Episode 161: tissue culture explained

Transcript

Episode 161

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Jane: Hello and welcome to On The Ledge podcast! I'm your inimitable, occasionally irritable, but never insipid host, Jane Perrone! Tissue culture - we're hearing about it more and more in the world of houseplants, but what is it? How does it work? And what does it mean for the future of our plants? Chris Reynolds of tissue culture lab, Seedless Labs, in Massachusetts in the US, joins me to answer all my tissue culture questions and yours too, I hope. Plus, we'll be hearing from listener Carl in New Zealand for Meet the Listener and I answer a question about an ivy with a soil that's turned to a brick.

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Jane: Thank you Twanna and Miranda who both became Patreons on this week, your name doesn't have to finish with an A in order to become a member of my Patreon community but it doesn't do any harm! Thanks to EvieMia95, in Australia, for leaving a five-star review for the show and they write, "I hope there will be many more years of On The Ledge." Well, I hope so! I was talking to my husband about retiring the other day and I was saying I never want to retire, I want to keep doing stuff with houseplants until the day I die. I think he might be slightly keener to retire and go and watch cricket around the world, but provided it's in places with lots of interesting plants, I'd be happy to tag along!

A couple of items in the On The Ledge inbox this week I wanted to bring up. Thanks to Christian for getting in touch to tell me that the wonderful podcast '99% Invisible' has just done an episode about peat and its vital role on our planet. I do urge you to go and have a listen and I'll put a link to that in the show notes. If you've heard me bang on about peat in the show but are wondering why, do go and check that out because it's a really nice summary of all the reasons why we shouldn't be using peat in our potting mixes. Thanks also to Derek for picking me up on my mentioning of leaf mould in the potting mix ingredient series. Derek writes, "One thing that I felt would have been good to emphasise in the segment on leaf mould, is that many native insects overwinter in the leaf litter. So for people with trees on their property, it's best not to get too zealous about the fall leaf clean up. Not that I think collecting leaves for potting mix is a bad idea, even a smallish tree will have plenty of leaves to go round but there are ecological benefits to letting at least some leaves stay where they fall." This is very true, Derek. I'm very glad you've brought this up. You're absolutely right. Lots of people love getting those horrible things known as leaf blowers out, and collecting every single leaf from their garden. I ask myself, do you have too much time on your hands for one thing!? In my garden, I tend to leave any leaves that fall in beds because they're just doing their leaf litter job, as you say, Derek, and providing overwintering territory for insects and other creatures such as hedgehogs, who do sometimes come through my garden. I do pick up leaves that fall on the lawn because that can smother the grass and cause problems and usually I just pick them up when I'm mowing. If you've got leaves on your lawn you can always just dump them into the flower beds, you don't have to make a special container for leaf mould unless of course you want to make it for the house in which case you would need to make some kind of leaf mould container or place the leaves into a black plastic sack. In fact, because I don't have many trees bordering my garden, every autumn I tend to pick up leaves that are being offered by other house holders in the area who don't have anywhere to put them, so I usually end up with a few extra bags of leaf mould that way. So even if you don't have a very big garden and do have a lack of leaves, you might be able to get a bag or two, stick it somewhere out of the way for a couple of years and get some leaf mould that way. Thanks very much, Derek, for pointing out the importance of leaf mould and do leave lots of leaves around your garden for wildlife to enjoy if you're lucky enough to have that outside space. A reminder that there's no episode next week, October 30^th^. I'm taking a few days off to spend with my family, so the show will be back again on November 6th.

Thanks to all of you who've supported Legends of the Leaf, on Unbound, my forthcoming house plant book. I'm at 38%. I'm getting there, so that's really exciting! Do check out the show notes if you want to find out how to make a pledge. If you've got any questions about how it works, fire away. I will be happy to help!

I've been on a few podcasts recently. You can hear me on new podcast, 'Gardeners of the Galaxy' with Emma Doughty, which is a wonderful podcast and we talk about plants in space. You're probably all too young to know what I'm referencing there, but anyone who likes The Muppets might know! It was really lovely to speak to Emma, who made a podcast years ago that was one of the very first podcasts I ever listened to and it's great to have her back into podcasting. You can also hear me on 'The Joe Gardener Show' talking about houseplants and I did an Instagram Live with garden designer Diarmuid Gavin on Wednesday this week, if you check out his Instagram you'll find that there' he's @DiarmuidGavin and again that will be linked in the show notes if you want to take a look. I do get about, don't I? Well, especially at the moment, when I'm trying to hawk my book around, but there we go, that's the nature of crowdfunding!

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Jane: There's been a great deal of noise out on social media, and the internet more widely, about tissue culture and houseplants in the last few years, as their popularity has soared. I don't know about you, but sometimes it does my head in, as we would say here in the UK! There seems to be a shroud of secrecy around tissue culture and what it means to our houseplants. So I decided to do my best to remedy that lack of info and today's interviewee is an excellent person to shed some light on this fascinating topic. Chris Reynolds runs Seedless Labs in Massachusetts, a tissue culture lab that specialises in ornamental plants -yes, indeed, all the lovely things we like to grow! Chris was kind enough to sit down and talk to me about the whys and wherefores of tissue culture. Do head over to janeperrone.com to check out the show notes as you listen.

Jane: Chris, I can't tell you how excited I was when your email dropped into my inbox, or maybe it was an Instagram DM introducing yourself, because tissue culture is one of those topics that's been at the back of my mind for quite a while as something to cover on On The Ledge. Us growers don't seem to know that much about it. It's a term that's bandied around but there isn't that much information out there about it. So I'm delighted to have you on the show to demystify this topic. I guess the first, really basic question is, can you explain to us, in terms that I'm going to understand, what tissue culture is and how it differs from the other ways that we might be propagating plants for the houseplant market?

Chris: The basic principles of tissue culture are you're going to take a small sample of the tissue material from the plant, whether that's a section of leaf, a piece of the stem, a single node, and you're putting that into a completely clean environment for that plant to grow. Within that environment you're giving it all of the nutrients that it needs, sugars, micronutrients, macronutrients, to give that plant every possible chance to grow the best it can in that environment. Typical propagation methods of chopping a node and waiting those months for it to eventually grow roots and then start putting out a new shoot, you're kind of taking control of that when it comes to tissue culture. You're immediately telling the plant to start growing those new shoots and ignore any type of rooting activity, so all of its energy is going in, right from the beginning, to create a new shoot and then as many shoots as possible.

Jane: Right, so it's giving you speed that you wouldn't get from other forms of propagation and also presumably in that very sterile environment, you're not going to be subject to any conditions like viruses coming in, things that might come in and affect your crop?

Chris: Correct and that is one of the major benefits of tissue culture. A lot of the industry, that's their main focus now, elimination of disease and pests within their crops when they know they can start a brand new fresh crop with material that has no disease, no pests, they're one step ahead of anything else that could go wrong in that process. So when you're starting that growth with brand new, fresh tissue culture plant material, you know you're not getting any type of disease that's coming from another greenhouse. Everything is coming directly from a completely enclosed secure environment, where none of that stuff can grow directly in your greenhouse, so any of those problems that come up are going to be on the greenhouse side.

Jane: How much plant material do you need, resumably not much, in order to eventually produce quite a lot of plants and where are you getting that material from?

Chris: The plant material can come from any source, any plant that you have sitting on your shelf you could take and do a tissue culture of. You need a very minimal amount of material but it has to be clean material. You want that newest growing tip of a plant, that has the youngest cells inside of it, to be able to multiply that much better. So, if you have a plant that has ten nodes on it, you're probably going to chop those top two nodes from the plants and be able to put those into tissue culture because they're young enough, they have enough of those cells inside them already that they want to continue doing that process where the older parts of the plant, they've kind of lost all of those hormones, so their only focus is the tip of the plant growing and roots growing at the base. You're kind of controlling that beyond there.

Jane: You started your own tissue culture lab in Massachusetts in the US. It's called Seedless Labs. How long have you been going and why did you decide to start this particular business?

Chris: This has been a passion project / hobby for many, many years for me. Lately, with what's been going on in the plant market, this was kind of the push that I needed to go, "Okay, I have these skills, I see all these problems that are happening, why am I working for somebody else to do what they choose? This is my chance to actually have an objective look at the plant market and say what's happening? What can I help? What can I prevent from happening?" You don't really get that if you're working for somebody else. You're typically going at whatever the quickest, easiest plants are going to be. You want mass production of whatever is simple. You don't have any major labs that are looking at the plant market day-to-day, going: "Okay, this is the plant that is being poached right now. Or, this is the one that the hype blew up overnight from". With tissue culture, you're solving these problems on a much shorter basis. You're looking at six months to a year to have something solid in your hands, to be able to send a market where typical chop and prop methods are going to be years to get any amount of plants ready to go to market.

Jane: Are there many tissue culture labs in the US?

Chris: Tissue culture, right from the very beginning, so we're talking all the way back to late 1960s / early 1970s, when this really started to take off and the knowledge started to build around it, it was pretty much instantly sent overseas. Most of the tissue culture labs right now are located in Asia and South America, so they are the main producers right now for most tissue culture in the whole world. You've got a couple of small labs in each country that are doing their own thing, the occasional grower that has a big enough operation to have their own internal tissue culture lab, but beyond that, it's really academics and outside of the US.

Jane: Is that because, putting it in business terms, manufacturing, it's labour-intensive, therefore the labour costs are lower in other countries?

Chris: Yes, that is the biggest cost of tissue culture; labour costs. It's a lot of hands-on. Every part of the process, you need a human being in a sterile environment doing this work. Again, it's become pretty cost-prohibitive, in certain countries, to have that level of manpower for something like that.

Jane: Is that part of your job and what you're trying to do, to be keeping a really close eye on what's going on, in terms of plant trends and identifying things that are up and coming so that you can get ahead of the curve and have those plants available? Obviously, you're a business, but partly altruistically, in terms of 'This is the next big thing! It's going to get poached from its natural environment. Let's try and mass-produce this so that we can make it more available'?

Chris: That is definitely my ultimate goal, is to prevent as much poaching and theft and all of the stuff that has started showing up recently within the plant community that... again, if people knew what tissue culture was capable of, they would probably have the patience for what could come from it. Again, that one lost plant in nature could easily be put into a single test tube and turned into thousands of plants. So you're looking at a single lost plant from nature versus thousands of lost plants from nature that are probably going to die after being removed from their natural environment and stuck inside your living room.

Jane: Is that another key point, then, that plants produced from tissue culture, are they tougher than plants that have been propagated in other ways, or more adaptable?

Chris: I would say more adaptable. You're controlling the environment right from the beginning, you're also able to monitor how those plants are growing. You could have a plant that's towards the edge of the lighting but growing extremely vigorously that you could then subculture beyond that and see if those traits continue. You could very easily have a Begonia that normally is requiring full to partial sun that, for whatever reason, in tissue culture grows fine in low light to partial light and that can then be cultured out to make a plant that is suitable for your needs.

Jane: When you're talking about tissue culture and we hear all these things bandied around on social media about Monstera Thai Constellation and Philodendron Pink Princess and the idea of a sports coming out of tissue culture. Is that something that you're looking out for when you're tissue-culturing a particular plant, for any specimens exhibiting unusual or different desirable characteristics?

Chris: Yes, that is a lot of what people are doing with tissue culture. It's hunting those random sport mutations, whether that be within houseplants or agriculture. There's always that next step that can be taken to find out what that plant is capable of and with tissue culture you're expediting nature. So, in nature, you're going to have that random sport variegation or mutation in, say, one in 100,000 plants. Your average grower is very rarely going to hit the number 100,000 plants in a normal environment. That's very feasible within tissue culture. You're turning individual plants into 30/40/50 plants, giving it a higher likelihood of producing deformities or variegation patterns, or whatever that may be, and that leads back to even a lot of the plants that you see nowadays wouldn't really exist if it wasn't for tissue culture. You've got stuff like that Philodendron Birkin. That was a random sport mutation within tissue culture, so that plant has never seen nature before. The Calathea Dottie, there's so many plants that you see, Thai consteallation, those plants that you just see day-to-day and really don't think about what happened. Even when you hear the term 'sport mutation', even in my mind, leading up to learning tissue culture, I always pictured a gigantic greenhouse, with a thousand of the same plants that somebody is walking around checking the leaves to see if something strange pops out, but nowadays that's all happening inside of a test tube. It's all happening in a lab somewhere, where somebody is looking at a shelf of test tubes and going: "Okay, this one did something different."

Jane: Is there any way for those of us who have plant collections, looking at our plants, to say: "Oh, this plant has X, Y, Z characteristics therefore it's definitely a tissue culture plant" when we get them by the time they reach our homes?

Chris: The biggest telling factor for that, I would say, would be the density of the plant in the pot. A lot of plants are going to grow a single shoot at a time, so when you see things like most Calathea, those are a plant that's pretty slow-growing, that you're going to get one or two shoots every couple of months that pop out, but when you see the plant in store, it's a small forest pot, with dozens of shoots in it, that's not the natural pattern that a plant is going to take. You're going to get those individual shoots at a time. When you see the Calathea, the Philodendron, that has four or five babies coming out of the bottom of it, that's not natural. So, probably, the biggest tell is how dense the plant actually is in that pot and does it grow that way in nature? Beyond that, almost 80%, or more than 80% at this point, of plants sold in any type of big box store are coming from tissue culture.

Jane: Talk me through the whole process from start to finish. What kind of timescale are we talking about? Presumably you're not bringing the plants to market size in your lab? You're sending them on, to be grown on?

Chris: Correct.

Jane: What's the timescale you're working to?

Chris: You're looking at about 90 days to have your baby plants to a point to start multiplying. So about three months to have that initial tissue culture ready to start multiplying to meet whatever that demand is. Roughly six to nine months from your initial culture, you're ready to have those baby plants sent off to a grower somewhere.

Jane: That's pretty quick! That's really quite amazing that's happening in that timescale! One of the things I was interested in, that I noticed on your Instagram, I think, was that you're opening up the opportunity for people to come to you and say, "I've got this plant, can you tissue culture it for me, please?" which seems like an out of this world option. I'm obviously not in the US or in Massachusetts, so I'm not going to be coming to you with a plant, but are you open to people coming to you and saying, "Look, I've got this amazing plant and I want you to tissue culture it". How does that work?

Chris: Most definitely. I'd love to just have the conversation around what people want to do, whether it's me helping them learn how to do it on their side, or it being something that I do. I really just want tissue culture to spread wide. It's, again, one of those secret communities that doesn't need to be secret. It's not secret information; it's science! Science can be replicated by just about anybody. That's my goal, to make people realise that's all it is! It's just science standing between them and something that they don't understand.

Jane: Do you have an understanding of why there is this veil of mystery around tissue culture?

Chris: The biggest thing with tissue culture right now is most of it is funded academically, which means there's always a monetary goal in mind. So, most of the academics are now geared towards crop-specific tissue culture, finding those sport mutations within grapes to find a sweeter grape, or a crop that's resistant to a specific disease, or bananas, for example, there's major problems with bananas in general, but because of tissue culture, we've been able to go back and extract what's needed from the plant to generate a clean plant over and over and over, which is the only thing that's really keeping bananas surviving the way they are right now because they are so prone to disease and other issues that it's a crop that needs to be constantly replenished. That never would be capable of what it has to be without tissue culture.

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Jane: Jackie got in touch to give me a tale of woe about an ivy plant; a Dracaena called Norman! I don't know why that made me chuckle but the name Norman just tickled me somehow! Anyway, so the ivy which, I guess, is the ivy called Ivy - or is that too obvious!? - the ivy, Hedera helix, called Ivy has got a problem with watering, as has Norman. Jackie writes, "I took my ivy out of its plastic container because when I stuck the water meter in it, it seemed like it was remaining drenched down towards the roots but it's completely dry on top and along the sides, which is strange. It gets sufficient light so not sure what's going on? Norman, my large Dracaena, presents with the same issue. Every time I stick the moisture meter in it reveals that it's soaked but it's really not, like the soil is some kind of a brick that's moist in the middle. Anyhow, it's been about two weeks and the ivy has gone on to lose a load of leaves which are turning yellow as well."

Well, this is a good one. I'd love to see what moisture meter you have, Jackie, because a lot of these water meters are being sold now online and I think their reliability is not always great. I've heard lots of reports of people saying that their moisture meters don't work particularly well, or are inaccurate. While moisture meters can be useful, there is nothing better than relying on your own senses to detect when a plant needs watering and that can be as simple as either sticking your finger into the soil right down to the root ball or, if you don't like the sound of that, or indeed if the plant is a spiny one, you can stick a wooden lolly stick or a wooden kebab stick into that root ball and leave it for about half-an-hour to an hour and when you pull it out you'll be able to see whether there's any damp compost sat on it or sat on your finger and that's a really reliable way of knowing whether your plant is moist at root level.

Hedera helix, the English Ivy, it's quite a popular choice for a houseplant but actually it's not entirely suited to conditions living inside unless you happen to live in a house that has unheated areas where the temperature doesn't stay at that standard 19C/66F because ivies really are garden plants and they will come indoors and be okay in the summer and when the heating comes on, assuming you have fairly reliable heating, oftentimes these plants will start to struggle. The yellowing and falling leaves, Jackie - I suspect that the plant is having a bit of protest about something or other. It may well be that it is soaked around the roots and that's why it's losing those leaves. In order to back up what the moisture meter is saying, you really do need to get your finger in there. I'd want to know what's happening around root level, so I'd be unpotting that ivy and having a good look at the root ball. It may just be that the soil has become compacted and dried out and the plant is pot-bound or, as we also call it, rootbound, so there's just a mass of roots which is making the soil go very, very heavy without those essential air pockets that plants need and therefore the moisture meter is not reflecting what's going on around the soil either, because of inaccuracy. It may well be that the moisture meter is completely right, the top of the surface is completely dried out but round by the roots of the plant, it's a quagmire. There's no real way of knowing other than getting down and dirty and getting into that pot and seeing what's going on. The ivy definitely won't like it, indeed, Norman the Dracaena won't like it either, to have roots that are sat in water, stagnant, sitting there for weeks at a time.

If an ivy is in too warm a room, especially in winter time, it is absolute manna for our least favourite pest, the red spider mite, so it's really worth paying attention to this plant's needs if you do want to have one, and if that doesn't sound right for you then do look at other houseplants which are ivy-ish but more suited to indoor growing, such as Plectranthus verticillatus, the Swedish Ivy, which is a great choice of plant and will cope with that hot, dry air, no problem. I think, oftentimes, we don't want to do that bit of investigation because it's a bit of a hassle, isn't it? Taking the plant out of the pot, digging around, you don't know what you're going to find and suddenly a two-minute job turns into a half-hour job, as you struggle to repot the plant, or whatever, but it really is worth looking if you want to identify what's going wrong with this ivy. The Dracaena, you didn't send a photo of that, Jackie, but I imagine it's the same story. It may be that the compost at the bottom isn't well-enough drained and that water is sitting around, or your moisture meter is up the swanny, so either fall back on the old finger or get yourself a new one.

Like most gadgets, it's worth spending a little bit more money on one of these because the really cheapo-cheapo ones that you see on that big website beginning with an A, oftentimes they really are so unreliable as to be not worth it. If you have any thoughts about Norman and his friend Ivy, then do get in touch, and if you've got a question for On The Ledge - ontheledgepodcast@gmail.com is the best way to get in touch.

Now it's back to my chat with Chris and I wanted to find out more about the ins and outs of tissue culture and how it's impacting on the houseplant industry.

Jane: Do you think the huge boom in houseplants, and presumably the amount of money being spent on houseplants, is going to mean that houseplants do take more of a central role with things like tissue culture?

Chris: Yes. I hope to see that happen because it does seem to be an industry that is veering very quickly to one specific area, that is agriculture where everything, again, works exactly the same when it comes to ornamentals. There's nothing different between how I would duplicate a tobacco plant versus how I'm going to duplicate a Philodendron. It really does come down to where those needs are and who is willing to fill that space.

Jane: If houseplant tissue culture had the same levels of investment and attention as food crops, where would we be? Who knows?

Chris: The capabilities are there, it really is just where that funding is going to, or who is showing that interest of where their next steps could be. Again, houseplants are no different than any other plant out there, so I see this going in that direction now that there is the boom that there is with houseplants. It's something that other people are talking about and thinking about and up to this point most of the studies that have been done on ornamental plants have been for medicinal value. So most of the studies that have come out, even for tissue culture, have been with the prospect of finding a medicinal value within that plant.

Jane: I'm wondering if things like finding particular sports that have particularly good - I always think houseplants cleaning the air is an overrated thing - but you could imagine that some work on tissue culture could bring about plants that are super-good at absorbing particular VOCs from the air, or grew in a particular way that made them very suitable for a particular kind of environment, like a particular kind of green wall. I think there's many applications that you could make and with us understanding so much more now about the benefits of plants and biophilia then, perhaps, this will be something that will be further investigated. It's fascinating to think about what the future holds. One other question I had for you, going back to the tissue culture such as Thai constellation and Philodendron Pink Princess, if they're a result of tissue culture, why do they still cost so much money in the sense of the demand and supply seems to mean that they're not that common still, or they're not in every single big box store, in a way that Philodendron birkinis. Is there a particular reason for that? Is it because they're more unstable and therefore harder to mass produce?

Chris: A couple of different things. The biggest thing is the costs associated now with getting into some of these plants, where most of these labs are overseas, in areas that don't necessarily have the access that we have to certain plants, that don't have the money to make the investment to take a plant that's unknown how to tissue culture and do all of the testing that's needed to figure that out. If you're going blind, as a lab, into doing the Thai constellation, I can tell you there's no solid information out there for others to learn how to do a Monstera. So you're kind of running those tests on your own from the ground up which - I'll tell you my testing for Monstera has started with 50 nodes for me to narrow down what the best concentration of hormones is, to figure out what the best lighting is, whether it should be kept in the dark at the beginning, or left in the light from the start. There is a lot of variables that go into it at the beginning and when you're talking about a plant like Thai Constellation, or a Pink Princess, where you could ping upwards of $100 a node now, it could be definitely cost-prohibitive for some people to even consider working on that plant. Something like the Thai constellation, that again was a sport that was discovered within tissue culture which led to its ease of being continually tissue cultured. Pink Princess, that isn't difficult and I don't know why it's as expensive as it is - I'll be completely honest with that one.

Jane: It's a mystery, isn't it? I guess I'm just hoping that the price of that plant does come down. I would love to have one, I wouldn't say it's a plant that I'm going to die to get but perhaps it will be, perhaps it'll be like birkin and in a year-and-a-half it will be much more common and there's somebody somewhere in the world who's producing vast ranks of this plant and they're going to flood the market and the price would come right down.

Chris: That's my hope, that's truly what I want to do with some of these houseplants. When I look at something like the Pink Princess, again, it does work no different than the birkin. I may have a slightly higher failure rate of plants but, again, when you're producing 40, 50, 100 plants, that loss is minimal and it's not any more difficult than any other Philodendron. The work that goes into replicating a birkin is the same work that goes into a Pink Princess. So, I think, right now, we're at a weird point with that plant. So back around 2008 was when that first went into tissue culture and started getting mass produced from a couple of labs. For whatever reason, it kind of faded between then and now, and a lot of the labs which were producing it stopped. So, if you go back almost twelve years now, most of those Pink Princesses that have come out since then are tissue culture. Whether your plant is directly from tissue culture, or the mother plant was from tissue culture, chances are you have a tissue culture Pink Princess.

Jane: We'll have to wait and see on that one. Thinking ahead also to other plants that are coming up on the rails in terms of popularity, I'm wondering if there are particular plants that just don't respond well to tissue culture? I'm thinking in terms of Hoyas as, unfortunately I would say, as somebody who rather likes Hoyas and rather likes collecting them and doesn't want to see the price go sky high, they seem to be coming up as increasingly in demand plants. I'm wondering if they are good candidates for tissue culture because I've never heard... I know they're semi-succulent, but I've never heard much talk about succulents and cacti in terms of tissue culture?

Chris: They're definitely an ideal candidate, especially being, again, cacti and succulents. When they're slow growers, you can control that environment and make things happen a lot quicker than they would on their natural progression. I actually started looking into Hoyas recently because there really isn't a huge tissue culture market right now for Hoyasbut I do see that happening. It's the Hoya Kerrii that's the only one that I'm aware of that is being mass-produced within tissue culture, but that also means that that door is now open for adapting what worked with that plant to other Hoyas, to see if that still works and chances are it's going to be pretty close and the same possibilities will be there.

Jane: Are there any advantages to the non-tissue cultured approach? Are there any reasons why certain plants, or will there always be a section of plants that aren't tissue-cultured?

Chris: I really think that is the biggest limitation, is having the necessary facilities and knowledge to do it, because it's always going to be, in my opinion, a better way of doing things. You're doing things on your own timeline. For example, right now, we're going into winter and I don't need to run a full greenhouse. I have three metal racks filled with containers of tiny plants that I can continue multiplying throughout the entire winter without any worries and then as soon as the season hits, I've got all of these plants ready for me. It's definitely the approach that I see being best. There's always going to be some plants that may be quicker and easier. I don't see somebody spending the time to tissue culture something very basic, something that grows very quickly, but there is still reason to do it and there's a lot of viruses that are transferred between plants and that's the safest way to guarantee that clean stock that you know you're not going to bring in a tray of plugs from XYZ grower and end up wiping out half of your greenhouse because of that.

Jane: When you're getting that original material that you're using for tissue culture. As I understand it, it's sterilised, isn't it? There's no chance of any viruses getting through the tissue culture process because of the way the material is treated? Without getting too technical, am I right about that? You do some kind of process to remove any potential viruses or bacteria from the material?

Chris: That's correct. Your normal tissue culture is going to deal with any pests and pathogens that are in and on the plant. When it comes to viruses, that's a little bit trickier. With that, you have to use the apical meristem of the plant, so the very, very top shoot that's coming out, dig down to where it's got its newest freshest bud that's starting there, and then tissue culture - that typically doesn't contain the viruses and more damaging things that were typically carried in that plant. Again, any of that stuff is possible to do and that is what some of the other industries are relying on tissue culture for specifically, so something like the cannabis industry, they have plants that are on a definite time frame that get these viruses, get these pests, that are eventually going to die or lose their vigour and tissue culture really is the only way to get that plant back to a strong new plant.

Jane: Is there anything you're doing, any particular plants you're working on right now, that you're able to tell me about, particularly exciting, or anything you're seeing elsewhere in the tissue culture world, not even necessarily being done by yourself, that is worth noting?

Chris: Yes, most definitely. I'm an Epipremnum nerd. That's what I like to work with. I'm actually chasing sport variegations right now in a couple of different plants, Cebu Blue being one of those. That's my side, passion project right now, is hoping that I can get just something weird with that plant to pop up in tissue culture. Beyond that, I'm really trying to work with some of the less common plants. I don't want to say rare, but the ones that aren't at big box stores right now that could be. So whether that be Epipremnum Shangri La, that's such an odd plant that is forgotten when anybody talks about that family and it's such a weird, beautiful plant that grows so slow compared to all of the other ones. So that's exciting for me to get this weird plant, or at least plant that I've found very weird since I started working with it, out to people. For me, the slowest-growing plants are always going to be the best candidates for tissue culture. It's going to be the best way to get something that grows slow, or doesn't typically survive. It's a lot of fun, honestly, just to watch all of these plants sit inside of a test tube and wake up every day and see what they're doing, or what they're starting to do! Right now, we've seen a huge influx in the United States, not really sure what lab that they're coming from, but the Alocasias, the dual Alocasias, the Dragon Scale, the Silver Dragon, those have been coming out en masse from a tissue culture lab widely hitting the market in the United States, which has made a good dent in the price of a plant that was once $200 and is down to probably around $50 in at least the garden centres around me here. Even that is a huge step in the right direction to getting these plants into people's hands.

Jane: Going back to the Cebu Blue, there's so much confusion on social media about "Is this a Cebu Blue? Have I bought something, or is it some other plant?" Can you shed any light on that because there does seem to be so much confusion about it. People think they're being sold a Cebu Blue and somebody else comes in and goes, "No, that's not a Cebu Blue" and I'm, like, "I don't know!". People ask me this question and I really don't know, but I don't know if you've got any insight into why that particular one? Is it the old sore with Aroids, that the juvenile foliage is very different and also there's lots of variation within the species, as there is with other Aroids?

Chris: The biggest factor is that people, especially the stuff that's coming out of tissue culture, those juvenile leaves are not going to be representative of what that plant looks like. Even the leaves that come out in tissue culture may not look like the plant normally would, just because of the environment that it's been kept in. It's in 100% humidity, when the plant is not normally dealing with that. Because of that environment, it doesn't form its wax coat on its leaves yet. Things do grow funky in tissue culture and it's not until you get it into its normal environment, and let it start growing, that you see what that plant is actually going to look like. Cebu Blue, again, it's no different than the green version, other than having the slight blueish tint on the leaves, that's really the only difference, to me, between Cebu Blue and just a regular Epipremnum pinnatum that has the greener leaves on it. When you see them side by side, it's pretty obvious which plant is which, but I can definitely see somebody having only one or the other and not understanding which one it is. I think, going back, I remember at some point there was somebody selling just the regular green version as Cebu Blue and that tends to be what sours the market quickest. It really just takes that one person of doing something wrong to tarnish that plant across the market for everybody.

Jane: Epipremnum Shangri La, I have to disagree with you here! I find this plant quite disturbing because I'm always looking at that distorted growth and going, "Oh my gosh; pest infestation!". If I had one, not that I do, but I'd be constantly panicking that it had thrips, or something, because of all that weirdness and it makes my eyes start twitching when I look at it! I'm, like, "Oh, no!" but I could understand that everyone's got their own things that they find appealing, so don't be led by me on that, but it is an interesting plant because it is very twisted, isn't it? It does look other-worldly.

Chris: It is. It doesn't function like other plants do. It has those weird, crinkled leaves and its growth patterns are very different than its parent plant, which I'm hoping to narrow down. There's little information about what the parent plant is of a lot of plants and that's something that can be researched within tissue culture. So, having a plant like that, and being able to return it back to its juvenile state, is hopefully going to narrow down where that plant actually came from. That's one of my goals as well, to be able to definitively say where some of these plants actually came from. There is debate on who the parent plant was, who the breeder was, for so many plants, and tissue culture can kind of demystify a lot of that. Another one that I'm really excited to start working on very soon is the Rhaphidophora tetrasperma. That's had all the controversy around tissue culture and is really the plant that brought that term into most people's vocabulary. I'm still not 100% on why that plant looks the way it does.

Jane: I've missed out on this controversy. What was the controversy about that plant?

Chris: There's still debate whether the plants that are being sold across the world as tetrasperma are Rhaphidophora tetrasperma, or Rhaphidophora pertusa, I think is the name?

Jane: This is ringing a bell now, yes. I have heard about that, yes.

Chris: In my mind, the only way I can solve this problem is by getting a specimen that is definitely not from tissue culture of a tetrasperma and putting it into tissue culture myself and seeing what the plant looks like when it comes out. Again, being on the tissue culture side and knowing plants look different, it can take a little while. I ran out and got one myself right away when they hit market and I was on the team saying, "Nope, this is definitely what the plant is. Eventually the leaves are going to look normal" and now we're going on nine months to a year and I think my plant is probably close to about five feet tall now and is still putting out its juvenile leaves, or the leaves that it's permanently with now, which are slightly different than what you would see in a wild tetrasperma.

Jane: The plot thickens! Keep me posted on that. That sounds fascinating. One other thing I saw on your Instagram that really got my attention, and it's something I've been wanting to dig into, is your discussion about a technique that you can use at home for rapid propagation which is not tissue culture, but which is inspired by the same kind of logic, which is the use of Cytokinin paste, which I think, is that term interchangeable with the term 'Keiki paste'?

Chris: For the most part, yes. It's really going to be the same thing. Keiki is just a term typically used within the orchid community. It hasn't really bled out beyond that.

Jane: I had this listener question and it occurred to me, after looking at your Insta and things, that this actually might be quite relevant for this listener who'd got in touch with me. Jacob has got an Alocasia Odora Variegata and this plant is basically putting out all white leaves and they're concerned that's not good because the one green, variegated leaf that's left is not able to support the rest of the plant. He's got it under a growlight, he's being all super-careful with it, but I'm just wondering whether that Cytokinin paste could be an answer for him, in terms of applying that to a node where he can see there's still plenty of green in order to promote new growth that's more sustainable?

Chris: Yes, Keiki paste is the same hormones that are going into tissue culture. Right now the only difference I see is the concentration. Everything that's been made for Keiki paste up to this point has specifically been geared towards orchids which, again, will work with a lot of other plants. We have tested just the regular orchid Keiki paste on dozens of plants and seen at least some results from all of them. It tells you that capability is there. The only thing that we need to tweak at this point is going to be the concentrations of it. What goes into making that node grow on a Hoya is going to be different than what makes it grow out on an Alocasia, or a Philodendron, or a Monstera. My goal now is to go back to what's happening in tissue culture,what concentrations of these hormones it's taking to make that happen inside of a test tube and adapt that to a topical paste that can be used.

Jane: Is it worth people who are interested in this kind of stuff getting hold of some of this paste - I have seen it available in the UK. I'm sure it's available in the US as well - and just doing a bit of experimentation with some of their plants, applying it to a node and seeing what happens?

Chris: Most definitely. Again, no harm, no foul, iff it's a plant that you're not concerned about. I wouldn't say grab your Monstera albo and start slapping this paste all over it, for reasons. If you have a plant, there's no reason not to. I think I posted the picture on my Instagram recently of a Peperomia. Again, half the leaves had fallen off, my wife made a comment about it, threw the paste on there and sure enough all of those leaf sites we have entirely new shoots coming out. That was just with regular Keiki paste. Now I'm diving into it a little deeper, to tweak that concentration and see what works best. Yes, anybody should go out and get Keiki paste and try it. That can be just as easy of a first step in the concept of tissue culture as using rooting powder because that's also the same chemical that goes into tissue culture when we're trying to get the plant to grow roots. These are all happening externally now.

Jane: So it's just a question of identifying those growth points on the plant and applying the paste and observing, I guess?

Chris: Observing, yes. Playing a waiting game.

Jane: That is the game we're all playing with all kinds of different experiments we try. That sounds like a really interesting thing to try. Chris this has been so fascinating and I've kept you for a good amount of time here. Are there any other things you wanted to drop into this main interview that we haven't covered already, about tissue culture, because it's so fascinating, but I don't want to miss anything if there's anything important that we haven't covered?

Chris: I would say look towards the future of it, where we're constantly progressing with tissue culture. I want everybody to feel like they can learn something new. You don't need to be a scientist that's spent eight years inside of a lab to understand what's actually happening with this. You can take it as simply or as complicated as you want. The future is definitely going to be a lot more round the actual gene control of the plants. That is what the future holds; the ability to go in and edit those genetic markers inside of a plant, to make something happen. For example, taking something like a tetrasperma that's in tissue culture and being able to edit those cells to make it variegated. That's going to be the future. We're going to see that in a very, very short amount of time, I think. Another thing I just posted about recently, was a team of scientists just discovered the ability to add bioluminescence into tobacco plants. So they take that gene from fungi and edit it into the genes of a tobacco plant. So now you have a tobacco plant that's generating most of its own light, so you can see what that could do within houseplants. If you have a plant that's generating some of its own light, you've now taken away that obstacle of lighting in your house. You've got a plant that can be doing that on its own. There's a lot of crazy stuff that can happen and I think the more people that get involved, the more people that get their hands on it, the more questions get asked and the quicker this can happen. Where it's so secretive, I don't want it to be that way any more. I want regular people to have that interest and go, "Well, what does this mean?" and take that next step of learning.

Jane: Well thanks so much for joining me today, Chris. I've learned loads and I'm sure my listeners have the same. I'll put in the show notes all the details about how to get in touch with you at Seedless Labs because I'm sure there'll be a few listeners beating a path to your door for a chat as a result of this because it's fascinating stuff, so thanks very much, Chris.

Chris: Thank you!

Jane: Chris was too modest to say so, but Seedless Labs is also offering tissue culture classes, so do pop over to my show notes or have a look at their Instagram @seedlesslabs to find out more and check out what they're doing.

Jane: Now it's time for Meet the Listener. Today we're hearing from Carl in New Zealand and I'm resisting the temptation here to do a very poor New Zealand accent, which you should all be very grateful for!

Carl: Hello, my name is Carl. I'm a 33-year-old home gardener and houseplant collector here in Auckland, New Zealand. I'm only a relatively new listener to On The Ledge podcast, which I discovered during the lockdown after listening to Plant Daddy podcast. I have around 300 house plants which I dote over and I always seem to find myself collecting more. Auckland is a great place for keeping houseplants because of our very temperate environment and probably one of the reasons why so many houseplants have become weeds in this city.

Jane: Question one. You've been selected to travel to Mars as part of the first human colony on the Red Planet. There's only room for one houseplant from your collection on board. Which plant do you choose?

Carl: If I was on my way to Mars and had to take only one of my houseplants, I'd be boarding with my Zamioculcas zamiifolia. I've had it for quite some time and it's quite a large specimen. I really do feel like it's got the tenacity and hardiness to survive that long journey and wouldn't mind the potential lack of water and light that it might experience on Mars.

Jane: Question two. What is your favourite episode of On The Ledge?

Carl: I'd have to say my favourite episode is 145 with Tyler Thrasher. You both gave some fantastic advice about not being bound to normative careers. I loved hearing Tyler's perspective on plant science and art - all three things I'm very passionate about. Hearing Tyler talk about the Black Lives Matter movement really hit home to me how we still have a lot to do to work for equal rights for all people of colour and support those cultures broken down by colonialism, New Zealand still being one of those countries.

Jane: Question three. Which Latin name do you say to impress people?

Carl: The Latin name I say to impress people is most definitely Amorphophallus paeoniifolius. People always look at you a little funny when they click as to what Amorphophallus actually means! I always feel a sense of achievement when I manage to say paeoniifolius correctly.

Jane: Question four. Crassulacean acid metabolism or guttation?

Carl: While I am fascinated by crassulacean acid metabolism and want to try the litmus test on my own Crassula one day, I do prefer guttation. I have a Rhaphidophora tetrasperma next to my bed and love seeing the little droplets at the tip of the leaves. I feel like it makes the plant appear fresh and clean but also because it's telling me I've probably watered it a little too much.

Jane: Question five. Would you rather spend £200 on a variegated Monstera, or £200 on 20 interesting cacti?

Carl: One day I do want to own a variegated Monstera, but in New Zealand they're worth a lot more than €200. €200 would probably only buy me an unrooted cutting. I'd be buying the 20 interesting cacti. I don't have many cacti in my collection and I would love to expand it with some larger varieties.

[music]

Jane: Thank you Carl, what an interesting choice, the ZZ plant, or the "Zed Zed" plant if you're being particularly English! I agree with you - that would make a great plant to take into space because it is so tough but I don't know if I'd be a bit bored? I hate to be a downer on Zamioculcas zamiifolia but then again it would be better to have a boring plant that's alive at the end of the journey, than an interesting plant that's dead! I totally understand your rationale, Carl! If you'd like to hear your own voice on this show, then do drop a line: ontheledgepodcast@gmail.com and my assistant, Kelly, will drop you a line about how to take part. We've had quite a lot of interest recently, so there's a few recordings stacking up, so do listen out! You could be telling me whether you like guttation or CAM in a podcast near you soon.

That's all for this week's show! I shall be back in two weeks because remember there's no episode on October 30^th^. I shall be gallivanting, as much as one can do during a pandemic, with my children, and I will be back on November 6th with a fresh episode. If you need your On The Ledge fix while I'm off, then do go and check out the thematic page of all On The Ledge episodes, which also includes interviews I've done with other podcasts and, of course, if you're a Patreon subscriber, a Ledge-End or a Super Fan, you can tap into all the extra episodes of An Extra Leaf. Thanks to my guest Chris Reynolds and to Seedless Labs. I hope you enjoyed this extra-long episode. Have a splendiferous week and if you can't have a splendiferous week, then have a safe week. Perrone out!

[music]

Jane: The music you heard in this episode was Roll Jordan Roll by The Joy Drops, An Instrument the Boy Called Happy Day, Gokarna by Samuel Corwin and Whistle by Benjamin Banger. All tracks are licensed under Creative Commons. Visit janeperrone.com for details.

Subscribe to On The Ledge via Spotify, Apple Podcasts, Player FM, Stitcher, Overcast, RadioPublic and YouTube.

I learn about the science of tissue culture and what it means for the houseplant industry with the help of Chris Reynolds, founder of tissue culture lab Seedless Labs. Plus I answer a question about an ivy and a Dracaena called Norman, and we hear from listener Karl.

This week’s guest

Chris Reynolds is the founder of Seedless Labs, a tissue culture lab in Massachusetts in the US that specialises in houseplants. @seedlesslabs on Instagram or check their website for contact details.

Some notes to check as you listen to my intro:

Some notes to check as you listen to my interview with Chris Reynolds:

  • Tissue culture involves growing plants from a small piece of plant tissue in a nutrient solution that takes place in a sterile environment. Each new plant is a clone of the parent plant. There’s an interesting piece on the history of tissue culture at the start of this academic paper.

  • The tissue culture process takes six months to a year, which is far quicker than traditional ‘chop and prop’ methods of multiplying plant stocks.

  • Calathea roseopicta ‘Dottie’ (here’s the patent for that cultivar), Monstera deliciosa ‘Thai Constellation’ and Philodendron ‘Birkin’ (a sport of Philodendron ‘Rojo Congo’) are three examples of plants that emerged as ‘sports’ discovered during tissue culture.

  • Most tissue culture labs are situated in South America and southeast Asia: the majority focus on food crops, not ornamentals including houseplants.

  • Chris calls himself an ‘Epipremnum nerd’ so he loves working on E. pinnatum ‘Cebu Blue’ and slow-growing E. ‘Shangri La’.

  • Raphidophora tetrasperma was the subject of a lot of debate about whether the plants being sold around the world were actually as tetrasperma are actually R. pertusa. Chris hopes that tissue culture will be able to provide a definitive answer to this question.

  • If you want to play around with some of the principles of tissue culture, Chris says a good place to start is with some keiki paste which contains the hormone cytokinin, which is used in tissue culture. Apply the paste to a node that you’d like to see some new growth from, and observe what happens. Here’s a useful page on using the paste on orchids (where the name originated from). Planted in Seattle’s video on using the paste on aroids is also worth watching.



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Question of the week

Jackie’s ivy (pictired left) and her Dracaena Norman are both causing some confusion: the moisture meter is telling Jackie the plants’ soil is wet at the roots but the soil at the surface is bone dry. The ivy has some yellowing foliage and is dropping some leaves.

I suggest the gadget may not be giving an accurate reading, and it’s important to test the moisture levels in other ways: sticking your finger into the potting mix to rootball level and seeing if your finger comes out clean and dry or wet and soil-covered. You can also stick a wooden lolly or kebab stick in the rootball for 30-60 minutes if you don’t want to use your finger.

Hedera helix aka English ivy can be hard to keep alive indoors: an alternative is Swedish ivy, Plectranthus verticillatus, which tends to be happier in centrally heated rooms.

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!

HOW TO SUPPORT ON THE LEDGE

Contributions from On The Ledge listeners help to pay for all the things that have made the show possible over the last few years: equipment, travel expenses, editing, admin support and transcription.

Want to make a one-off donation? You can do that through my ko-fi.com page, or via Paypal.

Want to make a regular donation? Join the On The Ledge community on Patreon! Whether you can only spare a dollar or a pound, or want to make a bigger commitment, there’s something for you: see all the tiers and sign up for Patreon here.

  • The Crazy Plant Person tier just gives you a warm fuzzy feeling of supporting the show you love.

  • The Ledge End tier gives you access to two extra episodes a month, known as An Extra Leaf, as well as ad-free versions of the main podcast on weeks where there’s a paid advertising spot, and access to occasional patron-only Zoom sessions.

  • My Superfan tier earns you a personal greeting from me in the mail including a limited edition postcard, as well as ad-free episodes.

If you like the idea of supporting On The Ledge on a regular basis but don't know what Patreon's all about, check out the FAQ here: if you still have questions, leave a comment or email me - ontheledgepodcast@gmail.com. If you're already supporting others via Patreon, just click here to set up your rewards!

If you prefer to support the show in other ways, please do go and rate and review On The Ledge on Apple PodcastsStitcher or wherever you listen. It's lovely to read your kind comments, and it really helps new listeners to find the show. You can also tweet or post about the show on social media - use #OnTheLedgePodcast so I’ll pick up on it!

CREDITS

This week's show featured the tracks Roll Jordan Roll by the Joy Drops, An Instrument the Boy Called Happy Day, Gokarna by Samuel Corwin, Chiefs by Jahzzar and Whistle by BenJamin Banger (@benjaminbanger on Insta; website benjaminbanger.com).

Logo design by Jacqueline Colley.