Episode 120: Begonias part one

Steve Rosenbaum of Texas nursery Steve’s Leaves, in front of a mass of Begonia ‘Fireworks’.

Transcript

Episode 120

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Jane: Hello and welcome to On The Ledge, the podcast that puts the culture back into indoor horticulture. I'm your host, Jane Perrone, and this week we'll begin with the Begonia. Yes, it's the long-awaited Begonia episode. I'm joined by Steve Rosenbaum of Texas nursery, Steve's Leaves, to find out all about these wonderful foliage plants. I'm answering a question about Witch's Fingers, yes, the Sansevieria cylindrica.

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Jane: Many thanks to shoppr1961 and NicoTheFootHillGuru who both left reviews for On The Ledge on Apple Podcast and said very nice things about me, which is always a lovely way to start the day. I also want to send a shout-out to Belsey, who is a new On The Ledge Patreon this week, and to Laura, who gave a one-off donation on ko-fi.com - I don't mention this very often but you can leave a one-off donation if you'd rather not donate monthly. You can do that via the website ko-fi.com Details in my show notes, as always. I'd also urge people to look at the one dollar donation on Patreon, not many people go for this option, yet for $12 a year you could really make a difference in On The Ledge in helping the show to grow. Do take a look at my show notes to find out all those ways to support the show and do keep on leaving those lovely reviews people, it's a brilliant way to help other people find the show and convince them to give it a try.

Thanks for the feedback on the house plant health check episode. One thing that listener Jenny mentioned in the Facebook group, Houseplant Fans of On The Ledge, is that I didn't mention earthworms. She was asking if anyone else was having problems with earth worms and wondering whether they do any harm to plants. The good news, Jenny, is they're not going to harm your plants in the slightest. They don't eat fresh plant material. They'll only eat things that are already rotting. They will, of course, be making worm casts. A tell-tale sign that you have worms is if you get little brown piles of dirt underneath the pot when you lift it up. They're not really going to do any harm. You may be more bothered with them if they're in a terrarium, where you can see them squelching about. Ideally you do want to get them out of the pot because over a long period, they may run out of organic material to work on. The only way you can really do this is by taking the plant out of the pot, putting it on a tarp, and locating those worms and taking them outside to some soil. They will last a long time on a small amount of food but eventually, if they do run out of food, they do pass on, but that's going to take months and months and months. I wouldn't worry about the worms in your terrariums. They're going to be fine until the next time you need to take that terrarium apart - they'll be absolutely fine.

When I was a child I had a massive fish tank aquarium. Because I didn't know any better, I used garden soil and ended up with a lot of worms in there. They were absolutely fine, but as I say, the next time you do a bit of a rejig on that terrarium, you can always remove them then.

The phone is ringing, let me just get this. Yes, I am getting on with the Begonia episode. It's coming very shortly, yes. Steve Rosenbaum. Yes. Okay. Bye! I think it's become clear that you're pretty desperate for some Begonia information, so here goes.

As is often the case, Steve Rosenbaum and I had so much to talk about I'm splitting this interview across two episodes. So coming up in this episode we're discovering the different groups that Begonias fall under, yes it's a very large genus and getting some general care tips for those tricky Rexes and other members of the Begonia clan.

My guest this week, Steve Rosenbaum, has been running Steve's Leaves for many years. He got into terrariums in the 1970s and started his business when he was just 18. He sells thousands of different varieties of tropical plants, including a heck of a lot of lovely Begonias. So he was just the kind of person I needed to talk to, to get some good advice on these plants, which not all of us find that easy. First off, I wanted to find out why he thinks Begonias are undergoing such a renaissance.

Steve: I think there is a general interest in plants. Things are cyclical and this the most interest I've seen since the 1970s. Begonias are, to me, a really fascinating group of plants. It's one of those things that's hard to know why, but they just speak to me when I look at them and I see all the different amazing textures and colours, especially the foliage. The flowers are nice too, but I just think it's such a varied group and that's one of the things that attracts me and they're pretty easy to propagate. I always think that it's good to get people to propagate their plants. I have other people in the industry saying: "You don't want people growing their own plants - then they won't buy as many." Well, you know what, if people get hooked by propagating their plants, they're just going to want more plants and they're going to end up buying more later on, so I'm happy to help people with propagation as well.

Jane: I'm really glad to hear that because I think that's a false idea, that if you teach someone to propagate, then they're never going to buy anything new again. I think it's the exact opposite. As you get deeper in, you can't resist buying more Begonias. As you said, it's quite a big genus. Can we start out by talking about some of the different categories of Begonias that we grow as house plants because there are a few different groupings. How do we divide these up when we're thinking about the different types of Begonias we can grow indoors?

Steve: Some people divide Begonias into eight groups based on their growth habit. The funny thing is there's hybrids between the various groups. They're man-made like any man-made category like that. There are going to be plants that are in between groups. To run through the eight different types of Begonias, there is Cane-like, which a lot of people start with canes and a lot of people are successful with Cane-like Begonias. To me, a similar group are the Shrub-like Begonias, so there are Canes and Shrubs. Then there's Thick-Stemmed Begonias. Some people like those. I don't think they're as common or as popular. Probably the most planted group of begonias are the Semperflorens, and those are sometimes called wax Begonias, or ones used as bedding plants and in mass plantings outside. There are some interesting Semperflorens that can be grown indoors that are collectors' items, but more Semperflorens are just grown as a bedding plant.

Then one of my favourite groups are the Rhizomatous Begonias and then there are the Rex Begonias which are more colourful but a little more challenging and a lot of the Rexes are Rhizomatous - most of them are. Then there's Tuberous. This is the group I have the least experience with and I know there are wonderful growers of Tuberous Begonias in the UK and other places in the world, but we're in Texas and they just don't like the heat, so we steer clear of Tuberous Begonias. Then the final group are the Trailing/Scandent Begonias which are the ones that make great hanging baskets.

Jane: So there's plenty of choice for everybody when it comes to picking a Begonia. As you've said there, one of the groups there, that is the trickiest, are the Rex Begonias, but they're also the ones that people tend to fall for because they're just so gorgeous-looking. If somebody was starting out with Begonias as a house plant, is there any cast iron Begonia that you could recommend, that is the easiest for somebody who doesn't have much experience with this genus?

Steve: I think some of the Cane-like and Shrub-like Begonias are much easier for people. The humidity requirements are a little lower and then also some of the Rhizomatous. There are some cultivars that have been out since the 1800s and species, as well, that were discovered back then, that are easy to grow. As far as to address what you're saying about the Rexees, usually on the Rexes, I find that people send us pictures all the time and they have brown edges and they're not giving them enough humidity. Humidity is the big problem with the Rexes and, of course, you have to give them the proper lighting and watering as well.

Jane: What's the best way of delivering that humidity, because one of the things I'm often arguing with people about, is misting. People think that misting a plant a couple of times a week, that's making a difference to humidity. Does misting help Rex Begonias, or are there better ways of increasing humidity around the plant?

Steve: This is not based on scientific experiments. My personal thought is misting doesn't do much for the plant, but I've known of people who really enjoy misting their plants. It's an activity they do with their plants, so they like doing that. To me, it's more that humans enjoy doing, but I don't think it's going to increase the humidity unless you're going to do it every ten minutes, 24 hours a day, misting once or twice a day is not going to add that much humidity. Some people buy humidifiers. One of my favourites, if you had the location for it and you had one the right size, are terrariums because that raises humidity. Of course, greenhouses are a wonderful way to do it. A lot of the varieties they say can only be grown in a terrarium we find we can grow in the lower humidity. The humidity in the greenhouses is higher than in the home, but it's lower than a terrarium and some of them will make the transition in the greenhouse.

Jane: I suppose the other thing is just putting them in rooms in the house where humidity is likely to be higher, the kitchen or the bathroom maybe, where there's a naturally higher level of humidity.

Steve: Also, some people, their favourite way to do it, this also involves grouping them, is to take a tray of pebbles and add water. The important thing there is not to have the plant sitting in the water, they're sitting on top of the pebbles and the water is only about half-way up and as it evaporates off the pebbles it releases humidity. Then if you group the plants, that helps quite a bit, to me, much more than misting.

Jane: I also wonder when you are misting and putting moisture on to those leaves, whether that's sometimes going to have a detrimental effect if the plant is a little bit cold and it's wet, whether that's encouraging mildew to form as well? I don't know if that's a case of powdery mildew or not related at all, but I know that's another problem that people have with Rexes, is problems with mildew. I don't know if you can shed any light on that?

Steve: Having free water on the leaves can be detrimental. We start all of our plants under a mist system that keeps the foliage damp. So it's not a death sentence because if that was the case every plant under the mist system would die. So you can get the leaves wet but it is a no-no for growing plants. You don't want that free moisture on the leaf, you just want the humidity higher without having the wet leaf if possible. So it can be a problem. Some people would argue it more than I would. I'm just going by my experience.

Jane: If it's a mindfulness activity, misting, then it can be good, but I don't think it's necessarily going to be the ultimate answer for humidity issues. What else is going wrong with begonia Rexes then?

Steve: I was hoping we'd get back to that.

Jane: I need answers! I've killed quite a few of these plants over the years. I've currently got one that is doing okay but sometimes it just seems inexplicable. Suddenly, it'll drop all its leaves and I think: "What's happened? Why am I in this situation yet again?" Are there triggers for plants responding in that way? Dropping all their leaves? Because that seems to be how mine end up going.

Steve: The Rexes are hybrids, except the original Rex and there's not even agreement with scholars on which one is the original Rex, but all the Rexes came from that original plant crossing. At some point it has Rex blood in its history. So they do have a wide variety. So it depends on what they've been crossed with, is where I'm going with that. So when I was a teenager, I grew Rexes in the heat in Texas, they would go dormant. I thought, well, that's just what they do. Some people have them go dormant in cool weather, but I couldn't keep it cool enough, even though I had cooling in my greenhouse at the time when I was a teenager. What I found eventually, was it depended on what they're crossed with. So if they're crossed with a Tuberous or a Semi-tuberous somewhere along the line, then they are going to go dormant in the heat. We have a hybridisation programme. We strive to have Begonias that do not go dormant and that will tolerate the heat. It could be, if it's in the winter time they're going dormant, you may need to give them a little higher temperature. I prefer at the minimum low 60F, that would be about 17C for the low 60s. It's even better if you can do about 20C or upper 60F.

Jane: That's an interesting point. Oftentimes, looking back, my "dead" Rex was actually just dormant and I could have revived it. Is there any way to tell whether a plant, other than just leaving it revive, whether a plant is actually dead or whether it's undergoing dormancy?

Steve: It's pretty easy to tell, there are some Tuberous varieties that will go dormant and they will die back to the Tuber because that's what they do in nature. So those you'd have to dig up or poke your finger down and see if you feel a firm bulb or Tuber down in the soil. But for the Rhizomatous and Rexes, it's very simple. If it has a rhizome on top of the soil, you just squeeze that rhizome gently. If it's nice and firm then the plant is still alive even though there aren't any leaves, if it's mushy or has dried out, then it's a lost cause.

Jane: What's the best way of a plant getting out of dormancy? Is it a waiting game until a new season rolls around? Spring comes and the plant will start to shoot or is there anything you can do to keep it ticking over until that point?

Steve: Well, if we're still talking about Rexes or Rhizomatous Begonias, I would, for one thing, look at the temperature, to see if it is getting too cold. I would try and not let it go dormant, keep it warm enough and if you're having problems because of what it was crossed with, then maybe try some other varieties that are better suited to your growing conditions.

Jane: Is it possible to easily discover what the history of your Rex Begonia is? Is there information out there? Should it be on the label? Or is it a question of searching around for information about its heritage?

Steve: The best way to find out would be, there's an International Begonia Database. It's not perfect but it's the best I know out there. There's a gentleman who is in charge of that named Ross Bolwell, from Australia. He does a wonderful job of trying because he saw a need for having a place where you can look up what the parents are and information about Begonias. That's a great place to go.

I'd like to also mention, besides the humidity with the Rexes, there are also other things. Watering is so critical. The watering and the light are very important. Some people tend to keep plants too wet, some keep them too dry. I usually, from being busy, I tend to keep things too dry. My employees in the greenhouse, they like to keep things a little too wet. I'm always trying to get them to pull back on the watering. Indoors, when you're growing your plants in your home, you do, to me, the best way to do it, is let the soil surface dry and then water thoroughly. Make sure you have draining holes and let some of the water come out of the bottom of the pot. Then that way if you're letting the soil surface, say a half-inch or three-quarters of an inch down, dry, there are a couple of things. One is you'll have fewer fungus gnats because they require constantly moist soil to have fungus gnats and shore flies and annoying pests that live in the top layer of the soil. If that dries out, you're much less likely to have them. But also, some people tell me they keep their Begonias evenly moist and that works for them, but to me, I've always said, it's a slippery slope between constantly moist to thoroughly saturated and too wet. I think it's best to let the soil surface dry than water thoroughly. That way you're not likely to let it keep too wet or let it totally dry out.

Jane: What about the type of water that you're using? I tend to be a bit of a stickler on this and I tend to water almost all of my house plants with rain water because I have a supply of it. Does it make a difference whether you're using water from the tap or rain water or water from some other source?

Steve: It can definitely make a difference, we just use our local city water and it works fine for us. There's nothing all that special about it. It does the job. I know some people will collect rain water, as you mentioned, and some will go as far as using reverse osmosis water to water their plants, if your water quality is bad enough, but rain water is a good choice. It's probably not the water, but if you have a known issue, you can always have your water tested as well, but if you have a known issue, then you may have to go in another direction than just the water that comes out of the faucet.

Jane: Let's talk a little bit about lights, I know you brought that up. Begonias possibly fall into the very large category of house plants that like that strange thing that is bright indirect light, as in no direct sun but lots of light? Am I right there? Are there Begonias that can survive in shadier spots or sunnier spots?

Steve: I agree with what you just said about bright indirect light. Because it's such a broad group, some of them can take quite bright light, some of them can take full sun, especially some of the Semperflorens are grown in full sun, but some of them will take full sun in some types of climates, but not where I'm at in Texas. They'll burn up if you put them in full sun in the summer. So it also depends where you're located because there's not just the light, the temperature plays a role as well, if you get high light and high temperature it can do them in. Bright, indirect, it's hard to quantify, I've heard people try, some people measure it as PAR light or foot candles, but most people don't have meters to check those things. If you have some experience with plants you'll know that plants kind of have built-in light meters in them. If the leaves scorch, then you have too much light on them. I was joking about this yesterday. When you see trails of smoke coming off the leaf, they're probably burning! So they'll scorch in too much light, and if they're getting leggy, spindly, indoors, to me that's a built-in light meter. The growth over time will show you. It's like: "When I first got this plant it was nice and stocky and now it's all leaning towards the window and it looks like it's struggling," and if it's a cane or shrub type and it has an upright stem, there's the nodes, and what they call the inter-nodes. The inter-node areas get too long, that's the plant telling you it needs more light.

Jane: That, I guess, is why it's so important to keep a close eye on your plant when it's something that you treasure and you can react to how it is reacting.

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Jane: Thanks to Steve for joining me this week and I'll be back with Steve next week for more Begonia chat, including answering some of the questions that listeners posed via the Facebook group. Now, it's time for Question of the Week. This one came from Nicki, and she wants to know about Sansevieria cylindrica - the plant known as Witch's Fingers, aka African Spear. She's noticed, when she's taking cuttings of this plant, the new pups grow out as flat plants. Are these then not natural? She's wondering if there's some sort of plastic mould involved, like the fruit that they produce in Japan - those square melons and all that kind of thing. Great question, Nicki, and I can understand why you're confused.

If you can't quite picture this plant, it's a succulent with dapple dark green and pale green leaves that are cylinder-shaped and pointed. So often, because those stems are quite flexible, you'll often find them being sold in a platted form or sometimes you'll find there's just a few of these spears sticking out of the pot. There's all different variations about how this plant is sold. Some people do get quite surprised when they see new leaves coming through and they don't look round, instead they are flat. I do love the idea of lots of tube shaped moulds of Sansevieria cylindrica growing in a nursery, but I'm pleased to say, Nicki, that actually this is a completely natural thing. So, the leaves start off immature as flat. So if you do take a cutting, the leaves that come through will be flat. But gradually, by a form of magic, they gradually become cylindrical as the leaves mature. If you check out the show notes, I'll link to some photos that show immature leaves and the process of how they get to their mature state. It's very common thing for leaves to start out slightly differently than how they end up. It's like a Monstera deliciosa when the leaf first unfurls. It's almost like a butterfly coming out of the chrysalis. It takes a while for it become fully-coloured and to fully pump up and take on its full size. I guess it's a bit like that with the Sansevieria cylindrica leaves. They just take a while to take on their true form.

I guess the other question is why are the leaves like this in the first place? Well, it's an adaptation that many succulents have, to have fleshy leaves to cope with water shortages. I would guess that having a cylindrical leaf reduces the surface area quite considerably compared to a flat leaf, so the plant is losing less water through transpiration. I would guess, this is a complete guess, that means they can cope with more drought than, say, flat leaf Sansevieria, but that's just a theory. I don't actually have any evidence of that. Bear in mind that certain cultivars of Sansevieria won't come true in terms of colour when you make leaf cuttings, they revert to their natural state. So if you've got something like - one of my wishlist plants which I don't yet own. I'm not bitter whatsoever! -Bantel's Sensation. So if you take leaf cuttings of that, rather than divisions, you'll find that they don't look like the parent plant, so that is something to be aware of with these plants. I hope that has helped Nicki. If you've got a question for On The Ledge, you know what to do, drop me a line at and I shall endeavour to help. Photos are always really useful as is tons of information about your plant and what's been happening to it.

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Jane: Well, that rounds up this week's show. I shall be back next Friday with Begonias Part Two. Can't wait! So I shall see you then. Have a great week. Bye!

[music]

Jane: The music you heard in this week's episode was Roll Jordan Roll by The Joy Drops, A Man Approaches with Bowed Sitar, Rishikesh by Samuel Corwin and Enthusiast by Tours. All these tracks are licensed under Creative Commons. Visit JanePerrone.com for details.

Subscribe to On The Ledge via Spotify, Apple Podcasts, Player FM, Stitcher, Overcast, RadioPublic and YouTube.

Begonias are brilliant houseplants: from Rex to luxurians, they come in all kinds of leaf shapes, colours and habits. Steve Rosenbaum, founder of Texas-based nursery Steve’s Leaves, joins me to talk about how to care for these beautiful plants. And I answer a question about the leaves of Sansevieria cylindrica.

Listen to the second instalment of this two-parter on Begonias here!

This week’s guest

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Steve Rosenbaum has been into houseplants since he started growing them as a teenager in the 1970s. He started his nursery Steve’s Leaves as a backyard operation at just 18 and has been going ever since, selling a wide range of Begonias along with other tropical houseplants.

Steve’s Leaves now operates from a four-acre site in Lewisville and Steve and his team is constantly working to keep up with the demand for plants from a new generation of houseplant growers!

Steve and I covered so much ground that I am splitting the episode into two parts - join me next Friday for part two in episode 121!

Begonia notes

1. Begonias are sometimes split into eight different groups based on their growth habit:

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Beefsteak begonia. Photograph: Jane Perrone.

• Canelike

• Shrublike

• Thick stemmed

• Semperflorens (aka wax begonias, usually used as bedding plants)

• Rhizomatous

• Rex

• Tuberous

• Trailing/scandent

2. If you are starting out with Begonias, try one of the canelike or shrublike species, as these tend to be the easiest to grow - they need less humidity and are more tolerant of variable moisture. That said, the easiest Begonia I have ever grown is a rhizomatous type, B. erythrophylla, aka the beefsteak begonia (pictured).

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Begonia ‘Steve’s Leaves Winter Twilight’. Find it on the Steve’s Leaves site here.

3. Lack of humidity is one of the major issues that can be problematic for certain Begonias, especially the Rex types. This often shows up as brown edges on foliage. Steve and I agree that misting doesn’t really help raise humidity around plants unless you do it very frequently; instead, try putting Begonias in terrariums, grouping them together, placing them on a tray of pebbles half-covered with water, putting them in higher-humidity rooms such as bathrooms, or using a humidifier. (Misting leaves may also leave moisture sitting on foliage, which can cause problems, particularly in winter.)

4. Begonias are lovers of that old favourite phrase, ‘bright indirect light’ - that can be hard to judge, but remember that as Steve explains, leaves act as built-in light meters - if they scorch, that’sa sign they are getting too much light. If plants start getting leggy, that means they need more light. It’s often said that B. semperflorens can take full sun, however ‘full sun’ in one climate is not the same as ‘full sun’ in someone else’s - high light combined with high temperatures will kill most begonias.

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Begonia luxurians is a cane-type Begonia. Photograph: Jane Perrone.

5. Begonias can go dormant if conditions are wrong - which can mean too hot or too cold. Tuberous begonias that still have a firm-feeling tuber can usually still be revived, even if they have lost their leaves - likewise rhizomatous species.

6. Temperature-wise, most Begonias like conditions from 17C to around 20C - in Fahrenheit, that’s from the low 60s to the upper 60s. Their exact needs will depend on their heritage - which species they have been crossed with.

7. When it comes to water, allow the surface of the soil to dry out before watering again. If your tap water is hard or contains a lot of chlorine or fluoride, you may be better to use rainwater or reverse osmosis water.

8. If you want to find a Begonia variety, check out the The International Database of the Begoniaceae website, which has a registry of species and cultivars. This will give you a clue as to what conditions it needs.

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Question of the week

Sansevieria cylindrica grows at RHS WIsley in Surrey, England. Photograph: Leonora (Ellie) Enking on Flickr.

Nikky wants to know why her Sansevieria cylindrica cuttings have new leaves that look flat rather than the rounded shape of the rest of the leaves. She’s wondering if the cylindircal leaves are natural, or something man-made?

l do love the idea of lots of tube shaped moulds of Sanseviera cylindrica growing in a nursery, but they are actually completely natural. Weird though it may seem, the leaves start out flat and become cylindrical as they mature. Here’s are some photos that show the immature leaves changing shape over time.

Succulent leaves have evolved to cope with water shortages, so I would guess that having a cylindrical leaf reduces the surface area, so that less moisture is lost to transpiration. I would guess that means they can cope with more drought than other flat-leaved Sansevierias, but that’s just a theory, I don’t have any evidence for it!

As an aside - it’s worth noting thatcertain cultivars will not come ‘true’ when you make leaf cuttings: they’ll revert to their regular colouration, so the only way to propagate one of these is by division - for example my wishlist plant ‘Bantel’s Sensation’ which I still don’t own!

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, A Man Approaches with Bowed Sitar by Samuel Corwin and Enthusiast by Tours.

Logo design by Jacqueline Colley.