Episode 156: an A to Z of potting mix ingredients, part one
Transcript
Episode 156
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Jane: Hello and welcome to On The Ledge. I'm your host Jane Perrone and this week we're getting down and dirty with potting mixes. If you can't tell your coir from your charcoal, or your leca from your leaf mould, then the next couple of episodes are for you because I'm running through an A - Z of potting mix ingredients and I've got Mr Houseplant, aka Vladan Nikolic, to help me explain the different components that can make up your houseplant potting mixes, plus I'm answering a question about finding houseplant gifts for some very special people.
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Jane: A shout out to this week's new Patreons. Christine and Amy both became Ledge-ends and LisaWTFox and Crystal all became Crazy Plant People and now there's an annual payment, for just over $10 a year, you can show your support for On The Ledge and trust me, every one of those donations is absolutely vital to the show. So, thank you to everyone who has done that. If you're an existing Patreon and you want to swap from monthly to annual payments, you should be able to do that and I've sent you a message on how that's achieved. It's a tiny bit fiddly. If you run into any problems, do give me a shout and I will help you make it work.
JoshuaPD, I've got a bone to pick with you! You left a review for On The Ledge on Apple Podcasts that really gave me a shock. You titled the review: "Awful" and then you gave it five stars! I was first scared and then confused. You start off your review by saying: "This is a terrible podcast. Bad Jane," but then things get better. "I've been buying plants hither and yon" - is that a phrase? I think it's an American phrase. Here in the UK, we say "hither and thither", strangely enough! - "wrecklessly adding to an already way too large plant cacophony". I love the idea of a plant cacophony! "I've had to cast out into the wilderness old plants to make room for the new, hip, happening varieties. Oh, the humanity! It's anarchy." Thank you for giving my heart a little skip there, JoshuaPD, and for your review. I'm glad that I'm introducing you to lots of new plant experiences. Thanks also to PixieGirl84 from the UK, who has left a straightforwardly positive review about On The Ledge, in which they say they're loving my chats with different planty experts on many different aspects of botany. "It made me consider things I hadn't thought about much, such as environmental costs of using certain products and thinking about where our houseplants come from." That's the aim, trying to get those messages across, so thank you very much PixieGirl84 for your review.
I'm always happy to receive constructive criticism and so, this week, I have made a change to the show, as a result of a comment from a listener. This was actually something I was thinking about before this email came in, but it just cemented my decision. It's from somebody who just described themselves as a California listener. I'll read you a little bit of the message: "2020 has proven to become quite the unforgettable year. Being a listener of yours from California, one of your listener questions from the questionnaire has become a lot less fun and more a reality. I often ask myself this question, in the past few months, as I see counties around my home on fire. Which of my 200+ plants would I rescue? None. I have my husband, our son and our two cats. In that time I'd grab that chosen plant, I could spend finding my cats in our burning house, or packing as many essentials as we can stow into our small car. The space that plant would take would be better used for more essentials. Currently, nearly all the states west of the Colorado Rockies are on fire. Climate change is not stopping. It's only gotten worse and worse for California and now many of the western half of the USA. I don't want to be a Negative Nancy. Would it be much to ask you to withdraw 'your house is on fire' question for now because it's becoming a reality for some houseplant lovers, please?" Well, California listener, I hear you completely and I agree that the question has lost a lot of the original intent of being fun and become far too real for too many listeners both in the US and Australia and no doubt in other parts of the world. I'm going to retire that question from now and not use it any more. The new question that's going to replace it, it has the same kind of spirit but it has a completely different slant. I'm not going to tell you quite what it is yet, you'll have to wait for the next Meet the Listener, which won't be happening in this episode, but when it does, I hope that you'll be delighted with the way I've gone with it. It was, I have to say, thanks to my assistant Kelly - I think it was her other half - who came up with the idea for the question. So, I hope that will provide a better way of framing that particular idea of 'What's your favourite plant?'.
I also had an email from Sara on this question. Sara doesn't say where they are, but there are fires burning close to their home. Sara writes: "You always ask the listener what plant they would grab if the house were to catch fire and I thought mine was a Ficus elastica that I propagated from a friend eight years ago and is the oldest remaining plant in my collection. I have a big attachment to it. With wildfires raging everywhere close by, I'm not in an evacuation zone but slowly gathering things near the door just in case. This question has become very real. The answer is that I would not grab my most loved plants, but rather the hardest thing to replace, that is small. If I must leave, I will grab a tiny recent propagate of my beloved tree. It will fit in the car. My giant rubber tree is simply too big. I can always grab a medium, silver Satin Pothos, and a small jar of Brazil Philodendron cuttings if they fit. Almost all my other favourite plants are either super-common or I have a propagate in my office, so I can make more plants. All of this has shown the true value of our ability to propagate our loved plants and therefore have other sources to restart them. Stored with friends, family and co-workers, share the plant love and you'll never be without your favourite for long."
That's an awesome message. I'm loving that, Sara, because that's very true. There are many, many reasons to continuously propagate your plants, but I hadn't thought of that one that. In the event of a catastrophic incident, it is a way that you can pull things back from the brink and in fact, on a very, very much more minor scale I've done that myself recently. I had a Begonia Hatacoa Silver, which is a rather lovely silver splash Begonia which I'd basically killed. I don't know how but I found one tiny, tiny segment of leaf that was still alive - very, very slightly alive. I put it inside my propagation unit which is, basically, just a cake tray with one of those trays that they put muffins in with the clear lid and put it in a little container in there with some moisture and it's grown into a lovely little small plant. On every level, it is worth having propagation going on all the time and giving away those plants, because as you say you never know when you need some cuttings back. This has happened to me. A listener called Lauren, I sent her a Streptocarpus leaf, then I managed to kill the Streptocarpus and she has sent me back a leaf of the plant which I had sent her. What goes around, comes around! Ain't that the truth?
I have an announcement for anyone who is a horticulture professional. I've had a contact from the UCLA Extension, the Horticultural & Gardening programme in California, and they're looking for qualified instructor to teach a new course in indoor plant care. You don't have to be in California to do it because I think it's going to mainly be distance-learning. If you are at all interested in this opportunity, it's a course on identifying houseplants and problems and all of the things we cover in this show. So, if you think you have the right experience and qualifications for this job, I think it's a part-time role, then please do drop a line to ontheledgepodcast@gmail.com and I will drop you back the information that I've had from the programme manager, Melissa McDonald, about the job. Do step forward if you think that might be a great role for you.
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Jane: There is a huge and confusing world of houseplant potting mixes out there. If you've ever stood in the garden centre, staring at brightly coloured bags and not quite sure what to buy, then I'm here to help. I've enlisted another expert to add their tuppence on the matter. My guest this week, Mr Houseplant, aka Vladan Nikolic, is a houseplant care specialist from Washington DC with a huge following on Instagram and he also makes some pretty awesome TikTok videos too. I first came across him via a wonderful TikTok where he was doing a mash-up between computer games and houseplant care, which was absolutely brilliant. I'll put a link to that in the show notes. We're going to be doing some decoding of potting mixes and working out exactly what you need. I guess the first question is, do you need to make your own bespoke potting mixes from individual ingredients, or can you just buy something off the shelf? Here's Mr Houseplant's thoughts on the matter.
Vladan: There are two general types of potting mixes sold out there. You have mixes for tropical plants and mixes for succulent and cacti. With succulent and cacti mixes, yes, a lot of them are good and you could use a lot of them straight out of the bag. However, with tropical mixes, in most cases, for most hobby houseplant growers, they shouldn't use a mix straight out of the bag. The main reason is that most of these commercial mixes are not porous enough.
Jane: Yes, it's all about the holes. Porosity is a really important concept to grasp when it comes to choosing your house plant potting mixes and the truth is not all holes are created equal.
Vladan: In soil, water and air are held in porous spaces in between salt particles. These pores can be different sizes, we can generally classify them as macropores, or large pores, and micropores, or small pores. These macropores, they're often visible to the naked eye, while micropores are not. Macropores are important for good aeration because they hold oxygen, whereas micropores are important for absorbing and holding water. So, it's important to maintain both adequate aeration and water supply for optimal plant growth. It's necessary to have both macro and micro pores in the soil. When I say that most potting mixes aren't porous enough, it means they don't have a lot of these macropores, so they don't provide a lot of oxygen for the roots. In order to have a good soil structure that has both macro and micropores you need a good ratio of small, medium and large particles in the potting mix, you need particles of different sizes. The problem with most commercial mixes is they contain mostly peat moss which consists of very fine particles. So, you have only fine particles, the soil will only contain micropores, which means it will retain water, you won't have a lot of oxygen and it will also compact very easily.
Jane: If you've listened to my sustainability episodes, then hopefully you'll have some awareness of the sustainability issues that surround peat and its use in houseplant compost. It remains a fact that many, many production nurseries still supply their houseplants in potting mixes that contain an extremely high level of peat. So, how come those nurseries can grow plants that look amazingly lush and well but when we get those plants into our homes and don't change the potting mix, they start to struggle. Fortunately, Vlad is on hand to explain that as well.
Vladan: So, does that mean we absolutely cannot use these tropical mixes straight out of the bag? Not necessarily, because even if a mix is not porous enough, when a plant is getting lots of light, it photosynthesises more. As a result, its roots will be pulling more water from the soil. So, what this means is that the roots will not be sitting in wet soil for a long time, so the chances of root rot will be low. This is why plants in nurseries grow in these potting mixes, because nurseries provide huge amounts of light. They have rooves, they have walls made out of glass, they can get 50 times more light than the plants in our homes. So, nurseries need potting mixes that retain a lot of water, which is why they can use these mixes straight out of the bag. The problem with hobby growers is that we don't have this amount of light in our homes and most people, even if they do have a lot of light, they don't provide it to their plants because people usually choose plant placement based on where it will look good not according to how much light it's going to get. So, people often choose a dark corner because it fits well with the interior instead of keeping a plant next to a window. When a plant doesn't get a good amount of light it will photosynthesise less and the roots will be pulling less water from the soil meaning they will be sitting in wet soil longer and increasing the chances of root rot.
Jane: Should you be changing the soil on your new houseplants the minute you get them home from the nursery. This is a subject of enormous debate in various houseplant forums but here's Vlad's take.
Vladan: Plants in nurseries usually go through periods of very intense growth and the soil that they come in could be deficient in nutrients by the time you get them. So, if a plant is nutrient deficient you, of course, want to give it new soil as soon as you can so it can continue developing well. Also, if there is an accumulation of salt in the soil, over time they will burn the roots, so the longer you leave a plant inside that soil, the more damage you will have on the roots. If a plant needs to be repotted, you should repot it as soon as you can.
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Jane: Now, time for Question of the Week, which comes from the Cole family - thank you the Cole family from New South Wales, Australia for getting in touch. Apparently hot summers and cool winters are the order of the day there. The Cole family would like to get their teachers some plants at the end of the year as a present. Great idea! "Our hope is that the teachers will keep a bit of greenery in their classrooms, but to complicate things..." - you sound like me! You like to keep your life as complicated as possible! - " ...we thought it would be really interesting to try to find a plant for each teacher with a name similar to their own. Is that too much to ask?" Okay, so they're trying to match up names. We've got a Suzanne, we've got a Linda, a Nicole, a Kim and an Amy.
For Amy, that one's easy. There is a wonderful Streptocarpus which you can buy from Dibley's in the UK. They've got these amazingly vivid petals which are a mixture of purple and white and the purple venation over white and they're really, really gorgeous. I have no idea if you can get this plant in Australia but if you can, I think Amy is a good option.
There is a new Chinese evergreen Aglaonema called Sapphire Suzanne. It's got pink variegation running down the midrib and into the veins and that's rather lovely if you can get hold of one of those. And, Kim, well, there's a lovely prayer plant, a variegated form of the Rabbit Tracks Maranta Leuconeura and its variety name is Kim, so that would be a good choice. I've also come across a Ficus benjamina cultivar called Nicole, which has got a nice cream and green leaf and is quite compact. Finally, Linda, there's Peperomia rotundifolia with its lovely little heart-shaped leaves, is also known as Yerba Linda. Now, I realise that a lot of those suggestions are a bit out there and I don't know whether you'll be able to get hold of them in New South Wales but I think you could look at this question in a different way and just go by the first letters of the teacher's name.
So, for Suzanne, we could have Suzanne as having a Sansevieria or a Snake Plant. Linda, she could have some Lithops, or possibly a Lipstick Vine, Aeschynanthus. For Nicole, you could get her a Neanthe Bella,which is the old name for Chamaedorea elegans, the Parlour Palm. That may be a little bit obscure unless you're me, but what about a Nepenthes? That would be fun, or even a Norfolk Island pine. Kim, that's easy, Kentia Palm or Kalanchoe, or if she's a Gesneriad fan like me, get her a Koeleria. Amy, well, of course, it's got to be Aspidistra, right? Or maybe an Asparagus Fern, or if you want to give her a challenge, an Alocasia. Those are my ideas, if anyone else has got ideas for the Cole family, then do shout up. Sometimes you just look at a person and you get a sense of what kind of plant they might be interested in, so maybe some background information about these teachers would be useful, or perhaps the subjects that they teach.
That's your starter for ten, Cole family! I hope that's provided you with some inspiration. If any listeners have got their own ideas about what the Cole family should be giving as presents then please let me know. The Cole family sign off by saying: "The Cole family who have just ordered some Coleus seed. See what we did there?" I think your sense of humour and my sense of humour may be fairly similar, guys! Thanks very much for getting in touch. If you've got a question for On The Ledge then shout out and let me know: ontheledgepodcast@gmail.com is the best way to get in touch. If you want to have a look at all those plants named after people that I mentioned, do check out the show notes and they're all listed there.
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Jane: Now, it's time to go deeper into those potting mix ingredients by starting our A - Z. I don't quite have enough ingredients to cover all 26 letters of the alphabet but I've got a fair few covered here. First of all, let's kick off with A. A is for Akadama. What on earth is Akadama? Well, it's a special soil that's mainly used by Bonsai growers. I'm not going to lie, it looks a bit like cat litter but it's a clay-based mineral soil that comes in little tiny balls and it's not that easy to get hold of unless you move in Bonsai circles, though it is becoming more popular as a specialist amendment for houseplant potting mixes, so you may see it coming up in those more specialist houseplant suppliers. The reason why it exists in Japan is this is where it comes from. It's a by-product of volcanic action and you get this very rich clay soil which is really, really porous and holds a lot of water, but it also allows water to drain through it really quickly, which makes it ideal for Bonsai. The complaints against it, well, some Bonsai growers don't use it because they think that it breaks down over time and ends up not being a very good drainage material. I've not used Akadama but I would love to hear from you if it's a regular in your potting mixes and your thoughts on the subject.
Next up, B is for bark. When we think of bark mixes, I think we're probably most often thinking about orchids, which particularly Phalaenopsis are often grown in - just pure chips of bark. What kind of bark is it? Well, it's usually either pine or fir but comes in different grades for different purposes. The very fine stuff, which might only be 0.5cm by 0.5cm, is used very differently from the medium-size bark to the very large chips. I believe there has been a bit of an orchid bark shortage in the UK of late but I tend to buy it from reptile shops. My daughter got her first snake this summer, so I've been in a fair few of those in the last few weeks. In there, you'll find that the same bark that you'd use for your houseplant mix is sold as a substrate for reptiles. So you can pick up the different grades and it may even be cheaper than it is at the garden centre. I like the really fine grade bark for adding to compost mix for things like Ferns and tropical plants. If you've got Phalaenopsis that need repotting, then you'll need much, much larger, either the medium or large grade chips. It's also good for epiphytic plants, such a Hoyas. Obviously they're plants that are growing on branches, so there would be a fair amount of bark in their soil anyway. For these, I tend to either use the fine grade bark, or sometimes if you've got a bag of the large chips, you'll find that there's a load of stuff at the bottom of the bag that collects which is dusty and very, very small pieces of bark, this is ideal for mixing in with your Hoyas'compost.
This is an odd one. B is also for Basic Slag. Yes, you heard that right: Basic Slag. Have you ever come across that term before? I suspect if you are any younger than me, you probably haven't and you probably need to be a little older than me to have come across it. It is a term I came across in a book about epiphyllums that I picked up in a second-hand book shop when I was on holiday. It's called Fine-Flowered Cacti by F R Mcquown. It came out, I think, in the 1960s and this mentioned Basic Slag and I had no idea what he was talking about. I'm just going to find the reference if I can. I think it was a propagation reference. The writer says: "I like to dip each cut surface in Basic Slag." This is a chapter about propagating epiphyllums. So, what on earth is Basic Slag? Apparently it helps the cut to dry cleanly without infection. So, I had to Google this one and it turns out that Basic Slag is a byproduct of making steel. It's got a lot of lime in it and it used to be used as a quite common fertiliser. In fact, I did come across a link to an advert for a grassland fertiliser that was titled: "Basic Slag is back, probably the best grassland fertiliser ever." It seems to be something that has a lot of nutrients for plants in it and that was popular at one point. I guess, if you lived near a steelworks you might be able to get hold of it incredibly cheaply and if you have a big field of crops to fertilise, it might be a very cheap way. I've certainly never come cross it sold in the garden centres, so let me know if you're a Basic Slag user because I'd be interested to hear.
Moving swiftly on. C is for cat litter. I do not own cats but I do usually have some cat litter in my shed. What on earth am I using that for? Well, it's a really, really good substitute for other forms of drainage material such as perlite. Particularly favoured by cactus growers, but you need to get the right kind of cat litter because not all cat litter is created equal. You specifically need to find ones that are non-clumping and usually they'll be described as molar clay or calcined clay. There are a couple of brands that are commonly used in the UK by cactus growers, one of them in Sanicat Pink and the other one is Tesco's low dust cat litter. I'll put links to both of those in the show notes. So, wherever you would use a handful of perlite or a handful of grit in your potting mix, you can just substitute it for a handful of the cat litter. It's perfectly fine to use and it can work out a bit more cheaply than buying something that's actually being marketed as a potting mix ingredient. Hey, if you can pick it up while doing your supermarket shop rather than having to make a special trip to the garden centre, all to the good.
The last ingredient we're going to talk about in this episode is another C; it's C for charcoal, or, more specifically, activated charcoal. You can often pick this up in aquarium shops where it's sold for filters. In the houseplant context, it is a very, very porous substance. The 'activated' bit basically means it goes through a very high temperature process which makes it extremely porous - full of those micropores that Vladan was talking about. That means that it's good at holding nutrients, it's good at holding water, it's good at holding air. It's a very useful thing to add to your potting mix. There are lots of claims bandied about it removing impurities and things, and protecting from bacteria and funguses taking hold. I have to say I take those with a little bit of a pinch of salt. I haven't seen any evidence that it's going to do some incredible purifying work to your soil. I think its main purpose is to add extra porosity to your potting mixes.
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Jane: We will continue with this A - Z next week. We've got lots of other materials to cover. Including diatomaceous earth, rice husks and finding out what on earth, or who on earth, John Innes was and what he had to do with potting mixes! Thanks to Vlad for being my guest this week. He will be back with more insights in the next part of the A - Z. You can find Vlad on Instagram as @nikolicvladan and on Twitter as @mrhouseplant and I'll put all his social links in the show notes.
One final thing to say, if you're the kind of person who likes to be in on the ground floor of something really exciting, you might want to check out my social media channels next Wednesday, around 10am BST. There's going to be a very, very exciting announcement. Don't worry if you can't make that because you'll be hearing about it in next week's show. Oh, the intrigue! Have a legendary week, plant people. I'll see you soon. Bye!
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Jane: The music you heard in this episode was Roll Jordan Roll by The Joy Drops, An Instrument the Boy Called Happy Day, Gokarna by Samuel Corwin and Oh Mallory by Josh Woodward. All tracks are licensed under Creative Commons. Visit janeperrone.com for details.
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I am joined by fellow houseplant expert Mr Houseplant, aka Vladan Nikolic, to discuss the ingredients that go into your plants’ pots, plus I answer a question about finding name-appropriate houseplant gifts.
This week’s guest
Mr Houseplant aka Vladan Nikolic.
Thanks so much to Vlad for joining me to talk all things potting this week! Here’s where you can find out more about Vlad. If you’re looking for the Tiktok I mention, it’s here.
Check out the notes below as you listen. Once the A-Z is complete, I’ll upload a single post containing all the info about every entry!
A is for AKADAMA - a clay-based granular material often used by bonsai enthusiasts. There’s a really detailed description of the pros and cons of this ingredient on the website Bonsai Empire.
B is for BARK - chunks of fir or pine bark, in various sizes from fine to coarse.
B is for BASIC SLAG - I saw this mentioned in vintage Epiphyllum book Fine-Flowered Cacti by FR McQuown, as a substance to dust cuttings. It’s a lime-rich byproduct of steel production that was in the past used as a fertiliser, and still seems to be available although not in your average garden centre.
C is for CAT LITTER - perhaps surprisingly, cat litter is popular in cactus and succulent growingn cirlces as a substitute for grit or perlite. You need to get the right one though - a non-clumping type made from moler or calcined clay. The two brands that seem to be most popular in the Uk for this purpose are Tesco’s low dust cat litter and Sanicat Pink. Here’s how Desert Plants of Avalon uses it.
C is for CHARCOAL - activated charcoal sold as pellets is most cheaply available at aquarium supply shops, where it’s used for filters, but it’s also sold in houseplant shops as horticultural charcoal, such as this Biology Blend from Biochar. In houseplant terms, it can be used as a way of increasing soil porosity.
LEGENDS OF THE LEAF
Question of the week
Here’s a list of the plants I mention as possible gifts for the Cole family’s teachers:
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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CREDITS
This week's show featured the tracks Roll Jordan Roll by the Joy Drops, An Instrument the Boy Called Happy Day, Gokarna by Samuel Corwin and Oh Mallory by Josh Woodward.
Logo design by Jacqueline Colley.