Auntie Entity (Begonia rex-cultorum cvv.)

I have a "never again" list, plants that have been so disastrous or unsatisfying for me that I will never buy them again, and Begonia rex is on it.¹

It started with me getting a couple small (three-inch pots) plants as impulse buys from Frontier Garden Center in Cedar Rapids, last September. They were very cheap, and I rationalized at the time that I wouldn't be out much money if they failed to work for me. Which was true enough. The first two were still hanging in there by December, so I got another small one, and then in late December, we got a box of four-inch plants from our main tropicals supplier, which included some real jaw-droppers. (Even WCW was impressed, and she's rarely impressed with anything we get, having reached such a transcendent level of houseplant experience that only the very rarest and weirdest tropical plants can get her excited anymore.) So I chose one called 'Harmony's Red Robin,' with bright red leaves and black centers and edges, and took it home.

Begonia rex-cultorum 'Harmony's Red Robin,' shortly after purchase.
And that worked out for a little while, but then spring hit. I was working more hours at work, and was kind of constantly exhausted from that, and I was even getting a little fed up with taking care of plants all the time. So the watering schedule became a little irregular, the droughts became more frequent and more prolonged, and by February and March, I'd lost the three little ones.

Or, you know, not lost. I still knew where they were. I just wasn't growing them anymore.

'Harmony's Red Robin' (henceforth 'HRR') hung in there for a longer time, but it had going for it that it was a slightly bigger plant, in a slightly bigger pot, and so it was better able to hold on to a little bit of water in its soil than the small ones had been. It still had its problems, though, the main one being that it seemed to have turned into some entirely different cultivar:

Begonia 'Harmony's Red Robin,' quite a while after purchase.
The new leaves were smaller. They still had dark centers and edges, were silver instead of red. The old leaves remained red, and some of them stayed alive for quite some time.

I did play around with giving it different conditions: more light for a while, which didn't do anything noticeable, then I moved it to the bathroom, to give it more humidity, and that didn't change anything either. I eventually decided that it wasn't worth keeping it around just to watch it decline, and got rid of it in late April. Probably an overreaction on my part, but, you know, space is limited. Plants that don't pull their weight can only be permitted for just so long.

So my basic problem was that I couldn't keep the three small ones wet enough. I'm just not that good at plants that have to be kept evenly moist.² But the deal with 'HRR' and the small leaves and all that still has me a little puzzled. Clearly it didn't like something I was doing, but I may never know exactly how and why. It seems like it's either a light or humidity issue, though.

But: we still had the rest of the box from December at work. (They were surprisingly poor sellers, for as colorful as they were. Not sure how to explain that.) They, too, did okay until about March, and then they came down with a bad case of ugly: dark, sunken, round spots in random places on the leaves, due to mildew or possibly a bacterial leaf spot of some kind. Just because they have unreasonably high demands for humidity doesn't mean that they'll accept being touched by actual water, apparently.

Unknown cultivars with leaf spots.
And we had also brought in plugs of two or three varieties of Begonia rex for use as outdoor annuals at this time, which also started to mildew. Things improved a bit when it finally got warm enough that we could move them outside; the mildew (or whatever it was) didn't go away exactly, but the best plants among the survivors were vigorous enough that they could grow faster than the spots could, and kind of outran the spots. The less vigorous plants, on the other hand, drowned in all the rain we got and rotted out faster than you could say, "Hey, you there, stop rotting out."

I understand from WCW that rex begonias as annuals have never worked out all that well for us. I've talked to the boss about not bringing them back for 2009 -- even when they look okay, which is occasional at best, they don't sell all that well, at least not the varieties we had -- and I think she's with me on this. I was only asked for them once by a customer all season, and she wanted a variety we didn't have.³

So. What are rex begonias? Where do they come from? What do they want? Why are they such a pain? And why, oh why did I choose Auntie Entity, a character from the 23-year-old movie Mad Max Beyond Thunderdome, as the "person" to go with this plant? I mean, aside from the fact that Tina Turner is just an all around badass and deserves a plant or two, which should go without saying.⁴


Some of the Begonias from the tropical shipment last December.
Well. Let's start with the reason for tacking on "-cultorum" to the species name. There is a species called Begonia rex, which is native to India. I couldn't find a picture, but the description at this site says that the original Begonia rex was dark, with a silver band. I picture something approximately like 'HRR,' but silver instead of red. It was a rhizomatous species, meaning that its stem (rhizome) crawled along the surface of the ground, producing roots here and there as it went. There were already many rhizomatous species known when the first B. rex was brought to Europe, so the new species was cross-bred with those to yield one new hybrid after another, all differing in leaf shape, size, texture, color, and pattern.⁵ Eventually, such hybrids became their own category, and are collectively referred to as rexes, but since none of them are the actual, original Begonia rex, and since all these varieties contain variable amounts of Begonia rex genes, it's technically more correct to refer to them as B. rex-cultorum, with the "cultorum" part meaning cultivated, and with "cultivated" meaning that we don't know what the fuck it is, really.

Care of Begonia rex-cultorum is described pretty much the same on every website I ran across:

LIGHT: Bright indirect or partial sun (e.g. an east or west window) seems to be preferable, though certain varieties may want more or less than that. One can also grow Begonia rex-cultorum under artificial light fairly easily.

The three small, cheap and doomed Begonia rex-cultorum mentioned earlier in the post.
WATERING: Some growers water from the bottom, like people do for African violets (Saintpaulia ionantha cvv.). I don't think this is a requirement exactly, but it would help keep water off of leaves if mildew has become a problem. Plants should never stand in water for long periods of time, though. Too moist, and they rot. The general recommendation is for water when the soil surface is starting to go dry; this is what did mine in, because I couldn't get to them that often.

TEMPERATURE: Room temperature (68-75ºF / 20-24ºC), or slightly warmer, is what to aim for. There is no consensus on a minimum temperature, but bad things apparently begin to happen around 60ºF (16ºC). (Slightly lower temperatures for short periods may not necessarily kill the plant, though, and the ones at work have been through a few cool nights without obvious damage.)

HUMIDITY: High humidity is non-negotiable, unfortunately. There are a number of ways to achieve this -- misting, pebble trays, terrarium-growing, humidifier -- but any method for raising the humidity level also increases susceptibility to rot. The goal is to maintain high humidity and good air circulation simultaneously. If you're growing in a terrarium, where air circulation isn't really an option, then it's best to be very very clean: the growing medium the plants are in, the tools you use to groom them, the ornaments, if any, you put in the display, etc., all need to be very clean, to avoid introducing disease.

Begonia NOID, possibly 'Merry Christmas.'
PESTS: A couple sites mentioned mealybugs, but the bigger problem is not with insects but with fungus.

GROOMING: Removal of dead leaves is also an important part of good Begonia hygiene, as it can prevent fungus from becoming established in the pot in the first place. Otherwise, there don't seem to be any huge grooming issues: you don't have to prune the plants regularly (though you may want to, if the rhizome has grown over the side of the pot and made the plant look lopsided) or anything like that.

FEEDING: The consensus seems to be that Begonia rex-cultorum needs an ongoing light-strength, balanced fertilizer during the growing season (spring to autumn), which is again a lot like African violets. A 20-20-20, mixed at half (or less) of the directed strength, should be fine.

PROPAGATION: Propagation is the only thing about these guys that's actually easy to do. Though taking stem cuttings will work, the usual method used is leaf-section cuttings, which will produce more plants from a smaller amount of starting material. Take a single leaf from the plant you want to propagate, ideally a leaf which is fully mature but not about to kick the bucket. The first step is optional, and mostly for grower convenience, I think: using sterilized scissors,⁶ cut off the outermost half inch or so of the leaf. Then remove a small circle from around the petiole. You should be left with an arc-shaped piece of leaf. Divide the arc into small wedges, making sure as you do that each wedge contains a major vein: the vein is the point from which the new plants will sprout. The wedges can then be planted into a sterile, moist soilless mix, and then is usually covered with plastic until new plants begin to appear. A different phrasing, which includes pictures, can be found here. I tried sprouting some rex wedges in my mini-greenhouse, and the humidity in there was apparently not high enough (it's not perfectly airtight, on purpose), so that didn't work out,⁷ but I've managed to propagate other begonias⁸ using this method so I know the concept is sound.

A leaf wedge that almost made it. Seriously. This close.
Like with Saintpaulia ionantha, begonia societies exist, though none appear to focus entirely on rexes. It seems to me like there are more than enough varieties of rex-cultorum to keep anybody busy, though. There's decent eye candy at these sites: #1, #2, #3.

Although some varieties are still created using good old-fashioned cross-breeding like grandma used to make, many rex begonias came about as the result of deliberate exposure to mutagenic chemicals or high-energy x-rays.⁹ This process has been used for quite a long time now, to mutate plant genes faster than the plants would do naturally, and is responsible for a surprising number of varieties of agricultural and ornamental plants, including, for example, many of the newer and weirder poinsettia varieties. It's genetic modification, but not quite genetic engineering the way we normally think of it, because with genetic engineering there's usually some actual goal in mind, and specific genes are introduced in the hopes of introducing specific traits. With irradiation, you're basically nuking the plants (or the seeds, or whatever) halfway to hell and then sorting through the rubble to see what's left standing after things stop glowing.¹⁰

Tina Turner, in character as Auntie Entity.
And perhaps now you're seeing the logic behind the choice of "people" here. As the character herself puts it in Mad Max Beyond Thunderdome, describing how she's built up Bartertown into a functional community fifteen years after a nuclear war:¹¹

Do you know who I was? Nobody. Except on the day after, I was still alive. This nobody had a chance to be somebody.

No individual Begonia seed, or leaf, is necessarily all that special either. But survive the irradiation, and you have the chance to be somebody: a named variety of Begonia that can be spread by growers all over the world. Now if one of these radiation-resistant cultivars could just resist rot and mildew too, we'd be all set.

Begonia 'New Merry Christmas,' one of the plants we brought in to sell as annuals.
References and further reading:

Indoor care: Brad's Begonia World
Another blogger's take (from Jan at Always Growing): Always Growing
Deliberate mutation, large-scale production: gpnmag.com
Care info: findarticles.com
More care info (see especially the post by joy4me at the bottom of the page): Garden Web thread
Still more care info: American Begonia Society
Indoor/outdoor transitions, and indoor care: Proven Winners
History, discovery: University of Illinois Extension

-

Photo credits: All my own, except for the Tina Turner picture, which I don't remember where that came from.

¹ Also on the list: Hedera helix, Calathea spp., Kalanchoe luciae or thyrsifolia or whatever it is, Senecio macroglossus, Caladium cvv., Chamaedorea elegans, and Solenostemon scutellarioides. Probable future list members are Radermachera sinica, Echeveria spp., Caryota mitis, Oxalis triangularis, Fenestraria rhopalophylla, Plectrathus ciliatus, and Adenium obesum, though with all of them I still have some hope that maybe things could eventually be worked out.
There is also a "never once" list, which is for plants that so intimidate me that I'm not willing to even try them.
It's possible that although Begonia rex-cultorum is on the "never again" list, I may actually still have some right now: see footnote 8.
² (Don't tell the new Homalomena 'Selby.' Or the Pogonantherum paniceum. Or the Hemigraphis exotica. They're all new, and they don't know. Shhh.)
³ She was looking for 'Escargot,' which we had ordered, but which our supplier substituted something else for. I think the substitute was 'Hurricane Bay.' Which 'Hurricane Bay' is fine, but not what we'd ordered, and it's much less interesting: plainer in color and texture, and without as pronounced of a spiral shape as 'Escargot.'
⁴ (And did, until just now when I said it.)
⁵ The earlier rhizomatous begonias were primarily grown for their flowers, which were showy. Rex-cultorum begonias will flower, but the traits for the impressive flowers have for the most part been bred out of the plant in favor of impressive foliage instead.
⁶ (Scissors wiped with a paper towel that's been wet by rubbing alcohol.)
⁷ Also, I was trying to do this in the middle of winter, using mostly leaves that had broken off of the plants in the box of stuff from Florida and had been sitting in the dark for who knows how long by the time I got them. So there were good reasons for it not to work. Though it was still surprising to me that it was a complete washout.
⁸ At the time, I thought the plant in question was a rex-cultorum. Then, as I was researching this post, I decided that no, probably it wasn't a rex-cultorum, because almost all of them have one base color, a second color along the leaf edge, and a third color at the petiole, and the characteristic lopsided tear-shaped Begonia leaves. This plant has star-shaped leaves and an overall uniform dark red color. And I was happy with that assessment until I saw a picture on this site labeled Begonia 'Coffee Texas Star' that looked a hell of a lot like the plant in question. So now I think maybe it's a rex again.
⁹ One wonders whether the breeders doing this ever refer to them as "rex-rays."
¹⁰ Poetic license. Things do not usually glow after being exposed to radiation. Occasionally things glow while being exposed to radiation, or because they are themselves a source of radiation, but glowing after exposure is mostly a movie-writer shortcut without basis in reality.
¹¹ The original Mad Max and the first sequel did not involve nuclear war, but apparently there'd been a nuclear exchange of some kind between Mad Max 2 and Mad Max 3. I bring it up because I was confused on this point before I started writing this, and figured I probably wasn't the only one who didn't know. Not that it's such an important thing that everybody should have to know.