Episode 148: leaf botany part two - CAM and guttation explained

Guttation. Photograph: Scot Nelson on Flickr

Transcript

Episode 148

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Jane: Hello and welcome to On The Ledge podcast episode 148, your one-stop shop for houseplant chat. This week's show is a smackdown between two plant processes in part two of our leaf botany series. Botanist and On The Ledge listener Dr Polly Schiffman is on hand to answer all your questions about what CAM (crassulacean acid metabolism) and guttation actually are. So if you heard those Meet the Listener questions and wondered what on earth I was talking about, this is the episode for you. Plus, I answer a question about beheading a Chinese money plant and we hear from listener Joe in Texas who will be answering that tricky question CAM v guttation in Meet the Listener.

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Jane: Now it's time to sit down with a cup of your finest English builder's tea, served in a Cornishware mug, only Cornishware for me! If you're not aware of what the hell Cornishware is, then have a Google, or an Ecosia, I should say, and you'll find out. Anyway, I'm waffling now but I want to talk to you about some reviews that I've had. Let me just whet my whistle as we say here in the UK. Four reviews have come in and they are delightfully varied in their content matter. We'll start at the bottom and we'll work up in terms of the pleasantness of these reviews. The one which was the least flattering but made me laugh, is entitled: "If you want to talk politics, at least get it right!" The reviewer is called WhyAreYouOnlyOniTunes - I guess that's not a personal dig because On The Ledge is on many Pod Apps, but anyway, WhyAreYouOnlyOniTunes said: "BLM, (which I presume is short for Black Lives Matter) is a front; an organisation that funds white democrats and uses black and minorities as its foot soldiers. Look deeper Perone." Perrone spelt incorrectly, with one R. I'm not going to honour your comment with any kind of response because it's so ridiculously out-there and I just simply cannot trust somebody who cannot even get a surname spelt correctly. Interestingly though, you did give the podcast three stars, I guess you're enjoying some other elements of the show but thank you for your review.

I had a lovely review from Miniki8 in the USA whose title is: "Jane is great, love this podcast. I wish I could pop in at her house and get some plant cuttings." That is so sweet. I love giving out plant cuttings. If everybody who listens to the show comes round, it's going to get very crowded, so maybe not on this occasion!

Also, NewPinterestUser, from the US, is my newest fan, apparently, so thank you for your lovely review. PlantRescuer says: "My favourite podcast ever! Simply obsessed." Thank you PlantRescuer, I think I know who you are and you may be featuring in an upcoming show! I'm giving too much away here. Is that all of them? I think that's all of them. The most recent ones anyway. Have I read out JayBekEm's review, "I'm in love with this show. Wonderful British humour paired with interesting plant information"? I'm not sure, I can't remember, but if not, thank you JayBekEm and do go and leave a review for On The Ledge because all of your reviews make me smile, even the misspelt three-star ones and it's a delight to read them, so thank you to everyone who has reviewed the show. Whether that was in March 2017, just after the show started, or just last week. I appreciate all of your reviews!

Don't forget to join Houseplant Fans of On The Ledge, our über-friendly, welcoming houseplant fans group for anyone who listens to the show. Do answer all three questions because my moderators, they are tough cookies! They will not let you in unless you answer all three questions, but once you're in it's a wonderful place to be, with loads of helpful members who are ready to commiserate with your disasters, answer questions and generally share the houseplant love. It's Houseplant Fans of On The Ledge. You can search for it on Facebook and it is bound to pop up and you'll know exactly where you're going.

Thanks to Sonya, from Australia, who sent an email in thanking me for the way I handled the criticism of the Black Lives Matter mention on the podcast. I've had a few emails like that from people, so thank you very much for your support. Sonya also recommended the plant ID app EUCLID for identifying Angophora, Corymbia and Eucalyptus. She writes: "It really teaches you the importance of considering every aspect of a plant to get clues and positive ID, so do check out EUCLID!". I shall certainly be doing so.

Thank you to Kristin for becoming a Crazy Plant Person, Christine, Amanda and Emily for becoming Ledge-Ends. They've all become Patreons in the past week or so - great to have you on board, one and all. If you're not quite sure what all this Patreon business is all about, do check out the show notes at janeperrone.com where all is explained and if anything isn't explained, you can always drop me a line and I will be happy to help.

Just a reminder there's no episodes running on July 24 and July 3. For the first time since February I'm taking a break from the show. It'll be my first days off in many months, so I'm really looking forward to that time. I'll be back with the show for episode 150 on 7th August. Do keep coming forward for Meet the Listener. We are still looking for people to feature on the show. So, if you are a from a country or a region that has not yet been represented on Meet the Listener, then I'd particularly like to hear from you. All you need to do is drop an email to ontheledgepodcast@gmail.com and my assistant, Kelly, who takes care of Meet the Listener, will be in touch with full details of how to take part. It's really, really simple - you just need a smart phone and a voice. That's it!

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Jane: Let's start the show with Question of the Week, which comes from Tracy. It's a query about her Chinese Money Plant. It's now 24 inches tall. How much is that in centimetres? 60cm tall, for those of us in Europe, who prefer metric. Tracy wants to reduce the height of the plant without killing it off. Pilea peperomioides, or the Chinese Money Plant, does have a habit of doing this. When you get one from a friend, or you buy one in a shop and it's cute and dinky and small, little do you know that this plant can actually get quite tall and lanky and then can end up toppling over. The interesting thing to note, in nature, these plants do just that where they grow in China, in Hunan Province. Once they get too tall, they do just flop over and I guess that's one of the reasons why they root so easily because you can then get baby plants growing from the stem which can then root into the ground. The parent plant might get killed off or not, and you end up with a little forest of plants. Those of us who want our Pilea peperomioides to look a little bit more ordered, what do we do? This is a question I'm facing with my own plant at the moment because it is getting quite tall. I haven't quite made the decision what to do yet. My suggestion for Tracy was that either she let it flop, or perhaps supported it with a cane, or she went for the radical option - a beheading. This does sound rather serious but it really does work for these plants. You can cut the top off a Pilea peperomioides and then take off some of those lower leaves, pop that in either some water or into some soil and it'll root again fairly easily and you get two for the price of one because the existing plant will also start shooting again from that top growth. So if your plant really doesn't look great and you just want to change it, that is a radical way of doing it and it's pretty fool-proof. It's hard to get that wrong. If you're really unhappy with the shape of your Pilea, do consider this radical surgery.

How much do you chop off? Well, that's really up to you. You can take as little as 5cm, right up to taking the plant down to a little stump, it's really up to you how you want the aesthetics of the plant to look. If you're the kind of person that likes to let live and let it do its own thing, then that's absolutely fine too. I did hear back from Tracy that her plant has sprouted quite nicely and is doing very well. Don't be afraid to prune your plants radically if they aren't doing what you want. Most plants will respond really well to pruning, particularly in the Springtime, and early Summer, when they are just itching to grow. If this all sounds like sacrilege, then you can just let your Pilea do its thing. The babies will grow from the sides and also from the stem and all over the shop to be quite honest and that's absolutely fine. You'll end up with a healthy looking bush and that's all great, as I say, don't be afraid of some radical surgery. Make sure you use a clean, sharp knife and clean that before you move on to any other plants, but other than that, you should find that it works really well. If you've got a question for On The Ledge podcast do drop me a line - ontheledgepodcast@gmailcom - and I will endeavour to help. I will be doing another Q&A special in the next few weeks, so get those questions coming in.

Now it's time for our CAM and guttation discussion with Dr Polly Schiffman. Really glad to get Polly on the show to talk about this, as a loyal listener and, indeed, a Patreon. It's a bit daunting speaking to her because, as I say, she knows a heck of a lot more about plant biology than I do, but she was very generous with her time and gave excellent explanations of both of these processes, so settle back and enjoy leaf botany part two.

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Polly: I'm Polly Schiffman, I'm a professor in the biology department at California State University, Northridge which is in Southern California, in the city of Los Angeles. My expertise is plants and their ecology. I teach conservation biology and plant ecology and evolutionary biology and just love plants.

Jane: It has occurred to me that despite mentioning CAM and guttation regularly, and indeed mentioning them in the Meet the Listener questions, not everyone might be as genned up as we should be about what these things actually are. That's where you've generously volunteered to come in and enlighten us all. The first question I have to ask you, Polly, is the Meet the Listener question: CAM or guttation? Which is your favourite?

Polly: By far, CAM! No question!

Jane: This is where we're going to get deep in the world of CAM and guttation and find out what they are and why our houseplants are doing these things which, for some of them, are vital processes that are going on. Let's start with CAM, seeing as that is your favourite. It's my favourite too and it's an acronym short for crassulacean acid metabolism. What does that actually mean and what plants do this, because this is not something that all plants can do? Where do we start with CAM?

Polly: Crassulacean acid metabolism - it's named after a plant family Crassulaceae, which is what Crassula, Sedumand Echeveria are in. It's also found in other plants; a lot of succulents, including cacti, but all sorts of other succulents as well. Bromeliads are often CAM plants, as well as a lot of Orchids. So, those groups are mostly CAM and then lots of other plant families have a few species or genera that have CAM as well. So it's kind of cool that it's a type of photosynthesis that has evolved repeatedly in plants, independently in different branches of the plant family tree I'd say, so relatively unrelated group of plants have converged on this really interesting way of solving a problem that they have in doing photosynthesis in stressful environments.

Jane: That's what I love about CAM, is the fact that it's just they're so darn clever to have evolved this incredible way of dealing with environments that aren't really great. Tell us a bit more about how CAM actually works and what the acid bit means?

Polly: What I think I need to do, is back up a little bit and give some background about photosynthesis first. Most plants aren't CAM. They do regular old, what botanists call C3 photosynthesis, which is something like 90% of all plants don't do CAM. What plants normally do is they're taking water from the soil, usually, into their roots and then the water moves up through the plant and out the leaves through these tiny, tiny holes called stomata. The problem that plants face is this dilemma where their stomata need to be open because that's how they get carbon dioxide into their tissue so they can photosynthesise because carbon dioxide is one of the key ingredients for making sugars by photosynthesis. So they have to have their stomata open, these holes, to do that, but when the stomata are open water can escape out of those same holes as water vapour - it evaporates out. So, on a hot day, or in a dry environment, they're losing water but they still need carbon dioxide, so they're walking a knife's edge and the stomata can regulate the size of the opening and try and minimise that problem, but sometimes it's insurmountable. So what CAM plants do is they close their stomata during a hot time of the day, or during daytime, and they open their stomata at night when it's typically cooler and the humidity of the air is somewhat higher so they avoid losing so much water. What that means is their photosynthetic process, the biochemistry, is a little bit different than what most plants do because, yes, they're capturing sunlight during the day but they're not doing all the photosynthesis during daytime. Instead what they do is they break it up into a daytime part and a nighttime part. At night, they're transforming carbon dioxide, through a series of complicated biological and biochemical steps, into an acid called malic acid. That accumulates in their tissues, so as the night progresses their tissues get more and more and more acidic. During the day they transform that malic acid through some more complicated biochemistry and sugars. During the night the stomata are open, they're taking in CO2, they're using that through a complicated series of biochemical steps to make malic acid that they store in their tissues and then, during the day, they close their stomata, so they're not losing all that excess water and they transform that malic acid during the daytime into sugars. So they complete this process, it's just a more complicated process than what most plants do. Most plants don't have to face the extremes of the limitations that CAM plants do, with very limited water, living in deserts, or epiphytes where they don't have roots and nice moist soil. So, CAM plants tend to be the ones that dry out and are at risk of losing too much water.

Jane: I remember when I was doing a particular unit of my RHS course, the stomata are quite amazing the way they open and close. They've got these sausage-like guard cells that open up and close and I will put a link in the show notes to a diagram and a picture of that, showing how it works, because it is quite amazing how that operates, the stomata opening and shutting. Just the fact that they're able to regulate themselves in that way is just so clever, isn't it? When you're talking about CAM plants, do we have any idea whether CAM developed alongside photosynthesis or whether photosynthesis developed and then CAM was a later evolution? Do we know that, or is that something we haven't yet discovered?

Polly: That's something I'm going to give a good guess. I'm not totally certain about this, but my hunch is, actually now that I think about it I'm pretty sure, C3, the regular way that plants photosynthesise, is what evolved first. Because sometimes CAM plants are partially C3 plants and they can switch to CAM when they need to, when the environment gets stressful and then they switch back when they don't need to. Not all of them are so flexible, but some are. I'm pretty certain that the regular form of photosynthesis, C3, evolved first and then this more complicated specialisation happened later. There's another type of photosynthesis that we see most often in grasses, called C4. So there's even more complicated photosynthesis going on in the plant world. They all have, at their very core, this process that is essentially C3 with a whole bunch of other stuff tacked on, to make it CAM or to make it C4.

Jane: It's amazing, isn't it? Who knows what's going on behind the surface of our plants? It's interesting with CAM. I have seen people say that things like Sansevieria are good to have in bedrooms because of CAM, because it means that they're giving out oxygen at night. I suspect that the amount of snake plants you'd have to have in your bedroom to make any difference to the overall levels of oxygen would be ridiculous. Also, these CAM plants, they're not fast growers. It's not like they're a tropical plant that's putting on loads of growth. They're designed to be quite slow. I found that idea quite funny, but it's interesting how people have interpreted this idea of plants opening up their stomata at night and twisted it to their own purposes.

Polly: If you think about it, the atmosphere we breathe is about 20-something% oxygen, so whatever subsidy your Sansevieria provides overnight is going to be a tiny, tiny fraction compared to what's already there in the atmosphere, all the time.

Jane: That's very true. Lovely to have a Sansevieria in your bedroom if you want to, but just don't expect it to be somehow improving the gas in your home.

Polly: It certainly can't hurt.

Jane: No, well, indeed! I'm sure it makes you feel better generally. That's human nature, isn't it? We want to surround ourselves with plants and we come up with all these reasons why we should, other than just "We like them!".

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Jane: Why is it that so many of the plants that use CAM are succulents?

Polly: That's really an interesting thing. So succulent plants, like all plants, have cells that have structures within them called organelles and these are little subcellular places where the cell is doing various jobs and one of the things that plant cells have are these structures called vacuoles and vacuoles are essentially a container of water. In succulents, they have a lot of vacuoles, very large vacuoles full of water that they're storing and that makes them juicy and succulent. The really interesting thing about CAM plants is that overnight, when they're accumulating malic acid, the malic acid is being temporarily stored in those vacuoles. So, the more succulent the plant is the better able it is to accumulate malic acid, so succulent plants tend to almost always be CAM plants. They're really good at accumulating that malic acid and sequestering it overnight so it doesn't interfere with other processes that are going on in the cell.

Jane: That's really interesting. I've always wondered what those vacuoles were up to and now I know!

Polly: Some CAM plants don't have particularly succulent tissues and so their capacity for accumulating malic acid wouldn't be as great as something as super-juicy like a cactus, or something like that. All plants do have vacuoles, so within the CAM plants, they all have some capacity to accumulate malic acid.

Jane: Was Crassulaceae the family they studied, I wonder? Why they called it Crassulacean acid metabolism? I guess they found it in those plants first?

Polly: Yes, in the early-ish 1800s. I can't remember the botanist's name off the top of my head, but for some reason he was tasting a member of the Crassulaceae, I think it was a Bryophyllum and noticed that it got increasingly more acidic-tasting overnight. Why somebody would chew on a Bryophyllum, I have no idea, but that led to the discovery of what was actually happening.

Jane: That's so interesting! I'd love to know what was going through their mind! It's good that they did because it's helped us to understand CAM and that's how great scientific discoveries begin. Don't try this at home folks!

Polly: I don't think it'll hurt you. I've never heard of a member of that family being poisonous, but maybe a few are? It is a neat phenomenon and when I'm teaching, and done field trips where I've taken classes to the desert and I've had students stay up overnight with pH paper and you make a little wound into a cactus and test every hour and you can see measurable changes in pH as the night progresses, and as morning begins it goes from the acidity more to neutrality. It's a really neat phenomenon.

Jane: I'm going to have to get some pH paper and try that out now. My husband's going to be going: "What are you doing, sitting in the dark with your cactus!?"

Polly: Make sure you do it with one that is a little bit stressed in the hot time of summer, so it's not switched over C3, because sometimes if they won't exhibit it, if it's a facultative CAM photosynthesiser.

Jane: We've had a heatwave here, so it might just be the right time to try that out. Is there anything about CAM plants - as anyone who listens to On The Ledge knows, you need to know where your plant comes from to give it the right care - but it doesn't impact on anything in terms of our care other than understanding that succulents don't want to be drowned in humus-rich potting mix all the time. There's no other things that it impacts on in terms of how we care for them, is there?

Polly: I don't think so, especially since a lot of CAM plants are able to do regular photosynthesis if they don't need to be CAM - not all of them, some are more flexible than others. I think mainly it's just making sure that plants don't have soggy roots if they're likely to be CAM plants because they're really not adapted to living in a wet place and having constant moisture. I don't think so. If you just let them dry out in between waterings, they would be fine. They grow slowly but that isn't so much a CAM thing. I'm pretty sure CAM can limit how much plants can grow, to some degree. Their growth is also related to resource limitations in general in the kinds of places they live.

Jane: They're making the best of a not nutrient-rich environment and a very harsh world. It's absolutely astounding when you see Lithops or one of these Mesembs in South Africa. The conditions they're living in, it's absolutely incredible that they can survive, so it's obvious CAM is a really important mechanism for them.

Now we go to the opposite extreme, which is guttation, which is a very different kind of process, exhibited by a different set of plants. People get very alarmed when they see this happening to their plants and they don't know why it's doing it. Where do we start with guttation?

Polly: Guttation is simply happening, usually, overnight. Most plants that aren't CAM, the vast majority of plants on earth, close their stomata at night. So their roots are in the soil and if the soil is moist water is moving from the soil into the roots and it's pushing water up through the roots, through the stems and out into the leaves. It exerts pressure but the stomata are closed, so water isn't going to evaporate out the way it would during the daytime, instead it builds up, builds up, builds up, and it pushes out through these water glands called hydathodes and you get these little tiny water droplets, usually along the margins of leaves or sometimes on little tips or other little locations. I think of it as a relief valve allowing water to escape from the plant because it's moving into the plant just by diffusing from the soil into the roots. There's a continuous column of water being pushed up through the plant and out the leaves. Some people mistake guttation for droplets of dew, but dew is where you have condensation of atmospheric water on tips of leaves or other surfaces where this is actually water coming out of the plant itself.

Jane: Perhaps some people find guttation slightly problematic if water is dripping on soft furnishings. Is there any way of reducing guttation in your plants? Is it better to water in the morning rather than the evening?

Polly: Maybe watering a little bit less? This varies from plant to plant and some plants are going to do it no matter what. It also probably depends on the environment where the plant is living and how humid or not humid it is, because if you have a lot of atmospheric humidity, you're probably going to have more water droplets accumulating and then dropping on the floor on furniture than in an environment where there's low humidity, where it just evaporates. I think if you have a lot of water in the soil then there's a higher likelihood of guttation, but it really varies from plant to plant and some plants don't really do it at all and others do it all the time, or a lot, especially in the mornings. I haven't ever thought about watering at different times, but it might be better to water in the morning, so the plant has the entire day to handle that additional water, rather than watering at night where it's just sitting there overnight and the plant can't take it up and use it, so it can evaporate up the leaves.

Jane: I don't have that many Aroids and I don't have many plants that guttate. I don't know why my plants don't do it. I've got one Epipremnum that is really prone to doing it and it sits on my kitchen windowsill and every time I look at it, it makes me think of the podcast.

Polly: I don't have that many Aroids either, maybe because I live in Southern California where our relative humidity is pretty low a lot of the time. I almost never notice guttation on my houseplants. I've noticed it recently on squash growing in my garden outside. I don't see it happening with my houseplants. I imagine it varies from home environment to home environment a fair amount and, of course, from plant to plant.

Jane: So we have nothing to fear from guttation but it's been fascinating to me, hearing Meet the Listener interviews, to hear that people have really quite strong views about this, which one they prefer, and I'm very interested to hear people's choices and to go: "Oh, okay." I'm always slightly surprised when somebody goes for guttation, but there you go, that's just me and my personal preferences. That's really fascinating to get that insight and hopefully that means that we're all upping our botanical knowledge a little bit further about these two processes. Is there a third option I should introduce to the Meet the Listener option that we haven't talked about?

Polly: Gosh, there's probably always something. One thing about guttation though is something that, I don't know for sure, but I would wonder, if you have a plant that was really rampantly exhibiting guttation, to me, if I had that plant, I might hold back on watering a little bit because I would wonder if there's too much water in the soil and it might be, in the long run, harming the plant. I don't know that, it probably varies a lot from plant to plant in terms of different species.

Jane: I suppose it depends also on whether it's getting watered a lot but it's in a free-draining mix, therefore it's not hanging around. There's so many different factors and it's so dependent on somebody's individual situation. This is where, as we always say on the show, you're observing your plants and what's going on and by understanding these processes and how they're working, hopefully you'll get a sense of whether there's anything really wrong or whether your plant is just happily doing guttation and is quite content with its lot.

Polly: Yes.

Jane: I'm going to have to think if there's anything else we need to add to the Meet the Listener questions, suggestions on an email from listeners please. What other processes have we missed that we should be including? Photosynthesis is, of course, the mother of them all in terms of providing plants with the ability to grow and be there in the first place, but there's so many other cool things going on in leaves that we need to be aware of and that's what's so fun about doing this leaf botany series. There's a few more episodes upcoming where we're going to talk about different things with other experts, but thank you very much for joining me, Polly, it's been really fascinating.

Polly: Thank you for being interested!

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Jane: Thank you so much to Dr Schiffman, aka Polly, for providing all of that great leaf botany information. I know I say this every time but please do click on the show notes link that you'll find in your pod app of choice because there's lots of information on my website to further enhance your knowledge and give you some illustrations of what guttation looks like and so on.

Now the question remains guttation or CAM? Joe from Texas is here to give his answer in this week's Meet the Listener.

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Joe: Hello, I'm Joe. I live in Dallas, Texas and I grew up gardening outside in the arid mountains of Utah and since moving to Dallas, a few years ago, I've been living in apartments, I found that I really missed that connection to nature that you can get by gardening. At that time I really ramped up my indoor plants and currently have around 50 or so. I love Ferns, Palms, Aroids. On The Ledge has really helped me learn so much more about plants. It's really deep in my appreciation for them and especially now I am so grateful to have my small indoor jungle.

Jane: Question one. There's a fire and all your plants are about to burn. Which one do you grab as you escape?

Joe: I would save my Norfolk Pine from the fire. It is such a gorgeous plant with a really unique style. I feel it really adds a lot to the room. I use it as a Christmas Tree. I think a lot of people seem to find this plant really difficult, but as long as it gets enough light and regular watering in a sandy soil, I find it does just fine. The only thing that would be a problem from saving this from the fire, it is so big it would make for a very slow escape.

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

Joe: I loved the Hilton Carter episode. I love learning how he styles the plants, how he gets that really jungly look in the house. I have bought some of his books ever since that episode and I've really been enjoying the process of styling my plants in my home.

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

Joe: Epipremnum pinnatum is my favourite Latin name. I think it's really fun to say! I do like the common name as well, Cebu Blue Pothos. I really like these plants. They're super low maintenance, attractive. I think we could all use more plants like that.

Jane: Question four. Crassulacean acid metabolism or guttation?

Joe: For me, I would definitely take guttation over CAM. Those lovely drops on the leaves just look so beautiful and tell me if I'm keeping it happy. I love seeing them in the morning. It's just a nice thing to wake up to.

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

Joe: I think £200 is a lot of money for a single plant, so the interesting cacti would seem a logical choice. However, I grew up in a desert. I've had more than one run-in with spines on a cactus and I don't feel the need to revisit those experiences! I have always loved jungly tropicals and I think I would go with that Monstera, for sure, plus I do really love a big plant that makes a statement!

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Jane: Thank you, Joe. I hope the rest of Texas forgives you, eventually, for not picking cacti over an Aroid. Only joking, you can pick whatever you like! Thanks very much to Joe and to Polly, my guest this week. I'll be back next Friday. Bye! Right - now where did I leave that pH paper!?

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Jane: The music you heard in this episode was Roll Jordan Roll by The Joy Drops, The Encouragement Stick by Doctor Turtle and Chiefs by Jahzzar. The ad music was by the Heftone Banjo Orchestra, with the tracks Whistling Rufus and Dill Pickles. All tracks are licensed under Creative Commons. Visit my website janeperrone.com for details.

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Regular listeners will know that I’m a tad obsessed with both guttation and CAM (which stands for Crassulacean Acid Metabolism): to the extent that they even feature in the questions I pose listeners who volunteer for an interview! But what exactly are these processes? Dr Polly Schiffman, herself a listener and patron, explains all (and we find out which is her favourite!) Plus I answer a question about a lanky Pilea and we hear from Joe from Texas in Meet the Listener.

Cacti and succulents use CAM to cope with harsh conditions. Photograph: Jane Perrone.

Check out the notes and links below as you listen.

• Following on from last week’s plant ID episode, Australian listener Sonya recommended the app Euclid for identifying Angophora, Corymbia and Eucalyptus.

• If you want to check out my fans’ group on Facebook, it is called Houseplant Fans of On The Ledge.

• My guest this week is Dr Polly Schiffman of California State University, North Ridge in Los Angeles, California in the US. She is a terrestrial ecologist who uses quantitative and experimental approaches to address questions about plants and their ecologies.

• C3 photosynthesis is the ‘regular’ photosynthesis performed by most plants. Here’s a simple guide to how it works.

• CAM or Crassulacean Acid Metabolism is an adaptation of photosynthesis used by certain groups of plants, including cacti and succulents, to cope with living in harsh environments.

• The scientist mentioned by Dr Schiffman who tasted a Bryophyllum was Benjamin Heyne - more on that story here.

• Want to see the sausage-shaped ‘guard cells’ on stomata. Take a look here.

• C4 photosynthesis is explained on Wikipedia.

• Check out a diagram of a plant cell, including a vacuole.

• Guttation is explained in a video here.

• Where does the water come out of the plant? Specialised pores called hydathodes.

Question of the week

Tracy wanted to know how to tame her lanky Pilea peperomioides, aka the Chinese money plant, which had reached 60cm/24in tall and was starting to flop. In the wild, these plants do flop over and grow along the ground when they get tall, so if you want to leave your plant as a ‘hot mess’, that’s fine! If you prefer to tame it, you can chop off any size of cutting from the main stem, which will regrow. Put the cutting in water or in soil with a clear plastic bag over it, and rooting will soon follow.

For more on the Chinese money plant, do check out my episode all about this wonderful houseplant!

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

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THIS WEEK’S SPONSOR

Bite Away®

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I have been recommending the BiteAway to all my friends and family because I’ve been so impressed with how well it works! Bite Away® is dermatologically tested and compact enough to stick in your first aid kit when travelling, or pop in your pocket when you are working in the garden or hiking. It’s suitable for use by allergy sufferers and pregnant women, and you can use it on children safely too.  

Bite Away costs £26.99: buy yours now from Amazon UK. 

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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 Podcasts, Stitcher 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 and Endeavour by Jahzzar. Ad music is  Dill Pickles and Whistling Rufus, both by the Heftone Banjo Orchestra. 

Logo design by Jacqueline Colley.