeed, and there's one thing I wanted to ask you which has been a question in my mind for a long time and it concerns the Sansevieria that's on my podcast logo, which I think goes by various common names, including Witches Fingers, Sansevieria cylindrica, and this species and various other cylindrical-leaved species and hybrids seem to cause people a lot of problems because they buy the plants and, oftentimes, they seem to be leaf cuttings that have been rooted and shoved in the pot, sometimes in a different shape than would be natural and people discover they haven't actually got a plant, they've got a selection of leaf cuttings. Then also, when new leaves start to grow, the Sansevieria cylindrical leaves aren't cylindrical when they first come out which really throws people, that they've got a different plant, but I'm presuming that it's just that the leaves start out one shape and mature into that cylinder? Am I right?

Colin: Quite a lot of Sansevierias have two rather different growth forms. So I mentioned earlier Sansevieria fischeri. This is the classic. So fischeri has two distinct growth forms. Its juvenile form is a flat rosette, so these are flattish, thinnish leaves, a flat rosette. As it matures, it produces upright, vertical, cylindrical leaves and that's the adult form, okay? So I've got a clump that has grown from a leaf. So I've taken a cylindrical leaf, I've rooted it and it's produced shoots. This has taken about three years to produce a clump 8cm across. So we've got a cylindrical leaf that's rooted and around it, it's got three or four flat-ish rosettes. So that's standard growth form for quite a lot of Sansevierias and the one you're talking about, cylindrica, isn't quite the same but it's similar. I've got the plant sitting next to me on my desk and I have done the same with that. I've got a leaf cutting that's 25 cm long, it rooted, it's taken about two years and it's got lots of new shoots at the base. The early ones are channelled, they are thin, so what people are seeing is the young immature stage and if you keep it long enough, let it grow, they will all develop the typical cylindrical leaf. If you buy one of these pots from a garden centre that's got half-a-dozen separate leaves, what I would advise you to do is pot them all up separately, so you've got six separate plants and just leave them to grow and eventually you will get clumps which will just have the cylindrical leaf. It will take several years because it's not a fast grower but, in time, it will. So, yes, I do object to garden centres or nurseries doing that because you buy a plant that looks okay but it isn't actually a proper rosette. When you de-pot it, as you say, you've got half-a-dozen separate plants, so they shouldn't be doing that, but they do that because they get a plant that they can sell quicker.

Jane: Yes and it happens with other species as well. You often see it with tropical plants, where they put lots of seedlings in the pot, so you think it's one plant, but it's actually lots of seedlings which then out compete each other and you've got a problem. It's one of those things. I guess it's intriguing and at least, if you know about, it you can solve the problem. I suspect, when you have all those root cuttings in a pot, it's not necessarily going to lead you to ultimate success with that plant.

Colin: Well, it will - you just have to have patience, Jane, because it's not a fast-growing species. Cylindrica is a big-growing plant. It can have leaves a metre-and-a-half long, so what I've got here is a very young plant, but just have patience and you'll get there, eventually.

Jane: I think with Sansevieria that is the key. They are quite slow-growing.

Colin: The hybrids I talked about - IKEA, Punky, Fernwood - they are fast-growing. I got a single cutting and within two years, I've got a 15cm pot full of it and it also sends out above-ground stolons, so some of them are fast-growing, so you've got a range. The slowest growing plant I've got is Sansevieria pfisteri. It has big, thick, chunky leaves. I was given that plant 20 years ago and it is still only in a 12cm pot and goodness knows when I'll get to see that in flower, so some are very fast-growing and some are exceptionally slow-growing and that's the interest, isn't it? If they all did the same thing, wouldn't life be a bit boring?

Jane: Exactly! We haven't talked about feeding. I guess it's the same rule as with other cacti and succulents, that you don't want to over-feed?

Colin: Yes, I feed everything during the Spring, Summer and Autumn once a fortnight. I use Chempak 3 usually. So, yes, my Sansevierias get fed moderately throughout Spring, Summer and early Autumn. I tend to stop feeding them in the winter. So although I keep watering them, I tend not to feed them so, yes, it's just the standard feeding regime for any cacti and succulents. There's nothing special about Sansevierias on that score.

Jane: Marvellous. Well I'm sure that I will be adding further to my Sansevieria collection. They're all on a round coffee table and I'm thinking, "Oh, only two thirds of the coffee table is covered right now. I've got more room to add some more!" So yes, I just keep sneaking them in and hope that my husband doesn't notice!

Colin: I'm going to send you some photographs so people can view some of my images on your website. I think I've got three or four of flowers; I've got about 15 photographs I've selected for you.

Jane: Fantastic! They will be a really great addition to the show notes, so yes, I would encourage listeners to go and check those out and have a look at the plants that we've been talking about. Thank you very much, Colin!

Colin: Okay, you're very welcome! Great to speak with you.

[music]

Jane: Thank you to Dr Colin Walker for joining me to talk about Snake Plants. I've come out into the garden to answer this week's Question of the Week because, well, it's rather hot today and I fancy a sniff of my roses. Wow, yes, this is a beautiful pink rose. Definitely not a houseplant, but it smells absolutely gorgeous and if you look at my Instagram, I've done a reel of some of the roses in my garden, if you want to check them out, but let's turn to the question. I'm just going to plonk myself on the grass here and get into it and it comes from Eliza, who says, "Despite a love for ferns, I suppose, like most humans, I am a fern killer". Well, me too! I've killed a fair few ferns in my time, but Eliza has one fern that has been in her possession "for three years and is still alive and doing reasonably well," Eliza writes. "In fact, it's a monster!" and looking at the pictures, yes, I can see that is true. It's enormous! Not so much of a fern killer after all. Oh, look! Wolfie! Hi, Wolfie! Wolfie has just come up for a cuddle and some sunbathing. Hi Wolfie! In case you're new to the show, Wolfie is my lurcher and show mascot and a very good dog. Right, okay, sorry Eliza - getting distracted here!

So Eliza wants to know what to do about repotting this large fern and she's worried that, basically, it's a bit of a monster and she's not sure where to start and what she can do. Now, I would say, looking at this fern, that it's in the prime of life - it's doing well. I think it's a Pteris genus. I suspect it is Pteris cretica and this is one of the easiest ferns to keep, so that's good news for you, Eliza. I think it's one of the toughest ferns there is. I would say the main thing to say is don't worry too much about repotting it, assuming that you're in the northern hemisphere and it's Spring/early Summer, now is a really good time to tackle this task. With a big plant like this, yes, repotting it may cause a temporary setback but the plant is big enough and strong enough to deal with that shock and will actually benefit from a repot. Eliza's got a self-watering device, a yellow bottle stuck in the top, which is providing water, which is a great idea for ferns, any kind of self-watering really works because it keeps the moisture steady, which is what they love, as you'll remember if you listened to The Plant Rescuer episode, last week - episode 186.

So, how do you know when to repot this plant? Well, you're obviously considering it, which must mean you've seen, perhaps, some kind of signs that the plant is maybe getting too big for its pot? It looks like you've got some roots coming out of the top and, generally, the pot looks rather small in comparison to the size of the plant. I think you're just going to have to go in there and take the pot off, you may need to cut it away with a big plant like that with all those roots pouring out the top, it may be difficult to dislodge, so be prepared to get in there with a pair of really substantial scissors and cut away the pot. Obviously, in an ideal world it's good to avoid cutting the pot so that you can reuse it, assuming it's plastic, you want to get as many uses as possible out of a plastic pot. In sustainability terms, I grow a lot of my plants in plastic pots and they get reused time after time after time. I never buy plastic pots, I either reuse ones I've already got, or I ask around and somebody's always got some to donate.

So I think you can get it out of that pot and assess what's going on. I would take that opportunity to maybe trim some of the more wayward roots. Again, the plant will be able to cope with this. It's got a lot of roots there and it's got a good set of foliage on it, so don't worry too much about taking off some of those roots if you just find you're struggling. So, yes, take it out the pot, have a look, if you've got a situation where you've got a very matted root ball, and it's very hard to see what's going on, again, don't be afraid to get a serrated knife or a pruning saw and just cut across the bottom, it sounds really brutal but sometimes it can be really helpful. If you've got a situation where the roots are all matted and there's no way for those roots to escape out into the new compost you've got a problem on your hands in that they may just start circling around that root ball and may not establish well in the new pot. I would say, assuming that that's not the case, tease out some of those roots so they're going in the right direction into that new compost and put it into a slightly larger pot.

Again, if you're trimming roots, think about balance, so making sure that if you trim some roots you're also trimming a bit of foliage that means the plant has kind of got a balance between the root system and the foliage that it has to support. But I reckon go for it. Ferns like a reasonably moisture-retentive potting mix, so I would do something like a regular houseplant potting mix, peat-free if you possibly can, as I always say on the show, and you could add a bit of vermiculite to that, you could add some fine orchid bark, you could add some activated charcoal. If you are using a self-watering system of some kind, then you may want to make the drainage a bit more sharp, so, rather than vermiculite, you might be putting something like perlite in there. But this fern looks like it's doing really well. Don't panic, have confidence and give it a whirl! Even if it goes wrong, the plant will be fine. I have confidence in this one. I think you're going to be doing well, Eliza, and you have done well, so take comfort.

The other thing to say is, if you don't repot it, what's going to happen? Well, if you decide not to repot, I would just watch out for signs of decline in the plant. If you find the plant is starting to look really miserable then it could be the plant is just not able to get enough resources out of the substrate that it's in and then you really do need to take action. Better to do it now in early summer, when the plant is still in active growth, as opposed to waiting for an emergency in the autumn, when repotting may carry slightly more risks.

I hope that helps, Eliza, and gives you some inspiration for your fern and you say at the end, "Love your podcast but my husband blames you for transforming one of our rooms into a plant room!" Okay, complaints can be filed to the following email address: ontheledgepodcast@gmail.com! Yes, you can point all of your relatives in my direction to moan about the amount of space that your houseplant collection is taking up! If you've got a question for On The Ledge, you can also use the same email address. Be like Eliza and include lots of information and some pictures because that helps me no end. Right, back inside. Wolfie, you can stay and sunbathe.

[music]

Jane: That's all for this week's show. Thanks for joining me this week and I'll see you again in seven days' time. Bye!

[music]

Jane: The music you heard in this episode was Roll Jordan Roll, by The Joy Drops, The Road We Used To Travel When We Were Kids, by Komiku and Namaste, by Jason Shaw. The ad music was Dill Pickles, by the Heftone Banjo Orchestra. All tracks are licensed under Creative Commons. Visit the show notes for details.

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Succulent expert Dr Colin Walker joins me to discuss the wonderful world of snake plants aka Sansevierias, plus I answer a question about repotting a fern.

If you're a Patreon subscriber at the Ledge End or Superfan level, you can listen to Colin talking about Sansevierias and putting me right about succulent fertilisers in An Extra Leaf 71. Scroll down for more information on how to become a patron of the show or give a one-off donation. 

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This week’s guest

Biologist Dr Colin Walker is the outgoing president of the British Cactus and Succulent Society and an expert on succulents, with an interest that stretches back 50 years.

He’s an Honorary Associate at the School of Environment, Earth & Ecosystem Sciences at the Open University, with research interests in cacti and succulents particularly in terms of biodiversity: here's his OU profile.

Some of Jane’s Sansevierias, including (from top left) S. trifasciata var. laurentii, S. Metallica’, S. ‘Bantel’s Sensation’, S. trifasciata ‘Twisted Sister’, S. trifasciata ‘Hahnii’ and S. trifasciata ‘Jade Dwarf’. Also visible are a variegated Hoya kerri and Hoya obovata.

Some of Jane’s Sansevierias, including (from top left) S. trifasciata var. laurentii, S. Metallica’, S. ‘Bantel’s Sensation’, S. trifasciata ‘Twisted Sister’, S. trifasciata ‘Hahnii’ and S. trifasciata ‘Jade Dwarf’. Also visible are a variegated Hoya kerri and Hoya obovata.

Check out these notes as you listen, and scroll down for a gallery of Sansevieria images…

  • Colin has been on the show before! You can hear him talking about Aloes and Agaves in On The Ledge episode 59.

  • If you'd like to find out more about the British Cactus and Succulent Society, visit their website, Facebook page and Instagram account. Why not join and you'll have access to lots of expert advice, cheap seeds through their annual seed scheme and much much more?

  • Sanseveria is a genus of around 80 species, mainly native to Africa, with a few scattered as far east as Myanmar.

  • If you want to check out Hermine Stover’s The Sansevieria Book you can download a digital version.

  • All Sansevierias have tough, fibrous leaves. One of the common names of various Sansevieria species is bowstring hemp, because its fibrous leaves were used for stringing bows.

    Sansevieria care tips

  • Sanevierias love centrally heated rooms - they will die if they are allowed to freeze and are best kept above around 12C.

  • They are often recommended for low light conditions - they will survive in these conditions but won’t really grow. So, if you want your plants to actually grow, give them as much light as you can.

  • Snake plants can be grown in plastic or pottery containers - terracotta pots will dry out more quickly than glazed china or plastic.

  • Colin uses two parts John Innes no 2 to one part grit as his Sansevieria substrate. He recommends repotting straight away if you’ve bought from a non-specialist grower, as the substrate they come in tends to be too water-retentive to work for home growing.

  • Once your plant is in the correct potting mix though, don’t repot until they are bursting out of the pot as some don’t like to have their roots disturbed.

    Sansevieria propagation

  • There are four ways to do this: the first, growing from seed, is not generally your first choice, as seed is hard to come by, and it’s slower than the other methods.

  • You can take your plant out of its pot and pull or cut away part of a rhizome to pot up separately.

  • Some snake plants including S. parva produce overground stolons, so with these, you can cut off one of these, dry off the cut surface for a few days then put it into some substrate.

  • Leaf cuttings also work well: you can chop longer leaves up into short sections and each piece will root when potted into a gritty potting mix - some people also root them in water. This is a slower method, and you’ll find that variegated forms won’t come true to the parent plant - with these, rhizome cuttings are the way to go.

  • The Sanseverias we mention in this episode are: ‘Bantel’s Sensation’, a silvery variegated cultivar that I spent ages trying to add to my collection. ‘Ikea’ flowers annually and is a good grower. ‘Punki’ Colin believes both come from a cultivar called ‘Fernwood’ long leaved form.

  • Snake plants produce beautiful white, scented flowers - they are pollinated by moths so the flowers need to release a hyacinth-like perfume but don’t need to be brightly coloured. if you want flowers, choose the right species: S. trifasciata doesn’t flower very often, whereas ‘Fernwood’ and Colin’s ‘Ikea’ bloom without fail every year. Most have tall spikes up to 1m or 2m tall, others have flowers that emerge at ground level, such as S. halli. Each flower lasts only one night. One of the best species for flowering is S. francisii.

    Sansevieria’s naming controversy

  • Following genetic sequencing of Sansevierias, taxonomists have placed them within the genus Dracaena. This has caused controversy in some parts of the Sansevieria world, and Colin and I agree it’s absolutely fine to keep calling your snake plants Sansevieria if you wish!

Sansevieria gallery

All the images below are credited to Colin Walker.

Eliza’s fern…

QUESTION OF THE WEEK

Eliza wants to know what to do about her huge fern - to pot, or not to repot? the fern in question looks like Pteris cretica, the Cretan brake fern, which makes a great houseplant. People panic about repotting, but this fern grows from rhizomes so it’s pretty tough - wrestling it out of its current pot may well be worth it if it starting to lose condition.

Spring and early summer is a good time to do this, giving the plant plenty of time to continue growing before it slows down in winter. Once you have the rootball out of the pot, tease out the roots, or if you are facing a solid wall of roots, grab a serrated knife and slice away! What you want to avoid is putting the still-solid rootball in a new pot so that the roots just continue to circle around each other. Choose a pot just slightly larger than the old one: you should be able to stick an index finger between the two pots if you nest them together. Fern substrates need to be fairly moisture retentive - I’d add some fine orchid bark and vermiculite to a peat-free houseplant mix.

Want to ask me a question? Email ontheledgepodcast@gmail.com. The more information you can include, the better - pictures of your plant, details of your location and how long you have had the plant are always useful to help solve your issue!
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CREDITS

This week's show featured the tracks Roll Jordan Roll by the Joy Drops, Namaste by Jason Shaw. The ad music was Dill Pickles by the Heftone Banjo Orchestra. All tracks licensed under Creative Commons.

Cacti & succulentsJane PerroneSansevieriaComment