Episode 269: How plants can save your life
Subscribe to On The Ledge via Spotify, Apple Podcasts, Player FM, Stitcher, Overcast, RadioPublic and YouTube.
TRANSCRIPT
[0:00] Music.
[0:16] Jane Perrone
Welcome to On The Ledge Podcast. I'm your host, Jane Perrone, and in this week's episode, how plants can save your life.
[0:24] Music.
[0:32] Jane Perrone
I'm chatting to Dr. Ross Cameron about the many, many benefits of surrounding yourself with plants this week in the light of his new book, How Plants Can Save Your Life. Plus I answer a question about worms in your plant pots. Thank you very much for joining me and thanks to everyone who gave me delightful feedback about the spider episode last time. It seems like lots of you are giving spiders names - I like to see that and I'm sure Tea will be delighted to hear that too.
[1:08] Thank you also to James AR who gave a lovely review of the podcast. I read that on a day I really needed to hear some good news and it was lovely to hear that On The Ledge is bringing positive benefits to you, James AR. And thank you also to Chelsea who has become a legend after taking up a free trial of the show. An excellent way to dip your toe into the world of Patreon, my crowdfunding platform where you can give me a small amount of cash every month. Find out more in the show notes about the various benefits of Patreon, including ad-free episodes and the Extra Leaf bonus podcast.
[1:50] And very quick bit of housekeeping, I've had a few emails like this recently. If you have pledged for my book Legends of the Leaf and you haven't got your copy, it's probably because you missed the email asking to confirm your postal address because the books won't be sent out until you've confirmed the address you want to send it to. So if you took part in the crowdfunder for my houseplant book, it's called Legends of the Leaf. You can find out more at legendsoftheleafbook.com if you're new to the show. But if you've already pledged and you haven't got your copy, check out your account at unbound.com, log in, and you should be able to check the address that it's going to be sent to. And as soon as you check that and confirm it, it will be sent out to you. Any problems you could drop a line to support@unbound.com or drop me a line. Generally support@unbound.com will be able to help with your queries.
[2:47] Music.
[2:53] Now, I know I rattle on a lot about plants being very good for you, but I also like to back these things up with a bit of science. And that's what this week's interview is all about. Dr. Ross Cameron is Research Director in the Department of Landscape Architecture at the University of Sheffield and he advises the Royal Horticultural Society on matters of environmental horticulture and health and well-being in relation to plants. And his new book, How Plants Can Save Your Life: 50 Inspirational Ideas for Planting and Growing, is a really nice book if you want to look into the science behind all the benefits of plants, and there are many, and get some practical ideas about how you can bring delightful plantiness into your life and improve your physical and mental wellbeing. And in this interview, we cover everything from what phytoncides are, and how they relate to forest bathing, to how you might be being manipulated by your plants. It's mind-blowing stuff. If you want to check out the book I'll put all the details in the show notes and do have a listen. I'm using a new method for my transcripts now which means that the transcripts are available the minute the podcast comes out. So if you want to look at the words as they're being spoken head over to JanePerrone.com now to check out the transcript and the other info there. Right, on with the interview!
[4:27] Great to meet you, Dr Cameron, and we're talking about your new book. This is a book that hopefully gives people a sort of a cornucopia of nice ideas to draw from, plus a bit of the science behind them. I wanted to start off by one of my personal passions, which is something you talk about in the book, the idea of really observing and looking at plants. I would love to know a bit about the science behind this. you talk in the book about attention restoration. Can you tell me a little bit about what that actually means and how we can try to implement a bit of that in our lives?
[5:11] Ross Cameron
Yes, indeed. So attention restoration is one of a number of theories we have as to why plants and nature are beneficial. And it was a term coined by two psychologists back in the 1980s, Stephen and Rachel Kaplan. And it basically works from the idea that normally when we're working hard, when we're concentrating, we have what's called directed attention. You can just imagine sort of honing in on your computer with a problem or a piece of essay or something you're trying to do and the whole brain is working on that. It's very focused. You can sometimes walk away with a bit of a headache because you've been concentrating so hard and the counterbalance to that is indirect attention and that's what nature provides us. It's almost as if you've got a spring in your head and when you go out outdoors again, that spring unwinds, everything relaxes, it de-tenses in some ways. And so nature provides us with this counterbalance, this soft attention, and that has four elements to it for it to work. There is the soft element we call soft fascination, and that's where nature provides us with interesting but not necessarily really absorbing or important features, such as birdsong or seeing a beautiful flower or plant or some sort of insect passing by, things that kind of attract your attention, but they're not fully activating the whole brain. So that's how a fascination is a counterbalance. That's when the spring starts to unwind. And then there are other components, and one is being away from the source of stress. And then the environment itself should be sort of absorbing, it should take you away, that's what we call extent. It doesn't need to be that you have a holiday in the Rocky Mountains, where it should be something that mentally takes you away. And the last one is compatibility, where that environment itself is familiar to you, it's comfortable, it's not challenging in any way.And when those factors come together, that's when you get the most restoration, the most restorative, positive effects.
Jane Perrone
That makes perfect sense. And I like the analogy of the spring. That's very, that's very accurate, I think, for sometimes how I feel. Just before this interview, I went outside and was just giving my tomato seedlings some water. And you know, you immediately have that feeling of when you wander around the garden, immediately things start to just give a release a little bit as you've explained. What are the best ways of achieving that attention restoration then? Is it just any sight of any kind of greenery and nature that we're looking for? I guess it doesn't really matter whether as you say whether it's the Rockies or whether it's the local nettle patch?
Ross Cameron
It's about having, as I say, that place that's slightly comfortable to you and the psychologist would say that's mentally comfortable, not necessarily physically comfortable. So that environment that you feel, you know, that you're not normally stressed. The activities you mentioned, you know, watering the tomatoes, things that are familiar to you, you're kind of tinkering, you're not necessarily having a whole list of tasks to do. And I think using our gardens as that kind of restorative environment around the house is really important. It's either having a wee quiet corner where you can you can sip the coffee and get away from it and watch the birds or you may have a water feature with goldfish or whatever and those are sort of the cues that try and, you know, take us back to the idea of just watching and observing nature. And so it's kind of the environment being passive environment but also being active in terms of relatively non-strenuous, as I say, tinkering-type activities and things like potting on, or pruning, or a bit of light weeding. All these things are just, you know, they're slightly relaxing, they take you away from the main pressure or something that's maybe been bothering you for a while.
Jane Perrone
I think gardeners are their own worst enemy because you speak to people, you know, indoor or outdoor gardeners and say, well, how much time do you spend actually sitting down and enjoying your plants? And they sort of say, well, I never do that. I'm always constantly, you know, battling the next pest or dealing with the latest batch of sowing or cuttings. We tend to kind of almost make too much work for ourselves, I think, sometimes.
Ross Cameron
I think that's right and I think we do actually, even though I would argue that you kind of divide your activity, so you will intentionally go out and do gardening and often at the weekend you'll have a list of must-dos, but I think we also, even though we're not consciously gardening, the fact that we might walk out, you know, take rubbish to the bin or something, you pass flowers, you get that scent of the lavender or whatever, I think there's those unintentional engagements with your plants and environment that probably are doing you some good as well. And we have some evidence of that, that even just having a tub of flowers at the front door, even for people who aren't keen gardeners, does seem to be restorative. It just kind of lifts the spirit.
Jane Perrone
You talked about lavender there, the power of scent. Wow. It really can be quite amazingly intense. The feelings that certain scents can bring on, remind us of childhood or particular of people. How does scent actually affect our brains?
[10:22] Ross Cameron
Yeah, well, I think we've all been there, haven't we? You've just had a whiff of something and you've been in a perfume shop or something like that, or passed, as you say, a rose while walking down the street, and it just seems to act like a time machine momentarily. Almost you can't grasp it. It just jumps in and jumps out again. And I think that's because scent is very evocative of memory. And again, the anatomists will say, well, one of the reasons for that is that the same part of brain, the same part of the brain is working there, what's called the limbic system, so a relatively fundamental part of the brain. And memory and senses are all the signals end up in that part of the brain, as does certain emotions. So often we're using that link between a scent and an emotional response, whether that's some childhood familiarity, you know, the smell of fresh bread or whatever. So there's some sort of primeval link in the brain that kind of brings these three aspects together. So scent is a very old powerful emotion that humans have had.
Jane Perrone
Things like geraniums I find incredibly powerful and also the smell. My mum says this actually because her dad really had lots of allotment greenhouses and the smell of tomatoes in a greenhouse is just absolutely... it's the Proust's madeleine's moment where you're just absolutely transported back to another time.
Ross Cameron
The one that strikes me is the Pelargonium and that's discussed in the book but my very first job in commercial horticulture was was tipping out the flowering shoots and the council's geraniums, the Pelargoniums. And you know you can't now smell them and not go back. It's a very interesting how that one instance links back all the time.
Jane Perrone
You talk about the rose specifically and the ways that we could be being manipulated by the scent of rose. Can you explain what that was all about? Because I found that fascinating.
Ross Cameron
Yeah, I guess this comes from the slightly hard-nosed world of science and biology, but I guess success in biological terms is seen by having almost world domination and having lots of offspring, lots of progeny, that's kind of successful. So you see the David Attenborough documentaries and the species that are doing well are covering the Serengeti etcetera and having lots of young. So in the plant world it's the same sort of assumption that if you're widespread, if you're growing everywhere, you're actually successful evolutionarily speaking. And you can see that from the major crops, you know, about a third of the world is now down to certain grass crops, rice, wheat, etc. So these plants are really successful and we're exploiting them, but arguably evolutionary they're also exploiting us. We're breeding them, we're looking after them, we're nurturing them, or a thousand of them. And from a food perspective, that makes sense. You know, there's definitely a trade-off. We're getting rice and the rice is growing well and dominating, you know, that Asian subcontinent, et cetera. And we're getting the benefits of eating it. But in the case of the rose, it's widely spread, it's grown frequently across different, many different nations. But we're not really getting any benefit except those kind of sensory experiences, the colour, the smell, the sense of romance to some extent. But this is a very successful plant in terms of us cultivating it, looking after it, nurturing it. So there's a play in the book really about who's exploiting who and we do have to realise that these, although they may not have a central nervous system and a brain, but they certainly have a desire to live and succeed. So certain plants are probably doing very well with their symbiotic relationship with us humans and others are not of course.
Jane Perrone
I'm thinking of something like the Venus flytrap for example, which in its native environment is so threatened and is so reduced in its population and yet it's proliferating around the world as something that's often killed but is sold by the million. Probably I'm over-egging the pudding here, but I'm thinking that plant's - its amazing evolutionary path that led it to be able to trap insects has also led it to be able to sort of outrun its own decline.
Ross Cameron
And it's very true. Another good example is Pinus radiata, which is threatened in one little peninsula now in North America, yet it is now the major commercial conifer species for paper and pulp and things like that around the world. So sometimes this little niche that these plants have, it just strikes a chord with, in this case, another species that happens to be us. And that there is a kind of, I mean, exploitation is a slightly strong word, but there's certainly a partnership and that both species are kind of doing well out of it.
[15:17] Jane Perrone
I often think this with a range of species that have been successful as houseplants. They do often have certain characteristics that mean they make very, very successful houseplants, not necessarily mirrored by particularly widespread success in the world, although sometimes they are like the Swiss cheese plant, Monstera deliciosa, which has been naturalized, you know, around the subtropical and tropical world. But it's amazing to me how many houseplants are so very easy to propagate and are very generous. I'm thinking of things like the spider plant, and the Chinese money plant, and to some extent the Tradescantia. And, you know, ferns like the hen and chicken fern that produces lots of babies. There seems to be a link there between the way that they've spread as houseplants and just their amazing ability to reproduce, often vegetatively, without a lot of effort. I don't know if I'm drawing too many conclusions there, but that does seem to be a common thread with houseplants. Maybe they've all got this clever idea of taking over the world via coming into our homes.
[16:24] Ross Cameron
There's almost two strategies, isn't there? because there's the people who are new to horticulture, new to growing plants indoors, and they will like these relatively simple, relatively easy to grow ones, and they will spread and they'll be almost at every second corner shop. You can buy them or you can pick them up at the DIY store. And then there'll be the others that are much more exploiting this sort of exclusivity, this kind of almost plant snobbishness, which are quite difficult to cultivate and there's a challenge. And then people see these as more desirable and will pay through the nose for them. So there's a kind of two-course race going on sometimes I think on the types of plants that are desirable and used. Certainly they're very familiar and easy and then there's also that sort of desire for something that never seems to quite want to grow but will keep making it grow one way or the other.
Jane Perrone
Yeah absolutely and it's a kind of a double-edged sword because by becoming popular as houseplants and you know massively increasing their numbers in captivity as it were, sometimes these plants are then put in terrible danger where they actually grow wild because people are taking them from that environment. So, yeah, there's a lot of plants that fit that category of very desirable but ultimately not that great as houseplants in a lot of scenarios. I'm mainly thinking of the prayer plants, things like, was Calathea now Geoppertia? So many of those sold by the million. You know, as I was saying to a colleague the other week, you don't see many really old Calatheas because very few people can keep that, unless you're in a warm greenhouse, you know, at Wisley, Not many people can get that plant to old age as it were because it's just not that amenable in the normal home environment. Maybe if you live in Florida that would work.
Ross Cameron
I mean I think houseplants themselves are interesting because when you start talking about things like spider plants which we're often propagating from the runners, they're not varying the genetic material. This is a clone as well, so it's not only that one plant is dominating but it may well be that only two or three genetic clones are actually manipulating or dominating the whole of the houseplant world.
[18:38] Jane Perrone
Yeah, that's absolutely right. I mean, when I was writing the book I've written, I discovered that I didn't know before I did the research that the string of pearls, Curio rowleyanus, wasn't really known in the wild and sort of randomly came to a collector in the UK in the 50s and I think has only been found not very frequently in the wild since then. So you think, gosh, have all those many millions of that plant all come from one or two genetic blueprints? I think that might be the case. But it's kind of amazing to think of that being the case. But there you go. That's the wonders of plants that they can reproduce.
Ross Cameron It's quite interesting. It's quite contemporary because we're worried about climate change and whether our plants will adapt or not and of course the ones that were introduced to the horticultural trade were maybe just literally one or two individuals and they won't have that genetic diversity that they might need in future. So there is a sort of desire to go back to the the wild and look at greater variety within a particular species.
[19:45] Music
[19:55] Jane Perrone
More from Dr. Ross Cameron shortly, but now it's time for question of the week. It comes from Jasmin and concerns worms. And Jasmin writes that worm casings slash poo have been turning up in the plastic trays underneath Jasmine's plants. And the cause? Well, Jasmine thinks that they've got there because she mixed some home compost in with potting mix, thinking there'll be some good nutrients in there. And Jasmin's a bit confused because she's read some conflicting information about whether worms are beneficial in house plants or not. Are they eating the plants? What are they doing? Will they affect plant roots? And can she remove them from the plant pot? All great questions. So this can be a problem, particularly if your house plants get moved outside either for temporary watering or for the summer. That way earthworms can make their way into pots. And you probably most of the time won't even know your plants have got earthworms in them. Two things that may happen that give you an indication. One is you see, as Jasmin did, the piles of little piles of soil under the bottom of the pot when when you lift it up, and that's the worm poo where the earthworm has eaten some material and then passed it out the other end, and these tend to come out the bottom of the pot. The other way you might find is if you give the plant a really good dousing with water, the worms might surface at that point, or when you're repotting, obviously.So what are they doing, and are they causing damage? Well, on the whole, earthworms will be eating dead stuff in the soil, so that means organic matter is what they're mainly looking at. But obviously, the volume of soil in a plant pot compared to the soil that worms would be ranging through in the garden is a lot smaller. And so they may start to find that there's not enough organic material for them to work on. And that can mean they move on to feeding on plant roots. If they're in a largeish pot and there's only one or two small ones, they they probably aren't gonna reach that point.And in fact, they might be doing a little bit of good helping to aerate the soil through making passages through the compost, just as you might do physically when you poke a few holes in your house plant compost with a kebab stick or knitting needle as I've recommended before. The worms are doing the job for you. But if you've got a small pot and a worm or two in there, you might find that the roots start to get damaged by the earthworms getting frustrated because they've not got enough to eat.So what can you do about it? If you want to get rid of the worms, the easiest thing to do is to dunk the whole pot, into a big bucket of water. And if you add a drop or two of horticultural soap, that won't harm the plant, but it will mean that the worms really don't want to be in there, then you can keep an eagle eye out and as worms surface and come out of the pot, you can re-home them outside. The other way to do it if you're really worried and don't really like the idea of worms being in the pot is just to un-pot the plant and wash off all the existing substrate and re-pot in new substrate. I think that's probably a bit of an overreaction, but if that's what you need to do, then certainly that is a route through it. The other worms that you might see in your houseplant substrate are potworms. Now these serve pretty much the same function as earthworms, they're eating organic material and pooing it out. They're smaller and thinner than earthworms. They'll probably be less, well about, maybe about a centimetre long or less. And they have sort of white or translucent bodies. And they're quite common in house plant pots as well. Again, same thing applies. You can get rid of them via dousing the pot and adding a bit of horticultural soap. One final type of worm-like creature you might see are fungus gnat larvae. These are visible with the naked eye. They are very small and they're smaller than a pot worm. If you see those, then you need to apply a treatment for fungus gnats and the one I would normally recommend is either BTI or nematodes - and I did a fungus gnat episode very early in the history of the show but I think that's a topic I need to revisit soon because it's a good one. Anyway back to the earthworms, yeah so don't be too alarmed with earthworms in your pots but if you can get rid of them next time you repot, or if you're putting them out for the summer, give the plants a good dunk. And as a preventative measure, before you bring them back indoors, give them a dunk and that way the worms have a chance to get out before you bring them indoors. It's annoying, but generally speaking, most healthy plants won't be adversely affected. The other thing to say is this is only really a problem in plants that are kept continuously moist. So if for example you have a cactus or a succulent outside in the summer and then you bring it indoors and you dry it off more or less for the winter and it's very very dry, the earthworm won't survive anyway because earthworms need moisture to move through the soil and to survive. So really only it's going to apply to pots that are kept moist enough for the earthworms to like the environment and thrive in the environment.
[25:57] I hope that answers your question, Jasmin. And yeah, I think I really should do a fungus gnat episode. So if you've got fungus gnat questions, then do drop me a line and I'll wrap all of that info up into a fungus gnat special. And if you've got any other questions, The email address is the same ontheledgepodcast@gmail.com.
[26:18] If you are always looking for new planty podcasts, I have a recommendation for you today. It's called Our Plant Stories. It's a podcast that digs into the stories that plants tell us about people and places, and the latest episode features, well, me. Here's a trailer from the podcast's producer, Sally Flatman.
Sally Flatman
Our Plant Stories digs into the stories that plants tell us about people and places. So there's always a story. Take the spider plant, a very early plant in Jane Perrone's houseplant career.
Jane Perrone
At the primary school, in the library, there were lots of spider plants. They were chlorotic, they've not been fed or watered in quite some time, and somehow, me and my friend Ruth ended up regularly getting out of class to go and water these spider plants.
Sally Flatman
There's always a conversation with someone who shares the passion for that plant. In this case, a South African botanist.
Jane Perrone
I think they've been in at least four or five different genera over the years until they finally settled in chlorophytum.
Dr Ernst van Jaarsveld
And family as well.
Jane Perrone
Yeah, exactly. They've moved around.
Sally Flatman
And we always learn how to grow it. This time from two women who hold national collections of spider plants.
[27:39] Mercy Morris
The best thing about killing a plant is that you get to do a post-mortem and work out what it is you've done.
Sally Flatman
Our Plant Stories, a new podcast.
Jane Perrone
And now back to my chat with Dr. Ross Cameron. The other thing that really caught my attention in the book, which I kind of knew something about, but I'd love to delve into a little bit here, is, and I never know quite how to pronounce this word, phytoncides. What are they doing in the plant and how are they affecting us when we're exposed to them?
[28:12] Ross Cameron
These are the aromatic chemicals, the citronellas and things like that, that are current in aromatic plants or in some of our conifers and things. So they're quite small organic molecules, they're quite volatile and they usually have some sort of strong sense of smell. And they're there basically to protect the plant from pathogens, from bacteria and fungi, and from animals that are going to eat them. So they make the plant a bit bitter, a bit unpalatable. So they're a defence mechanism as far as the plant's concerned. But the strange irony of it is they seem to be beneficial to us. So we have aromatherapy, we have essential oils, these sort of things which we know were kind of nice smells and relaxers, as we understand the biochemistry better, we're seeing that these molecules are interacting with our body, our physiology, and can elicit or can stimulate our body to have more stronger defence reactions against potentially pathogens. We're also down at the cellular level, so we know that some of these phytoncides will actually activate what are called our killer cells, and these are the cells that will go out and kind of hunt down potential cancer cells and regulate the body's cell production. So it is a fascinating area of biochemistry and the interactions and the key point is that we seem to be really quite strongly linked with these naturally occurring and usually only found in nature in woodlands and things like that, these chemicals and they stimulate the body's defence mechanism.
[29:53] Jane Perrone
So are there particular plants that we can harness, that we should be having around ourselves to maximise our exposure to this?
Ross Cameron
Much of the research is still in its infancy, so most of it has actually come from the Japanese idea of forest bathing, where it was originally just thought to be a relaxation, you just sat in the forest and contemplated life and got away from the stresses and strains as we discussed earlier. And it was only later that a couple of scientists picked up the idea that actually there was chemicals in the forest that seemed to be affecting our physiology and people came away more relaxed. That was because these chemicals were down-regulating things like adrenaline and noradrenaline. There were some lovely tests where basically they extracted the chemicals and used them in different situations and the same positive effects were recorded. So that allowed us to identify that certain aromatic compounds were having certain specific effects on the human body.
[30:52] Jane Perrone
Yeah, I guess there's so much we still don't know about this and how it's affecting our bodies and brains.
Ross Cameron
Yeah, and I think our is a very interesting term because what we're also realising is that we are not really just a human species. We are a walking city of microbial and bacterial and other organisms and only about 40% of our genetic makeup, our cells, are actually Homo sapiens. The rest are, for want of a better word, passengers and symbionts that are on it. So we are much more a biological zoo than we think and that of course then means or explains some of these interactions we have for the natural world.
[31:33] Jane Perrone
Well, that's kind of blown my mind. I did kind of know about the human microbiome, but the way you put that does put things in an interesting perspective, doesn't it? It makes me realise that maybe our understanding of our own biological selves is very much in its infancy, really, let alone our understanding of the world around us.
Ross Cameron
Yeah, and it's a little bit unnerving. I mean, when I first found that fact, I thought, well, a lot of what I'm thinking is being influenced by the environment around me and the microorganisms around me.
Jane Perrone
We should also talk about some of the slightly more down-to-earth aspects of the power of plants to affect us. Now I know that you put together, well you were part of an RHS Chelsea Flower Show exhibit a decade ago or more, which was about green walls and cooling buildings, which is something that's still so current and so probably has come of age as an idea. I mean that was a good, well that was 13 years ago, you were ahead of the curve, what were you doing and where's the current research at in terms of the power of green walls to benefit us and our environment?
Ross Cameron
I think it's worth just going back to why I'm interested in this area. So when I entered horticulture, everybody talked to me about ornamental plants, houseplants, and they were always lovely to look at and that was always understood and that's why they had commercial value etc. But I guess I was interested to see, Is it just the fact they're lovely to look at that we have this desire for them? Or are there other benefits that come other than just the aesthetic? And I got particularly interested in how plants can modify the environment around them. They can raise the humidity of course, but they can also cool the environment and they can cool us. And I felt we weren't using plants enough to modify some of the extremes we had in our city centres or in our houses etc. So the idea of looking at green walls as an environmental benefit, not just an aesthetic, became very much a passion and I was interested to see what types of plants could you grow against a wall, how much did they cool that wall, how much did they keep the wall warm in winter, and did different plants provide different levels of benefits? And I guess I think most of those factors have begun to pan out. Plants do insulate the wall, they'll reduce the air temperature around the wall by about two degrees, but they'll also reduce the surface temperature by as much as sort of maybe even as much 15 to 20 degrees, depending on the weather conditions. And that, some plants are better, significantly better at it than others. And one of the great surprises I found was that of course they do it by two different mechanisms. They do it by shading directly, but they also do it through evapotranspiration. And again, the right plant that's becoming important for the right context and the right problem.
[34:27] Jane Perrone
So, what are the right plants? I guess it depends whether we're talking indoors or outdoors, but are there presumably some plants that are just way better at this than others for this effect?
Ross Cameron
Well, I think they've got different attributes under different situations. I think that's the best way to put it. We still kind of want a combination, a community. If you had a moderately sunny hot day, then something like Lonicera, the honeysuckles, are quite good at keeping your wall cool, keeping the building fabric cooler. When it gets much hotter, more direct midday or something, then something else with shades like ivy provides an extra benefit. So I'm still pushing the idea that actually it's communities of plants and it's a combination of different subtle attributes that actually help provide the maximum benefit. And I guess most people just say, well, a plant cools, doesn't really matter what plant. And I think the exciting thing is, well, it is more subtle and that's more specific and you can get slightly different plants for different situations.
[35:31] Jane Perrone
Yeah, I think that's the key, isn't it? Finding the right plant for the right place. I'm thinking of the office that I'm sitting in outside. There's a Trachelospermum outside on the wall, which is a west-facing wall, and not only I'm training it round the corner to go onto the wall round the corner because I'm thinking the more I can have this building clothed in plants, it's got a green roof on the top as well, the cooler it's going to be on a hot sunny day. Plus, obviously, you get the beautiful scent of the Trachelospermum flowers through the summer, which transports me to an Umbrian hillside or something. You it's a beautiful smell. As you say, it always depresses me when people are so keen to kind of rip plants off walls and assume that they're doing some kind of terrible damage when actually oftentimes they're having a benefit, particularly as we get into the situation where we're facing these hugely high temperatures at times over the summer. That's a real issue and I certainly know with my green roof this room seems to not suffer from quite as much heat and I'm sure that must be because it's got the plants up there which are, shielding me a little bit when it does get really hot. The temperature tends to stay more even in here throughout the summer and winter than the main house which is a traditional tiled roof. I don't have any scientific data to back that up but that's just my anecdote.
Ross Cameron
[36:59] Yeah, I think that there is quite a lot of evidence to back your points up, and not least because you've got the soil and the green roof, the substrate as well, and that holds moisture. But on the point of having plants on the wall, I mean, I think the best scenario is when you've got a little bit of a gap between the plants or something like a rose, which isn't necessarily clinging to the brickwork, it's just kind of rambling up beside it. And you've got some sort of movement of air, a little bit of a buffer zone, as it were, of air between the plant and the wall. That's almost the ideal scenario because you've actually stopped the air movement around the building. You're trapping air but you're not making it stale, there's still some movement. But that means any heat coming off is kind of kept near to the wall or any cooling effect in the summer is kept near to the wall and then the plant is an extra buffer. So it's almost like sort of cavity insulation that having the gaps and the different type of material is actually giving you an overall better benefit than just one layer physically stuck to the wall.
[37:58] Jane Perrone
That's an interesting point. I do remember when I did my RHS course that, you know, the best practice, and I'm not going to say that I've always done this, but the best practice was always to have a gap between the wall and the trellis so that you had sort of a little spacer so that the plant was slightly away from the wall. So that's probably, I'm not sure if I actually did that with my trellis outside. I'd have to go and check. But yeah, that's a really good point. This book obviously has got lots of different ideas and what's nice is that you can kind of dip in and find things that suit your particular situation, you know, whether you've got just house plants or a patio. When you were writing this, was there anything that kind of any particular ideas that you thought, gosh, this is making me want to go and give this a try or any ideas that you particularly love or would recommend people to start with?
Ross Cameron
I think just having that familiarity with plants was the key thing. So obviously I'm doing a lot of the research behind this and one of the drivers for the book was for me was how do I interpret that in practice? How would I advise someday if they wanted one of these beneficial effects? So it's at all different levels and I think the key thing, which we haven't really discussed on, is joy, is what we call positive effect. And so you really want to just, if you're a first time gardener, you really want to start with things that you know you like or you think you might like. And you can almost imagine children in this sort of situation, you know, it is the pansies, it's the nasturtiums, it's the things just growing in pots or in containers just around the door. They sort of start off with stuff that's familiar and easy and gives you those quick rewards. And then with time, I think your tastes take in and there's different styles and you may, want a bubble fountain or something else that particularly attracts you in a certain way. But I think it's making that relationship between your own kind of initial personal interests and then how does that translate out into the world of plants and indeed nature in general?
[40:01]Jane Perrone
That's really true and it's surprising how oftentimes people starting out find that small things give them great anguish. For example, you know, they've got, they've started gardening and they're loving it but they've got a few aphids and then it sort of sends them into a big sort of spiral of despair and I think that's as you grow as a gardener you kind of learn that you've got to take the joy where you can get it and a few aphids shouldn't put you off from that joy. But you're absolutely right. One person's, I don't know, some people might get great joy out of Leylandii, but whatever it is that makes you excited, that's what you got to go for. Even if that sort of puts you out of the current trends, I suppose.
Ross Cameron
Yeah, and I mean, I think attitude's part of that. And as you get older, you get more sort of set in your ways, but the attitude is the key thing in the relationship here. So we really want to avoid the garden being an extra part of the housework. It shouldn't be a chore. And that means different things for people. Some people who are very creative want a lot of colour and will want a lot of different types of activities and different tasks. I'm still a lot of empathy, though, for the person who really just wants to end out with a glass of wine or a cup of tea and just enjoy what's already there. So you have to kind of get into a line with what your own level of interest level engagement is. You can either be very creative and digging up and starting something new every time and really enjoying that, or you can almost just live with what comes in naturally and appreciate that. The aphids no longer become a pest, the aphids just become part of the wildlife.
[41:42] Jane Perrone
If you've just got a big lawn full of dandelions, well there's nothing more joyous than that. And I think the same applies to indoor gardening where again, you don't have to have the trendy the trendy option. You can go for the old-fashioned, supposedly old-fashioned plants and get just as much joy out of them as anything new. And just to finish, we've obviously touched on this that there's lots more that we don't know. Where are you going next or where is our scientists more generally going next with their research into the health benefits of plants?
Ross Cameron
I think there's probably two areas that certainly I'm interested in and the wider team I'm involved with. So I think we already touched on it and not so much on the phytoncides, the microbiomes, this idea that we're picking up beneficial microbial populations and those seem to be the most beneficial ones seem to be close to plants and soil and things like that. So I think there is more about almost cultivating the garden, cultivating soil and then picking up, breathing in literally beneficial organisms. So that's one thing that's in its infancy we need more research on.And the other one I think is a more pragmatic one, is when we start talking about genuinely hospital gardens, hospice gardens, restorative spaces, what sorts of plant combinations are genuinely working well and where's the evidence for that and what's just kind of more anecdotal. So there is a drive to try and think about the type of plant compositions provide a range of different health benefits in those sort of restorative, clinically restorative types of environments. And certainly people like me are challenged for that because there's lots of plants out there and trying to sort of guess what their relative benefits is, well, there's four or five careers in it anyway I think.
[43:35] Jane Perrone
Obviously the garden that won best in show at Chelsea this year was a therapeutic garden for or a spinal unit and the Horatio's garden. And that was fascinating to me hearing about that because it brought together, you know, lots of different elements. So it's no good having a plant that looks amazing but can't be seen by somebody who's lying in a hospital bed, you know, who's actually coming out into the garden, unable to walk or even sit upright. So, you know, there's all these different factors coming in. There must be so much, as you say, so much more work to be done in that area, but what a powerful thing if you can create gardens in hospitals that actually start to have proven benefits for patients. That's definitely got to be worth some more research.
Ross Cameron
I think it's also acknowledging that the road to recovery is actually a number of different chapters. It isn't just the one thing. And whether that's physical health or psychological health, and we know that on that journey, people look for slightly different environments. So if you've just had trauma, you probably actually want, you know, isolation, time on your own, come to terms with it. So that's the green, peaceful places, the quiet places. But after a while you may actually want social interaction, you may want to talk to people about what's happened, etc. And then again, the landscape changes slightly that kind of encourages that and provides opportunity there. So it isn't just a kind of one fix for everything. I think there are different types of environments and landscapes that we can find particular empathy with at those different stages.
[45:12] Jane Perrone
I'll put the details in the show notes for listeners to go and have a look and find out more about this book. There's loads of great ideas in there. So thank you so much for joining me today.
Ross Cameron
It's a pleasure. Thank you.
[45:24] Music.
[45:30] Jane Perrone
Thanks so much to Dr Ross Cameron for that fascinating interview. And do check out the show notes for details of his book How Plants Can Save Your Life, published by Quercus. That's all for this week's show. I'll be back in a couple more weeks with a new episode where I'll be looking at the shady lady tree. Is it the new fiddle leaf fig? We'll find out in the next edition of On The Ledge podcast. But for the moment, have a great fortnight, enjoy your plants and pay attention to them because you never know, they might be paying attention to you. Bye!
[46:10] Music.
[46:33] Jane Perrone
The music you heard in this episode was Roll Jordan Roll by The Joy Drops. The Road We Used to Travel When We Were Kids by Komiku and and Overthrown by Josh Woodward.
Jane Perrone chats to Dr. Ross Cameron about the impact that plants have on our physical and mental health.
This week’s guest
Dr Ross Cameron is research director within the Department of Landscape Architecture at the University of Sheffield and advisor to the Royal Horticultural Society.
His book How Plants Can Save Your Life is out now, published by Quercus.
Patreon subscribers at the Ledge End and Superfan tier can listen to An Extra Leaf 114 where I go deeper into the idea of biophilia with Dr Cameron.
If you want to listen to another planty podcast this week, check out Our Plant Stories by Sally Flatman. You can hear me talking about my early experiences with spider plants in episode 13.
Chapters
0:02:53 Introduction to Dr. Ross Cameron and his new book
0:06:00 How plants can improve mental health
0:10:22 The power of scent
0:12:19 The connection between plants and our health
0:19:55 Q&A: Can worms be beneficial in houseplants?
0:26:19 Interview with Ross Cameron, part two
0:28:12 Phytoncides
0:30:52 Our bodies and brains influenced by microorganisms
0:33:54 How green walls work
0:36:58 Best practices for planting on walls and benefits
0:42:39 Future research on cultivating soil and beneficial organisms
Check out these notes as you listen…
Attention restoration is a theory that explains the how the natural world can provide an antidote to the fatigue and stress of the ‘directed attention’ of office work and other aspects of modern life. Nature provides us with ‘indirect attention’ which provides a counterbalance to this directed attention. It was coined by two psychologists Stephen and Rachel Kaplan in the late 1980s.
Are plants manipulating us? Dr Cameron suggests in his book that some plants that just look good and smell good - such as the rose - may be exploiting us humans to ensure its continued success. The example Dr Cameron gives is Pinus radiata (the Monterey pine) which is threatened in its native habitat yet it is the major conifer species for paper and pul around the world.
Phytoncides are essential oils that can influence human physiology but are used by the plants as defence mechanisms. The Japanese practice of forest bathing works because phtyoncides from the trees were working positively on our bodies.
The human microbiome is the sum of all the microorganisms that live in and on our bodies. This can be affected by our contact with plants and soil, improving our immunity and mental health.
Green walls. Plants growing up walls work in two ways to keep buildings call - by shading walls, but also by evapotranspiration from the leaves.
The Chelsea best in show garden I mention at the end of the interview was designed by Harris Bugg studio and will be resited at a spinal injury unit in Sheffield. More details about Horatio’s Garden here.
QUESTION OF THE WEEK
Jasmin got in touch about a problem with earthworms turning up in her houseplant pots - spotted via the piles of wormcasts (ie poo) that form small piles underneath the pot.
Earthworms can get into houseplant pots if you put them outside for watering or for a summer holiday, or if like Jasmin you use homemade compost as part of the substrate when you repot. They usually don’t cause a lot of damage - their first choice of food is dead organic matter. But if they run out of that, they may start eating plant roots, which can be a problem in small pots. Earthworms are usually only a persistent problem for houseplant soils that are kept constantly moist - for plants where the substrate dries out between waterings, they probably won’t stay alive long.
To get rid of earthworms from houseplant pots, dunk the whole pot in a bucket of water for a few minutes, with a dash of horticultural soap. The worms should try to escape and you can liberate them back outside. You can do this as part of your routine when bringing houseplants inside after the summer to prevent worms from hitching a ride. Alternatively you can remove the pot, wash off the substrate and repot in fresh substrate.
Another type of worm you might find in houseplant soil are potworms which are white or translucent and smaller than earthworms but they serve a very similar purpose in terms of eating dead organic matter. Similar looking but even smaller still are fungus gnat larvae which can be treated with biological controls BTI and nematodes.
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 one extra episode a month, known as An Extra Leaf, as well as ad-free versions of the main podcast 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, The Road We Use To Travel When We Were Kids by Komiku and Overthrown by Josh Woodward.