Episode 194: clear pots - the pros and cons
Transparent pots make root growth easy to observe, and I have found Hoyas do well grown in these containers; such as like Hoya ‘Sunrise’ (left) and Hoya bella. Photograph: Jane Perrone.
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Transcript
Episode 194
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Jane: Hello! Is the microphone on? On The Ledge is back, once I've remembered how everything works! I'm Jane Perrone, the host of podcast On The Ledge, and after a hideously long break I am back with a new episode just for you! How the devil are you? I hope the last few weeks haven't been too hideous without the presence of this here pod. Thanks to all of you who've stayed in touch via social media, dropping me emails and encouraging messages.
Legends of the Leaf, my upcoming book, is chugging along nicely, more of that later, but in this episode I'm going to be taking a look at clear plastic pots. Are they useful? What plants grow in them? What are the pros and cons? I'll also be answering a question about millipedes in a Monstera. Oh yes, I do love a bit of alliteration!
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Jane: Thank you to everybody who has become Patreons of the podcast over the summer period. Hannah became a Crazy Plant Person, Lisa upgraded from Crazy Plant Person to Ledge-end, Alison, Si, Francisca and Jeremy all became Ledge-ends and Lindsay, Lydia, Josh and Mairead became Superfans. Harry and Robin gave one off donations via ko-fi.com, so if you're not looking for a long-term relationship with On The Ledge but just want to pat me on the back for an episode you enjoyed, that is another way of doing it. All the links for one-off donations and Patreon can be found in the show notes at janeperrone.com. One final shout out - the lovely listeners who have been leaving the reviews for the show: Helibear in Germany, MorganOfPearls and Jakaya17 in the US, Ladychetty in the UK. You are all five-star listeners, so thank you very much for adding your kind words about the show and putting them in the public domain.
Right, let's talk about plastic pots and we're going to start off with a little trip inside my house, as much as 10 steps from my office to my main house, and we're going to have a look at some of my plants, planted so you can see the roots. Let's check them out.
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Jane: Now I've come in here, I've actually got to remember which ones are planted in clear plastic! I have to say in my collection the vast majority of those are my Hoyas. Let's have a look at the first one that comes to mind. This is Hoya bella and what am I seeing when I lift up this pot? Well, what's beautiful about the clear plastic pot is it's really easy to see exactly what's going on with the roots of this plant. So, if your plant is in an opaque pot, all you can do is look at the surface and, hopefully, not see roots poking up that way and then look underneath and see some roots coming out the bottom possibly? But when you've got a clear plastic pot there's so much more to be seen. So, looking at this little plant, I've been a bit worried about it because it wasn't getting enough light, so I've moved its location and now I can see how the roots are doing. It's quite a young plant. I got this as a cutting from listener Al - thank you, Al! - and I can see that there's a couple of roots coming out the bottom and I can see roots surging down at the bottom of the pot quite close to the bottom of the pot, so that makes me think that higher up, there's a pretty good root ball forming there, but it's not ready to be repotted. As well as just feeling the weight of the pot I can see how much water is in that soil, from the colour of the soil, and what's happening where the soil is starting to lift away from the edge where it's dry. So the top layer is a paler colour of brown and as I go further down the pot, that colour darkens and you can see that the compost is sitting closer against the edge of the pot because it's damper. There's more moisture there. So while the top is completely dry, if I feel the top of that plant that is absolutely bone dry, down at the bottom I can tell without even sticking my finger in there's a fair degree of moisture down there. So this plant is one that I would look at whether I need to water it or not. Hoya bella is one of the Hoyas that needs more moisture than a lot of the others, so I think in this case I probably will water it, especially given it's still quite actively growing, but it's a great way of telling what's going on with the water. I can also look out for any other issues that might be occurring, whether I've got any beasties in there, we'll be talking about millipedes in potting mixes a bit later on. It just gives me a really good health indicator for this plant and I can say that I'm really happy with how that Hoya is looking.
Let's take up another one that's in a plastic pot. Now this is the other important thing to note here. What I'm doing right now, is I'm popping that clear plastic pot back into a cache pot. We'll talk back in the studio about why I do that, but there are reasons other than just the delightful looks of the cachepot, as opposed to the not-so-delightful look of the clear plastic pot. Okay, who else have we got here in clear plastic?
Another Hoya here. This is a Hoya sunrise cutting that somebody sent me, I'm not sure if they were a listener or not, and I can have a good look at this one. Again, I've got lovely roots. I did post earlier in the week something under the hashtag 'rootporn' because I just love being able to see roots! On this plant, I've got a really good view and I can see that it's rooting nicely, the roots are questing down into the soil. Underneath, I've got one tiny root poking out of the bottom and I can also see that, again, same story with moisture, top half a pot totally dry, bottom half, there's quite a bit of moisture around there. So I'm getting a really good snapshot of what's going on with my plant but I can tell at the top, where the substrate has dried out a bit and it's pulled away from the edge of the pot, that looks very different from the bottom where it's moist. The moisture has made it fluff up and it's pressing against the side of the pot.
One more to look at. This one is another species, but a similar species and a related species, and it's Dischidia and this one has been growing great guns since I got it. I can't remember the Latin name of this one. It might be Ovata. I need to double-check that because I'm terrible at labelling! Again, lifting this one up out of its cache pot, doing beautifully, loads of lovely roots but not ready to repot. It's just so quick to be able to see what's going on with that plant. So that's a little summary of some of the benefits that I find you get from looking at your Hoyas planted this way, as opposed to here, where I've got a Hoya that's in a black pot and I haven't got a scooby-doo what's going on with it! The top of the surface is dry, I'm going to have to stick my finger in there and have a look at what's going on because it's really dry on top but, yes, I can feel that moisture down below but if it was in a clear plastic pot it would be so much easier to see. So that is a little array of some of my Hoyas and their clear plastic pots and let's head back into the studio now to talk about some of the downsides of clear plastic, or potential downsides.
Before I forget, that Dischidia was indeed Dischidia ovata. Well, I think it's called the Watermelon Dischidia, only my second Dischidia after Ruscifolia the Million Hearts, but it seems to be doing really amazingly well. I love Hoyas and Dischidias, as you may well know from listening to the show and it seems a good'un so far.
One thing I didn't mention in that clip was another little thing I do if I'm particularly worried about a plant, and that is get a faithful permanent marker pen, a Sharpie - other permanent marker pens are available - and you can just mark on your pot, on the outside of that transparent pot, where the roots are growing, you can kind of make a root map on the outside. That allows you, in a week or two's time, to then go back to that pot and check whether those roots are growing. It's just a little bit of fun but it can be a useful guide to check whether your plants are expanding their roots, particularly on things like Hoyas where sometimes the top growth can be slow on new cuttings.
So you've seen that most of my clear pots are used for Hoyas and Dischidias. What other plants can you use them for? The most famous group of plants that are often planted in see-through pots are the orchids and that's because orchid roots are covered in a substance called velamen, which can photosynthesise, so that's why orchid roots tend to be a little bit green, especially when you've just watered them. So the idea is your transparent pot lets light through to those roots, they can photosynthesise, the plant is happy, you're happy. As we've said in other episodes about orchids, you don't have to have them planted that way, they can easily grow in opaque pots, but if you want to give them that little extra edge, then a plastic pot can work.
Hoyas and Dischidias, well, they're also epiphytes - that's a plant that grows on another plant - but unlike orchids, they don't have photosynthesising roots but they do have quite small root balls and roots that are potentially used to having a bit more exposure to light than, say, a plant that's planted into the ground. This is worth bearing in mind because roots are programmed to grow down. The hormone, auxin, which is present in roots and in leaves and stems as well, tells them to follow gravity. This is called positive gravitropism, see the word gravity's in there and 'tropism' which means moving. So roots are programmed to grow down and they're also subject to what's called negative phototropism, so that just means they're programmed to grow away from light.
So what happens when you put a plant in a pot with clear plastic? The roots are going to grow away from the light, if you leave that clear plastic pot out on the side without any cachepot around it. Now that could be a positive or a negative. On the one hand, it could potentially stop the plant from becoming root bound, I guess, because those roots would be drawn away from doing the usual thing that roots do which is circling round and round the pot when they run out of room in this substrate. On the other hand, potentially, being sent away from the exterior of the pot might also prevent roots from filling the whole pot, that's the theory. So all I can say on this is use your own experience and experiment with what works for you. I put my transparent pots into a cache pot for two reasons: 1) To save mess and water going everywhere and 2) Because it means that light isn't reaching directly to any roots and that means that I could literally plant any plant that I could think of in a clear plastic pot without worrying. I'm less worried about epiphytes being in a clear plastic pot and light reaching those roots because I think that epiphytes, as I say, they're in the cleft of a tree, the roots are likely to get more light exposure. Another consideration with clear plastic pots, which you can also use for things like growing in Leca and PON -- which, funnily enough, we'll be talking about in an upcoming episode where I interview somebody from the company Lechuza who sells PON about their PON products - one other thing that can happen when you grow in clear plastic is, obviously, that light is passing through into the soil and algae can result. That's another reason to put the clear plastic pot into a cachepot because that will prevent algae from growing. It does happen. If you have a clear plastic pot in sunlight, algae will form on the side of the pot and on the Leca if you are growing it that way. Also, clear plastic pots generate the most heat when it comes to being hit by sunlight. If the plant is in a brown pot or a white pot it tends to reflect more heat back but transparent pots and black pots they hold onto the most heat, which could be an issue for plants that don't like to have hot roots, as it were.
One other aspect of this, I'm not that keen on using plastic and I certainly don't buy any new clear plastic pots myself. My clear plastic pots are ones that I've recycled from plants I've been given orchids in and so on and I will also recycle things, like if my kids come home from the cinema with slushy drinks that come in clear plastic pots, I will repurpose those. You can just stick some holes in the bottom, carefully, with a pair of scissors or a soldering iron. So I never buy plastic because I just think, "Why? The world is absolutely absorbed with plastic. Let's not put any more into the system than we need to" so I tend to try to recycle, recycle, recycle. It's one of the reasons that not all of my plants are planted in clear plastic pots because I've got a lot of existing opaque pots that I still use.
So I'd love to know what you think about clear plastic pots, whether you use them, whether perhaps you're using some other clear pot like glass, the pros and cons you've found and any hitches along the way? I'd love to hear what you think on this subject. Also, this issue of the roots filling the pot. Is it an issue? Should we be concerned about it? Does it work best for certain plants than others? So far, I've only tried this with my epiphyte-type plants and not with anything that would be ground-dwelling like my Aroids. I have heard of people having great success growing Aroids in clear plastic, so let me know what you think. I would love to hear how you're using clear plastic pots.
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Jane: Question of the Week now and it comes from Luke who is 17 from New York and I wanted to answer this question because it just gave me a mental image that was rather arresting, shall I say! Luke has bought a new Monstera deliciosa, that's the Swiss Cheese Plant, from a local big box store - who hasn't done that? - and has brought it home, been very delighted until, on cutting away the plastic container, millipedes started pouring out and Luke writes: "I think I am traumatised for life! One thing I know about millipedes is that once their eggs are laid it's hard to get rid of them. What do you suggest?"
So I'm not sure whether you meant, when you said "the plastic container", Luke, whether you meant the clear plastic sleeve that it was in, or whether you're taking it out of the plastic pot and putting it into another container? Probably the latter. No matter either way. The first thing I'd say was I wonder if you've got millipedes or centipedes? They're both members of the Myriapoda group, so these are both segmented arthropods that tend to exist inside houseplants and in the garden. The way to tell them apart is quite simple. They are different and millipedes, look at each section of their body. Is there one leg on each side, or two legs on each side? Now, millipedes usually have two legs on each of those segments, per side, if you know what I mean. Centipedes - they've got one. So that's a way to tell them apart.
How do you know whether these are good or bad for your houseplants? Basically, centipedes and millipedes do different things, but neither of them is going to pose a threat to your houseplants. Centipedes, they're carnivores, so they will be eating other creatures that might be moving around your plants. They're not going to touch your plant or cause any damage to them. Millipedes, they're detritivores, so that means they're eating rotting matter that exists in the soil and that is not a bad thing either. If they're going to eat a root, it'll only be a dead root, so not so bad. You do get some millipedes that will eat a little bit of live stuff so, possibly, you might have a problem if you have a heck of a lot of millipedes but, generally, they're not something I'd worry about. I guess the main thing is that you just are a little bit freaked out by them, which is a natural reaction, and you may not want to have them in your pot. You're probably not going to see them once you have got your plant has got settled in because they come out at night mainly and it's absolutely fine to just, in any way you can - I always find a dustpan and brush is good for this kind of thing because you can pick them up softly without damaging them but also without having to touch them if you find that problematic - get them outside. That is one way of dealing with them.
If you really can't cope with having them in the pot then what I would suggest is that you need to do a complete repot, where you would shake off all of the substrate from the roots and that will take with it any millipede / centipede presence and, hopefully, their eggs. There is another way to do it, which I like less because it actually kills the millipedes or centipedes and after all we're struggling enough with our invertebrate population so why kill them when they're not doing anything wrong? But if you really want to get rid of them, you can also soak the whole pot in some water with a drop of dish soap or washing up liquid in there and that will drown them. That wouldn't be my preference. I would not recommend it, but if you have a major phobia and you just can't cope with the idea, then that is another way forward, but I would always prefer you to shake off the roots outside. That lets the millipedes or centipedes fly free or, not fly but, you know, crawl free, and then if you really want to be sure, again, you could then put the roots into a tiny bit of soapy water and that would just mean that any eggs that were attached to those roots would then be dealt with.
My main thing would be, also, if you really do suffer from a phobia about insects, is try to get over that because insects are everywhere, invertebrates are everywhere and we need to learn to embrace them because they are so important and we're losing so many of them. So if you do suffer from a genuine phobia of creepy crawlies, as we might say, do go and get some professional help. I know it can be really debilitating and awful to suffer from a phobia like that but there is help out there for you and that way your life gets easier. It's not the quickest thing to solve but there is help out there, so please do go and get help if you have a phobia of creepy crawlies. Luke, I do hope that helps. I'd love to see a picture if you managed to get a picture so we can establish exactly whether you have got a centipede or a millipede, but let me know how you get on and I hope that's helpful.
What do centipedes eat? Well, it's things like spiders and other arthropods, basically, so maybe things that you would quite like them to get rid of for you. If millipedes are living in your houseplant substrate the other thing to consider is whether you can discourage them by reducing the amount of decomposing organic matter in there. If you really have a problem with things like millipedes you could consider moving to a semi-hydro system or a system where you improve the drainage in your soil and that will just probably make it less attractive to millipedes in the first place because it is that rotting material that they're going to be living on.
I hope that's helpful, Luke, and thanks for sending in your question and if you've got a question for On The Ledge drop me a line ontheledgepodcast@gmail.com and I will endeavour to help. If you sent me a question over the summer, I've tried to reply to as many as possible. If I haven't got to you then please do remind me in an email and I'll endeavour to get you an answer.
A quick correction from episode 190 when I answered a question from Lori about aphids on her String of Dolphins and used the wrong Latin name. Thank you to those of you who pointed this out, including Leon, wonderful long-term listener of the show, who sent me a very fascinating scientific paper all about the taxonomic mess, the taxonomic spaghetti, that is the botanical Latin for this plant! String of Dolphins has gone via many and various genera and species names and, indeed, cultivar names and these are usually designated with an x appearing somewhere. So when the x appears before the genus that means it's an inter-generic hybrid, it's a hybrid between species of two different genera. When it appears after the genus name, then it's a hybrid between two different species within the same genus. I shall link in the show notes to a document that explains this, just in case this doesn't quite make sense to you now but maybe a couple of examples will help.
So, have you ever heard of a houseplant called Fatshedera lizei? Well, Fatshedera lizei, is actually x Fatshedera lizei because it's an inter-generic hybrid, also known as a nothogenus, and it's made up of a hybrid between Fatsia and Hedera, ivy and false castor oil plant, but what this paper concludes is that its name should be x Bacurio delphinatifolius. So this is a hybrid between two different species in different genera, Baculellum articulatum and our old friend Curio rowleyanus, the String of Pearls/Beads. So that's where we're at with String of Dolphins taxonomy right now. I'm not sure if that's any clearer!? The name x Bacurio delphinatifolius isn't exactly going to trip off the tongue, but I really appreciate Leon getting in touch to help me with that. If anyone else wants to see a PDF of this paper and really get down deep into the taxonomy, then I shall put a link to it in the show notes. It's from the journal Phytotaxa. I mean, that's my bedtime reading sorted out! You probably think that I'm joking about that, but I'm actually not joking because part of the task of researching the 25 plants I'm profiling for my book, Legends of the Leaf, is looking through an awful lot of academic papers on a wide, wide range of subjects, so I have been spending a lot of time deep in botany. It's great fun though and that is the delight of writing Legends of the Leaf, that I get to give you a deep dive into these plants that you may not have come across in other sources. So, if you haven't pre-ordered your copy, you can do that now - there's a link at janeperrone.com. It should be coming out next year. I'm still writing it, I'm sorry that it's taking as long as it is but, as I say, this isn't something I'm just rushing off, off the top of my noggin! It's requiring a lot of research. So I hope that all the hard work is going to pay off, but if you do want to secure your copy and some of the sweet, sweet merch that you can get with it, then please do check it out if you haven't already.
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Jane: That's all for this week's show, I will be back next Friday. If you're on Twitter at 21:00 BST or 16:00 EDT, do join me for Houseplant Hour, an hour of planty chat and surely the most delightful part of the crazy world of Twitter. Just follow me @houseplanthour or look for the 'houseplanthour' hashtag and you'll find the chat quite easily. If you're a Patreon subscriber, keep an eye on your inbox because I will be releasing the next episode of An Extra Leaf, my bonus podcast, very soon.
I'm going to leave you, if I can, with a quote from garden writer and presenter Thalassa Cruso, who said in her book Making Things Grow: "Enthusiasm wedded to common sense gives everyone a head start in making things grow." Bye!
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Jane: The music you heard in this episode was Roll Jordan Roll by The Joy Drops, The Road We Used To Take When We Were Kids by Komiku and Namaste by Jason Shaw. All tracks are licensed under Creative Commons. Visit the show notes for details.
Clear plastic pots are common in the world of orchid growing, but can they work for other houseplants? I share my experiences growing in transparent pots and delve into a bit of root botany in this episode, plus I answer a question about millipedes in a Monstera.
Check out the notes below as you listen…
Transparent pots are traditionally used for Phalaenopsis and other orchids. That’s because they have a substance on the surface of their roots - velamen - that allows them to photosynthesise.
What about sustainability? I don’t buy new clear plastic pots but try to recycle old ones, and also repurpose clear plastic cups that have been used for other things, eg drinks cups/deli cups. You can add drainage holes in the base with a soldering iron.
One way of keeping an eye on root growth in clear plastic pots is to draw a ‘map’ of the roots with a permanent marker pen so you can chart their growth.
It is far easier to tell when a plant in a clear plastic pot needs watering: dry substrate will look lighter in colour and be pulled away from the side of the pot: wetter substrate will look darker and be pressed against the pot. Usually there will be a gradient from top to bottom, with the driest area at the top.
Roots exhibit positive gravitropism - they grow in the direction of gravity - and negative phototropism - they grow away from light. How does this impact their growth in transparent pots? I am not sure. There are two theories - either it stops the pot getting rootbound by directing the roots away from the pot’s edge, or limits the size of the rootball so not all available soil is used. I’d love your thoughts on this!
Other cons of clear pots? They tend to heat up quicker than light coloured opaque plastic, which can be a problem with plants that like a cool root run, such as ferns. You can counter this by placing clear plastic pots into an opaque outer cachepot to make sure light isn’t reaching roots.
Algae growth can occur in clear pots if they are exposed to light. As above, stick them in a cachepot to prevent this issue.
QUESTION OF THE WEEK
Millipede species Auturus mcclurkini. Photograph: Melissa McMasters on Flickr.
Luke got in touch to ask whether he should be concerned about the mass of millipedes that emerged from his new Monstera deliciosa. (Let’s hope it looked nothing like this.) So, do millipedes pose a threat to houseplants? The comforting answer is, not really. Luke didn’t send a picture but I am wondering if the critters he’s spotted were millipedes or centipedes.
Millipedes and centipedes are both myriapods but aren’t closely related, and there are some key differences. Millipedes have two legs per body segment, whereas centipedes have one. Millipedes are detritivores, eating rotting material such as dead roots, whereas centipedes are carnivores and feed on spiders and other invertebrates. The good news is neither will do major harm to your plants, although some millipedes may have a snack on seedlings and the like. They tend to be nocturnal so you probably won’t see much of them unless you are a night owl.
Why would millipedes be swarming? They may be hatchlings, on the hunt for food or on the hunt for a sexual partner. I suspect Luke’s millipedes have hatched out in the pot and want to go adventuring looking for more food. I’d suggest picking up as many as possible with a dustpan and brush so you can take them outside and release them there. If you really have a phobia of these creatures and need to guarantee they are totally gone, I recommend taking the plant out of its pot, shaking off the potting mix, washing off the roots and repotting in fresh substrate. You could also soak the pot in a bucket of water with a few drops of dish soap/washing up liquid in it, and this would kill the millipedes, and given that we’re currently heading for an ecological Armageddon, this is best avoided if at all possible.
String of dolphins correction
I made an error in the Latin name of the string of dolphins from the listener question in episode 190 - this has now been classified as ×Bacurio delphinatifolius.
xBacurio is a nothogenus - a hybrid of two different genera. String of dolphins is a hybrid between Baculellum articulatum and Curio rowleyanus.
Want to read the string of dolphins taxonomy paper as recommended by Leon? It’s here.
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!
LEGENDS OF THE LEAF
How exciting would it be to get all the wisdom of On The Ledge condensed into a beautiful book?
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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 Namaste by Jason Shaw.