Episode 178: leaf botany part five - dormancy
Beeches can hold onto their dead leaves: a phenomenon known as marcescence.
Transcript
Episode 178
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Jane: Is your plant stone dead or is it merely resting? We find out in today's episode of On The Ledge. I'm joined by Matt Candeias of the In Defense of Plants podcast, and now book, to find out all about dormancy this week and I share some of your tales of woe about the plants that didn't make it.
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Jane: When I'm thinking about plants of mine that aren't doing very well, perhaps they've got one dead leaf or sometimes the whole thing has just turned to dust, I often think of Monty Python's parrot sketch because I'm wondering to myself is it actually dead, or is it just resting!? The botany of dormancy is something that I've had a lot of questions about from listeners over the years, so it felt like time to turn this latest leaf botany episode into an examination of what's really going on when our plants go dormant. What is the leaf botany series? Well, it's a very occasional episode covering different aspects of how our plants grow, we've covered pigments, we've covered shape and, this week, Matt Candeias of the In Defense of Plants podcast is here to talk to us about when our plants decide to take a break.
Matt: Hi Jane, I'm Matt Candeias, I'm a community ecologist by training with a specific focus on plants. I'm also the host of the In Defense of Plants podcast and blog and I've recently dived into the world of authorship. I wrote a book called In Defense of Plants, an exploration into the wonder of plants, and it is an absolute honour to be back on the podcast with you today.
Jane: The topic that I want to get into with you today is dormancy because I've had a lot of listener questions about what dormancy is, what it means, what it does to the plant and I'd love to have your professional viewpoint on this or, not viewpoint, professional chapter and verse because I really don't know the answer! Is dormancy one of those terms which is strictly defined in botany, or is it one of those terms that has a few different meanings?
Matt: Yes and no. I think it has a stronger definition than a lot of terms can have in botany, but, largely speaking, it's just a cessation or an arresting of plant growth for a period of time that can be triggered by a variety of factors. The key factor is that it's a stopping of the meristem growth and that can mean a lot of different meristem tissues but as long as they're not growing, technically, that's dormancy.
Jane: So just for those of us who've not heard that term before, the meristem growth, that's the growing points of the plant presumably? The points where it can develop new tissue?
Matt: Right. Tips of branches, the sets of tissues just directly under the bark for trees, so it's undifferentiated cells that can then begin to expand, grow, differentiate into new branches, leaves, that sort of thing.
Jane: This has become a bit of a hot issue, I think partially because of one of those lovely internet things that happens, where suddenly you start seeing something over and over again and wonder where it's come from and you think, "Oh yes, it's somebody on Instagram talking about this!". There seems to have been a bit of a thing where people are talking about "half-dead leaves" on plants and whether they are a liability for the plant or whether the plant needs them until the point where they're completely dead. I'm not explaining this very well! The question actually came from Taylor who says, "While trimming old leaves off plants I wonder at what point old leaves become a liability? I err on the cautious side and assume they're at least photosynthesizing, even if half-brown and crispy, but I also realise that leaves are shuttling energy into old leaves to keep them going. Long story, short question: when do you choose to remove the old foliage so it's not a drain on the plant?" Now I know this isn't directly dormancy, but it's kind of connected in that sometimes plants obviously do lose their leaves during a dormant period and this idea that they're draining the plant goes against my botanical instincts. Can you shed any light, Matt?
Matt: It is completely false. They're not taking a drain on any of aspect of the plant. I think what Taylor's referring to here is actually senescence, so the drawback of older leaves, usually down farther below the active growing tip, and it does look alarming at first. That's always the big question, is what's going on here? Then I always have to ask are these leaves at the top of the plant, at the bottom near the base, or out towards the tips, depending on the growth habit, but this is senescence which can pre-empt dormancy for a lot of species, but it's also a regular part of active growth as well. Plants will pretty much shut down any organ that's not giving back to net photosynthetic gain, so in the context of a leaf, if it's older, damaged, maybe just not getting as much light as the other leaves, they'll start to shut that leaf down and excise it from the growth because if it's not giving back it's actually more of a drain to have it on there. So what you're actually seeing is a good thing, it's not showing that the leaves are trying to keep old leaves going they're actually taking nutrients out of them, reclaiming some of what had been invested into that leaf, which is why they start to turn yellow and different colours. It's like fall [autumn] colouration, you're seeing a drawback of compounds, like chlorophyll which is high in nitrogen, and then that's revealing other compounds in the leaf that are different colours, like yellows and reds. So this idea that it's a liability is false. I think the only liability you could possibly point to is if they fall on the soil and start to rot you could get fungal issues, but there really isn't any liability. In fact, I know a lot of growers that pride themselves on keeping older parts of the plant that have since senesced and dried and withered as a testament to how much this plant has done over the years.
Jane: That's an interesting one. If you do want to take them off, it's best to wait until they really are brown and crispy and then the plant's taken everything back that it possibly can, but it's interesting that there are people who leave those on. I hadn't heard that. I suppose the only other danger is that you leave the leaves on thinking that they're just undergoing senescence when actually the leaves are falling for some other reason, such as over-watering, and you end up with another problem, but I guess that's about diagnosis, right?
Matt: Right. I think, even from an aesthetic standpoint, if you want to clip them earlier before they fully withdraw and if you're taking care of the plant, it's not like they're living on the slim margins that they live on in nature in our home. Hypothetically, if you're doing well, they're pampered, and so even taking off half-senesced leaves with some green still left on them isn't going to make a huge drain on the plant unless you almost completely defoliate it in the process.
Jane: It is really cool the way that the plants do this. I'm thinking of my Streptocarpus, specifically in the winter time. Some of them have what I think is called the line of abscission, where you can see the top half of the leaf, furthest away from the petiole, is really yellow and then you've got this literal line and then a green section. It's like the plant is almost pulling back the chlorophyll in a line?
Matt: Yes, you can see that distinct layer between what the plant is valuing and keeping going and what it's trying to do away with at that point. That whole abscission layer becomes extremely obvious. In deciduous trees and temperate areas, you can actually look in some species at the base of the leaves see this corky growth that was grown in between the leaf to cut it off from the rest of the vascular tissue. So the plant is very intentional with its actions when it comes to leaf senescence in that way.
Jane: I'm thinking, this is a slightly weird one, but I was collecting beech leaves recently from a beech hedge for my daughter's isopods - we've recently got an isopod culture in the house.
Matt: Nice!
Jane: Yes, it's great actually! I have to say I unexpectedly find them really interesting. Well, actually, that's not unexpected, but I like them a lot more than I thought I was going to like them. They're very cute.
Matt: Alarmingly charming.
Jane: They are! They're really great. Anyway, we were collecting these beech leaves and I knew that beech leaves would be a good choice because they're still on the hedge, so they haven't been on the ground and picking up potential problems, or hitchhikers, and I knew they'd still be on that hedge because beech leaves have this habit of holding onto those dead leaves until the new leaves come through. I'm just wondering why beech specifically do that and hold on to those leaves until the new growth comes through?
Matt: Certainly is actually - it's a great observation and it's cool to hear that the European beeches do it as well because our Eastern North American species does the same thing, as well as some of our oaks. The phenomenon you're describing is referred to in the scientific literature as marcescence and it's actually hotly debated as to why the plants are doing this. What they do know about it is that it tends to happen lower down on the tree and it tends to happen more often on younger trees. So the leading hypothesis, or at least the one I favour, is that these are trees protecting their buds while they're at convenient nibbling height for herbivores, like deer. The fact that it's specific, at least around here, and in your case, to beech trees and in some oak species, says a lot because those are species that are pumping a ton of tannins and lignin into their leaves. They don't easily break down. So the theory goes that by loading the tips of their branches with these dead husks of the leaves, it's making any herbivore think twice before it takes a big mouthful to get at what is essentially tiny buds. The fact that there's a lot of tannins in there means that in any mouthful, if there's a lot more decaying leaf material in there than there are edible buds, those tannins are binding to tissues in the stomach and potentially keeping whatever's eating them from gaining any nutritional benefit from it. Again this is just a hypothesis but it's the one that I think makes the most sense from an evolutionary standpoint.
Jane: That's really, really interesting. So I wonder whether the fact that it's a hedge and that perhaps the plant is kept juvenile by the constant cutting of the hedge, would that be a factor in it?
Matt: Yes, it's certainly possible. It would be a fun thing to let a section grow and keep one section... if you had the space and time to do some experiments.
Jane: Funnily enough there are loads of beech trees in the same park. I need to go and see if they've still got their leaves on as well. I'm not sure I'm gonna go and check that out but, yes, it's amazing, when you start observing these things, what you learn. I'm always learning something new from plants, which is great. Let's just go back to dormancy, I've taken us off on a tangent as usual! We've talked a bit about the definition, so that must mean then that there are different degrees of dormancy? I'm thinking of my Oxalis triangularis which lost all of its leaves over the winter time and is just starting to re-shoot, as opposed to something like my cactus and succulent collection. Most of my cacti have not been growing over the winter but they haven't got leaves, but you know, the succulents have got leaves, they haven't lost their leaves they're just sitting there waiting. Presumably that's just two different types of dormancy?
Matt: Yes, it's all dormancy in the bigger picture of things, but I think dormancy is also a function of where these plants are coming from and their life history strategy, so to speak. So an Oxalis with lots of leaves that it can reproduce year after year, they're cheap, leaving them out would risk damage during seasons where growth really isn't all that beneficial and so dropping them makes a lot more sense, but for a succulent or a cactus, either if that's succulent leaves like an Echeveria, or a succulent stem, like a cactus, those are also water storage organs, so their growth tips may not be expanding and adding new growth to that but they hold on to those tissues longer because that's what's going to give them the one up when favourable conditions return and they need to start growing again. So it's dormancy but I think a lot of it's driven, both in appearance and effect on the plant itself, by the habitats that they're coming from.
Jane: That makes perfect sense and I guess that's why plants that come from climates where there's not much seasonal variation don't really need to demonstrate that dormancy because things aren't changing, they're just going to keep on growing year 'round because the light levels are the same and the temperature is the same. Does that make sense? I'm just thinking of all my Aroids and the fact that they do keep growing over the winter even though obviously, in my house, they're getting a bit less light.
Matt: A little slower? Yes, dormancy is entirely to escape unfavourable conditions. In the temperate zone, it's winter, everything freezes, sensitive tissues are easily damaged and even if they could be growing there's really no water because it's all locked up in ice, so that's getting them through the harsh winter conditions. In seasonal areas, even in the tropics where you get a pronounced dry season, you can get dormancy there. Some herbaceous stuff will die back completely, woody stuff often just drops its leaves but even evergreen things can go dormant like you saw with your cactus, but I think a lot about Rhododendrons, for instance, at least the evergreen species, they just stop all metabolic activities, or at least slow it down to the point where they're not doing much other than maintaining. It's all just escaping harsh conditions and that looks different based on where you are geographically.
Jane: That makes sense, so, in other words, when I'm thinking about whether a plant needs dormancy - because I often get questions from people saying, "Does this plant need to be dormant? Does that plant need to be dormant?" -- really you need to have a look at its native climes, to assess whether it needs that dormancy based upon what's happening at different times of year and what the plant might be expecting to undergo. In terms of this temperate plant, it's expecting to be going into a cold British winter and lose all its leaves and then pop back up from its corms or rhizomes in the spring, compared to the cactus which is just going to sit there and wait for things to improve.
Matt: Yes, I can't really think of any example where you could just look at a plant and make a prediction about its dormancy needs. You definitely have to do your research, which I encourage you to do regardless of what you're aiming for. Learn something about where these plants come from. What's the seasonality like? What conditions would they experience in the habitats that they're native to? The cues for dormancy vary. Sometimes it's day length, other times it's temperature extremes. It could be completely hormonal and there's flexibility in that. So, for instance, due to climate change here, our falls and springs are getting much more mild, so plants go dormant later and wake up a little bit earlier, but they still, being from a temperate zone, have that evolutionary momentum. I guess you could say, to require dormancy, in fact, plants from temperate zones, most of the time, absolutely require that dormancy period, depending on how long it is in order to maintain themselves long-term.
Jane: That's a really good point. So plants must have some internal body clock to know when they are... how are they doing that? Is that just by sensing the conditions changing? We're getting down to heavy botany here, but is there a way you can explain that to me in a way that even I will understand!?
Matt: Sure, and it's going to vary, and to be fair, I don't fully understand and I don't think actually most scientists studying it on a daily basis...
Jane: That's reassuring!
Matt: Yes, I like the never ending mysteries of the plant world but, yes, usually, I would say, it's most often environmental cues. So, for any of the temperate species that I like to grow here, or that you're growing over there, generally speaking it's going to be the chill period and so they measure it in the same way the plant would perceive relative day length to night length. It's how many hours, or days, in a bigger sense, are you experiencing very cold temperatures versus warm temperatures? So as that length starts to grow, more cold temperatures, then you're getting warm temperatures, that's a cue that we're heading into a season defined by extreme cold and ice. Sometimes that's also day length too, that can also influence it, so as the days shorten that's another cue to a plant to say we're heading into the coldest months of the year, time to start winding things down. Again, it's going to vary. The hormones involved are pretty complex and I think we're still discovering which ones are involved to what degree, but I think a lot of it is a mix of environmental cues and just hormonal rhythms within a plant based off those.
Jane: Presumably it varies whether dormancy, or a lack of dormancy, impacts on the plant? I'm thinking of some people growing succulents don't really change their conditions in the winter and just keep them at the same temperature and light levels. Presumably those plants are able to cope with that, whereas perhaps a plant from a temperate region that's expecting to lose its leaves over the winter might have more of an issue, it just depends on the species and so on?
Matt: Yes. If you try to keep most temperate species going, even if you could somehow fight their innate ability to just go dormant, you would burn them out. It would just be like keeping that flame going at high speed all the time. It's almost like they need that rest period. For a succulent from a desert that doesn't really get a ton of seasonality, maybe it does have a rainy season, I think those conditions are more tied to just the local growing conditions and so if they stay favourable, say you're growing these in a warm house under heavy powered lights during the winter, and, like you said, don't really change much, you could keep those going probably to infinity and beyond, provided, again, you're meeting all of their other needs. Again, it goes back to the habitat and the environmental cues that they're relying on to go into dormancy and what they would experience when they do decide to go into dormancy.
Jane: Like all things it's experimentation and everyone's home is going to be different. I'm sitting here with my cacti and succulents, which I have watered a little bit this winter but they haven't had much, and I'm teetering on the brink of maybe giving them some water, but certainly the Agaves in my unheated greenhouse will not be watered for a bit yet because I live in fear of the collapse. I've seen so many, especially this winter, I think it's been a harsher winter here, and I've seen so many people posting pictures on social media of cacti when you touch them and they just dissolve, and really tragic images of, like, succulents that have suffered. So I'm not going to break mine out of dormancy too early because that might end really badly. I've done quite well this year. I've got one dodgy-looking Agave, but it's all going so well!
Matt: They'll recover, I'm sure.
Jane: Well, the next challenge is bringing my cacti and succulents that have been inside out to the greenhouse without them getting sunburned because, obviously, they've been used to being inside, so that's the big one where I have to have the fleece ready to be shuffled about. The challenges of being a plant parent are considerable, but hey, it's all part of the fun!
Matt: The spring is always this delicate balancing act of, "Should I water? Is this enough light? Is this too much light?" Oh god!
Jane: Yes, it really is! It's a tricky time. I like plants that have a bit of a rhythm to them and do die back. I think it's fun! I guess that's why I like the Gesneriads, like Smithianthas and things, just because, right now, they've been dead in a pot for a while and then I'll just start watching them again and they'll spring out, which is fun, but I know lots of people don't have the places to store pots of soil with nothing in them.
Matt: Highly limited by space!
Jane: Yes, exactly.
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Jane: Thanks to Matt for giving us the lowdown on dormancy and we'll be hearing about Matt's book at the end of this episode. So, we've covered the plants that are taking a break temporarily, but what about the plants that are taking a permanent break? As I often say on the show, killing houseplants is like death more generally, part of being a human being and nothing to be ashamed of. It's a learning curve, we're all on that curve somewhere, but it doesn't make us feel any less bad, particularly when it's a plant that's precious to us.
A few weeks ago, I put up a post on Instagram with a picture of a beautiful Staghorn Fern that I had killed. I don't know why I'm laughing, it was absolutely tragic! I left it outside over the summer, it was very, very happy and then I forgot to bring it in on an unusually frosty night in late summer/early autumn and that beautiful Staghorn Fern was no more. I've regretted it ever since. What was great about this post is I was trying to get across the fact that we all kill plants. Sometimes it's a silly mistake, sometimes it's down to a lack of knowledge, sometimes it's pests. There are many reasons why plants die and it really is okay, as I often say on the show. I wanted you guys to share my pain and, duly, you did, with lots of great comments. I'm just going to read out a few of them now for you to share the pain. Cue the sad music!
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Jane: TheSilverCricket writes, "I killed an arrowhead plant of an especially nice variety that was originally from my grandmother 34 years ago. I still think about that plant." DGA_Plants wrote, "I killed a massive Echinocactus grusonii that had been given to me. It must have been 30+ years old. It'd have been fine in my greenhouse for a few years, but last winter it just rotted." Man, that's a brutal one. Echinocactus grusonii, that's the Golden Barrel cactus just in case you didn't quite get the Latin name there. MorganCole, "The gorgeous Pilea my mum has now given me two of! I just can't seem to keep them and I adore the leaves". Well, hopefully your mum's got a few more she can give you, MorganCole. HouseplantsXYZ wrote, "I have one of those small greenhouses from Lidl and I forgot to open it one morning, it was a warm sunny day, when I finally remembered it was, like, 70C inside that tent. A few of my succulents just melted, including a five-year-old Crassula that I grew from a leaf. I did manage to save most by taking cuttings of what was left from the main plant." ChickenKnickers writes, "I'm gutted I kept buying Calatheas even though I always kill them, so no more Calatheas!" I think that's probably sensible ChickenKnickers, although I wouldn't be surprised if you got dragged into the Calathea network again - unintentional pun there!
SweetGreets writes, "Crassula Buddha's Temple, Begonia Rex, Alcoasias, but the ones that have survived have brought me so much joy. I just won't be getting any Alocasias or Begonias for a while!" AltogetherElsewhere says, "Probably the big beautiful Callisia repens that I grew from discarded cuttings left outside all summer and brought in for winter just a few days late." The FernFeeler writes, "I was very stressed, working 60 hour weeks, dead on my feet and plant care was pretty much last on my priority list. So one night I staggered out to my patio, where my plants live, to make sure nothing was dead and panicked when I realised my air plants are at least a week overdue for their soak. Luckily for me there was a full bucket of water nearby. Score! I dumped my giant four foot long Tillandsia usneoides in to soak overnight and stagger back in to collapse on the couch. Cut to the next morning. I go to retrieve my lovely fresh, hydrated baby from the bucket, then the smell hits me. Apple, cider, vinegar! That bucket was not fresh water but a strong vinegar solution to kill some weeds and use as a disinfectant, which I never got around to emptying. I now had a giant pickled air plant. I now refuse to work such long hours. I love my rest and my plants too much!"
There were some heartbreaking tales in there. Thank you to everyone who shared on that thread on Instagram and if you want to read everyone's contributions, I will put a link to that in the show notes. Now it's time for some shoutouts! New Patreons this week - there's loads of you - Natasha, Jonathan, Tom, Esther, Alex, Gillian and Kerry all became Ledge-ends and Rebecca, Chicken, Elaine, Melanie and Jenny became Crazy Plant People! Thanks to all of you for your support. It's good timing because it means you'll be able to join us for the Patreon-only Zoom session which is Sunday 28 March, 2021 at 19:00 BST. I'm not going to try to translate that into any other time zones because I know our clocks go forward the previous midnight and hence it's all a bit confusing, so check your time zone, if you Google it you should be able to find out what 19:00 BST is where you are. Join us on Zoom - if you look at the latest post on Patreon, there is a link where you can come along and hear me talk and ask questions and that's for Patreons of any level, from Crazy Plant Person right up to SuperFan, so please do join me!
Thank you to FairyFlowerMother in the US for leaving a lovely review on Apple Podcasts. I wanted to give you an update on my book Legends of The Leaf. Somebody commented that I hadn't mentioned it of late. I'm sorry about that! I've had lots of pots on the boil, as you might say. The good news is that I am ploughing through! We're at 476 supporters, which is 73% funded, so close to being three quarters of the way there! I've definitely seen some familiar names on the pledge list recently, including Anthony Peterson - I know you're a very dedicated listener and Patreon, so thank you! Grace, I see you've upgraded your pledge - thank you for that. Alice and Ada, you're all on there! I'm sure there's loads more other names on there that I haven't been able to spot, but thank you to everyone who has pledged recently. People are asking when the book's going to come out. Well, I can't get on with the book until I'm 100% pledged, so now that my kids are back in school and I have a tiny bit more time, I'm going to be working hard to spread the word about Legends of the Leaf, so please do help me with that and let other people know about what the book is about. It's going to be great fun!
As I said on Twitter the other day, if you want to find out which houseplant was part of Nazi World War 2 research, which plant is eaten by Japanese people as tempura and why it's very unwise to eat an unripe fruit of the Swiss Cheese Plant, then this is the book for you. If you want to find out more, visit my show notes at janeperrone.com and click through to the link to unbound.com where you can make your pledge. So let's make it happen!
Thanks to those of you who've already sent in your voice memos about The House Plant Expert by Dr. David Hessayon. I'm still looking for more of your thoughts on this. If you really, really don't want to be putting your voice on the air, then you can send me a regular email with your thoughts and I can read them out, but I'd love to hear your voice, so please do send that through: ontheledgepodcast@gmail.com You can just use your smartphone to record and that way we can find out what it is you love about Dr. David Hessayon for that upcoming episode and you can hear your comments alongside those of a certain Mr James Wong! I'm also still looking for questions for Terry Richardson, aka The Black Thumb, about orchids, so if you've got a poorly orchid, do drop me a line with your question and I will put that to Terry for an expert answer.
Now back to my chat with Matt and I wanted to find out what exactly was going to be in this new book, 'In Defense of Plants'!
Matt: I think I've set out a goal for having a linear start and finish to it, but telling stories that fit in all along the way. So I start with my introduction to botany, and how I realised plants are amazing, and then I use that as a jumping off point for all the ways that I find plants are doing amazing, sometimes very familiar, things but also very alien things for what we expect out of the living world. So I start going into flowering, dispersal, fighting, parasitism and carnivory and just explore all of the really cool examples that I could come up with, or handfuls I should say! It was harder to pick which ones get included and which ones I couldn't include, just based on my length limitations. So it's storytelling with a directed narrative.
Jane: I'm not expecting you to spill everything, but can you give us one or two little juicy facts from the book that we might be able to read further about?
Matt: Sure, yeah, and actually some might involve orchids that you and your friends over in the UK would probably be pretty familiar with - the Bee Orchids and the genus Ophrys. They're terrestrial orchids that I think generally grow at higher elevations, but they produce some of the most extravagant flowers. Then, when you put them into the context of what pollinates them, that extravagance makes a lot more sense because they're pollinated by the males of different bee and wasp species. So when you start looking at who pollinates what flower, not all the time, but a lot of the patterns start to look a lot like females of those species, which makes you start to scratch your head and then when you watch the males interact with the flowers you realise, "Oh, they're trying to mate with them!" and so there's been all of this really cool chemical analyses done, on what each flower is giving off and they're finding that, in a lot of cases, these flowers are emitting the same or very close mimics of the female sex pheromones of those bees. So there's been all of this debate as to how many species are in this group and what's causing all of this diversity and they're finding that all it takes is one tweak in the pathway of how these scent compounds are produced within the plant, to make an entirely different compound! Because of the specificity of the pheromones within different bee species, you get one tweak that changes and suddenly it's attractive to a completely different species. You have reproductive isolation because that bee is only going to that flower and now you have what is essentially a new species almost overnight. So stories like that are really exciting because it paints this picture of Kumbaya pollination. It's the most altruistic thing in the planet... no, it's all the plant trying to take as much as it can by giving back as little as it can in return. Few offer such a good example as the orchids because there's really no reward and the more time that a male bee spends mating with the flowers, the less time it's mating with actual members of its own species, so it's almost sinister. Obviously, there's no real emotions like that in the plant world, but it is pretty wild to think about!
Jane: Yes, there are some really cool orchids. In fact, I live in the county of Bedfordshire and I do have a book called Orchids of Bedfordshire, which I'm going to go and have a look at. The only orchids I've ever seen in the county of Bedfordshire are ones outside a branch of Go Outdoors, which is a chain of shops where you go and buy tents and walking boots there. It's such a weird location! It's like. 'Why!?'. I just saw them in a patch of grass outside there and I was just thinking, "That's strange!". But there you go! That is the way that nature works: these things pop up all over the place, but that is fascinating.
Matt: That's a great patch of grass.
Jane: I am that woman who was lying on the grass outside the builders merchants on the industrial estate because there's a really good patch of Sweet Violets flowering at the moment, which I go and check every year. My children are like, "Mum, would you stop sniffing the violets?" People think you're doing something strange lying in the grass on the side of the road! That's what we do for plants, isn't it? I'm sure you have done similarly outlandish things over the years to get to see something interesting!
Matt: Yes and luckily most of the time I'm in nature doing it, but now that I live in suburbia, my neighbours get to see all my weird plant habits!
Jane: Exactly! You've obviously been making In Defensive of Plants for quite a few years. What is it like, condensing all your knowledge into a book, as opposed to making a podcast?
Matt: It was a mixed bag. When it was first presented to me as an option, I realised I would be silly to say no to it and so I became immediately overwhelmed because I was finishing up my PhD, writing up my dissertation, and I was, like, "Oh cool! Another thing I can add to my daily list of to dos!". But once I got over the hump and got into a groove with writing, it became a lot of fun. In a lot of ways, the podcast is similar to writing a book. You're just a curious person looking for answers to questions that you have and talking with really interesting people because one single person is not going to have all the answers, or even a portion of the answers that are satisfying. So, being able to talk and explore different avenues, you unlock ideas you don't even realise you had, or questions you even had in the first place! It does differ in the fact that, week after week, I sit down with interesting people and ask them the questions and then they get to distill the science to me in the way that they deem it important or relevant to what they're asking. Whereas when you're writing a book, or anything for that matter, you have to find that stuff for yourself and distill it in a way that you're not getting a lot of help, you're just taking the science and trying to make it as understandable as possible, which is where having good editors comes in. They rein you in and say, "Okay, you're way out in the weeds on this one!" or, "No you can go into a little bit more detail about this". So it's different in that it's really just my voice the whole time, which is really uncomfortable in a lot of instances. It makes you feel very vulnerable at times. When people bring questions or issues about the podcast, like, I say, "Oh well, go to the source. I gave you all the contact information, go talk to the people that do this science," but if people want to explore more, or ask me questions, or say something about the book, well, then I'm at the front of that and saying, "Okay, well this is how I interpret it. How would you interpret it?" - that sort of thing. So there's a lot of fun nuances to both. There's a lot of overlap, of course. The podcast gave me so many ideas that ended up in the book, but it's pretty different in it being solely your work.
Jane: Your podcast's been going... how many years has it been going now? I'm going to guess, has it been going on for six years?
Matt: Yes, it's about six years at this point. Good job!
Jane: Oh, that was good, because I'm thinking you started a couple of years before me, so that's about right! Obviously, your mission is to get everyone to appreciate plants - I'm not putting this all on you because obviously there's other people working on this too - but do you feel like plants are starting to move up the agenda in terms of being recognised as the amazing things they are?
Matt: Great question and in so many ways I think we're making headway. Of course, it's a big, royal 'we'! I am not alone in this, nor should I be! We're all in this battle together, to try to bring plants to at least a portion of the forefront of people's attention, but I think it's working. I gauge the response based on the emails that I get from week-to-week and when I first started it was all academics or people that were really into plants already, sort of the choir. As I've gone on and done topics with different people, done a lot of crossovers, you start to hear from people that almost start out the emails verbatim, like, "I was never into plants" or, "I never considered plants before and now I'm listening to your podcast" or, "I'm reading this person's book..." and you start to get the sense that, I think, the importance at least, surrounding plants, is starting to come to people's attention. A lot of that has to do with the other charismatic organisms, like bees and monarchs, that absolutely rely on plants. I think people are starting to make those connections, "Oh, plants are habitat and we're losing everything because of habitat loss, so maybe there's something to plant," but also both a blessing and a curse. The pandemic has taught people that they can find, or they have to find, ways to amuse themselves in and around them, in their home, or risk severe depression as a result. I think a lot of people have solved that issue through gardening and in houseplants, and outdoor gardening if you have the ability to do so. Whether you're interested in it because you get food, or it's just some nice stuff to have in your house to look at, or you really do get into the botanical aspects, or the way plants interact with the world, I think people are slowly coming around. It's always you take the good with the bad. There is a surge, as you hinted at earlier, with a lot of misinformation going around. I'm not going to point fingers at houseplant groups on Facebook, but I think I see a lot of...
Jane: Point away!
Matt: There's a lot of misinformation going around at the same time, which, again, at least people are interested in thinking about this stuff, but there's a lot of bad sources out there and just because someone can keep S**ansevieria alive and has a nice Instagram account doesn't make him a houseplant expert! So you've got to take the good with the bad and all I can do at the end of the day is, I never want to pile on, or call anyone out, or put anyone on blast, that's not why I'm here, I just want to inspire people and if I put out a resource that's welcoming and inspiring and people can latch on to at least parts of it at times, then I think I've done my job.
Jane: Absolutely and it's interesting, you're right, what are the ones I've seen this week? Shaking your fiddle-leaf fig seems to be popular right now.
Matt: Okay...
Jane: I can see where it's coming from, but I think you'd have to have it next to you, shaking it all day, in order to replicate any natural movement that was coming about through wind strengthening the trunk! How long are you expecting to shake for? I don't know, I know there is science about stroking seedlings being beneficial but I don't know about scaling that up to a tree, but that's one! Then there's also the pasta water one - watering your plants with the water from your pasta!?
Matt: Like starch water?
Jane: Yes, like starch water, which, again, I'm just like, "Just use fertiliser!" People have spent a lot of time and research making bespoke special houseplant fertilisers that have got the right amount of nutrients in them, why are you worrying about pasta water?!
Matt: That just seems like a great place for bacteria and fungal... like, not good ones!
Jane: Yes, exactly! It's just a bacteria fest, isn't it?
Matt: Yes.
Jane: The other one I saw today was somebody saying that somebody had recommended to them that when they potted up their Hoya, that they put an egg underneath the root ball.
Matt: Oh, god, no!
Jane: I don't know if that was a smashed egg or a whole egg, but I was just like, "That's going to stink!"
Matt: That's going to be really gross and the whole eggshell thing in and of itself is so blown out of proportion. The amount of grinding you'd have to get eggshells down to, and the amount of time you'd have to invest in amending even small amounts of soil, I think it's largely overplayed. It's the same thing as human health - everyone's looking for shortcuts, everyone's looking to put their own little spin on things. There's good information in there sometimes and oftentimes it's coming from good intentions, but take a step back, realise people have been at this for a very long time and there is a boatload of resources that have been tried, true and tested over time and maybe what this person's just reiterating from another person that they heard it from, who's reiterating it from another person they heard it from, isn't the best. They might be charismatic but they might not be the best source to go to.
Jane: I guess the other thing is that houseplants are tough and so, if you do water them with pasta water, they'll probably be okay, but that doesn't mean it's a good idea.
Matt: That's the other part too is most of the stuff you're encountering that's readily available, unless you're getting into really esoteric stuff, has stood the test of time in terms of if it's marketable and economically viable, it's probably not that picky because it's mass-produced and can handle the conditions that most people, us common folk, are throwing at them in our houses and apartments. So you even have to ask yourself how much of this is even necessary if you use decent enough compost in your mix? We're always asking my buddy, Dave, "Should we re-pot this? He's like, "Well, do you want it to grow to twice its size? If not, then don't bother. If you do, then give it more." You've got to gauge your situation.
Jane: Yes, that's very true and you do hear these stories of great grandparents who've got this Begonia, or something, that hasn't been repotted in 25 years and it's the size of a house and things like that! I've got plants which I haven't repotted and they're in pots with no drainage and it really shouldn't work but they're absolutely fine.
Matt: Exactly.
Jane: We all break the rules sometimes and it works but ...
Matt: I'll say this: I will keep the most finicky, weird plants alive, no problem, but I can kill a dumb cane or a Pothos tomorrow if I just look at it the wrong way! Even "easy stuff" can be challenging, depending on what your interests are and how much attention and what soil mix it is. Again, it's so case-by-case.
Jane: I think there's a lot in the fact that it depends how much you like the plant. I think the reason why you can't keep the Pothos alive is because you don't really care! You're not going to put the effort in. I find this with plants... when somebody gives me, and this happens about once every other Christmas, somebody gives me a poinsettia, I'll be like, "Thanks!" and it will die because I really don't have any motivation to take care of it. Whereas a plant that's a little bit tricky that I really love, I will put a lot of work into and thus it thrives.
Matt: That's a really good point, Jane. I wonder if the most common houseplants in my house, growing up, were Pothos and they're a dime a dozen. Any time I want more, I can just call my mom and she'll ship me a cutting, so I wonder if I just take it for granted. I feel bad, but also there's a never-ending supply from her house which also makes my jaw drop when I see people spending any money on a Pothos, ever!
Jane: I know! I've just been looking at Hoya prices for some of the Hoya cultivars and just been jaw-dropped looking at that. It's supply and demand.
Matt: Hey, if it means weird plants are going for cheap, like I just got a beautiful Cycad, a giant one at that, for $40 and the tiny Anthurium that was being sold next to it was in the triple digits, so I was like, "Hey, if you guys want to take the boring common stuff and pay a lot of money for it which means all the weird stuff I like is cheap - cool!"
Jane: Yes, exactly. I think that's the benefit of not going with the crowd and liking what you like, which is not necessarily a thing that's at a premium. I'm glad that I got a lot of my Hoyas a while ago now though.
Matt: Got it before it was cool.
Jane: I can now be chopping and propping and making a fortune, not that I'm going to obviously, given that I proclaim to be all ethical about this stuff. I think you've just got to like what you like and what makes you excited and that's the main thing.
Matt: True.
Jane: That's a great note to end on and thank you very much for joining me, Matt, and for shedding some light on the mysteries of dormancy and also telling us about your book.
Matt: Thank you so much for having me, Jane. It's always an honour to be on here. I love what you're doing and it is always a complete and total pleasure chatting with you! I really enjoy it, so thank you again.
Jane: Thank you, Matt!
[music]
Jane: Thank you so much to my guest, Matt Candeias. Do go listen to the 'In Defense of Plants' podcast and check out his book. All the details will be in the show notes, as always. That's all for this week. I'm taking next Friday, 2^nd^ April, off for Easter, so I will see you in two weeks, on 9^th^ April. Thanks for joining me! Bye!
[music]
Jane: The music you heard in this episode was Roll Jordan Roll by The Joy Drops, Never Come Back by Soft and Furious, A Man Plays Trekking Song on Fewa Lake, **Pokhara by Samuel Corwin and Time To Move and Motivate by The Insider. All tracks are licensed under Creative Commons. Visit the show notes for details.
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Is my plant taking merely resting, or is it dead? Why has my cactus stopped growing? If you’ve ever asked yourself these questions, this episode is for you! Botanist Dr Matt Candeias joins me to demystify dormancy in plants.
Missed the first four parts of the leaf botany series? Listen here.
This week’s guest
Botanist Dr Matt Candeias is creator of podcast In Defense of Plants. He has just published a book in the same name.
(You may remember Matt from episode 39 of On The Ledge and Midweek bonus 2 where we discussed the film Little Joe.)
Check out the show notes below as you listen…
Matt’s book is published by Mango Publishing.
Matt’s new book, In Defense of Plants, is published by Mango: you can read more about it on Matt’s website.
If you have missed out on previous leaf botany episodes, catch up here.
Want to know more about meristematic tissue? Britannica explains it here.
Want to see a line of abcission? Check out this post on ThoughtCo.
Marcescence is where plants hang on to dead leaves - like my beech hedge. There’s a good guide here.
Interested in isopod cultures? I am going to do more on these in an upcoming show, but for now, here’s the video that inspired my daughter, from YouTuber Snake Discovery.
Want to see the responses to my dead fern Instagram post in full? They’re here - and the staghorn fern is pictured below.
My staghorn fern. RIP. Photograph: Jane Perrone.
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CREDITS
This week's show featured the tracks Roll Jordan Roll by the Joy Drops, A Man Plays Trekking Song on Fewa Lake by Samuel Corwin, And Never Come Back by Soft and Furious, and Time To Move and Motivate by The Insider.
Logo design by Jacqueline Colley.