Unfinished business: Strelitzia juncea and Araucaria bidwillii, plus Something Personal-ish

Last September, I got 18 seeds from seedman.com: 5 Strelitzia juncea, 10 Calathea lutea, and 3 Araucaria bidwillii. Including shipping, I paid $16.80.

I knew going in that all three plants are slow and irregular germinators, but even taking that into account, I've been really disappointed. Two Strelitzia seeds came up in October and November, and those look like they're going to be reasonably healthy plants, knock wood. I also have an Araucaria seedling as of January, which appears to have survived being transplanted (did that on 10 April), and is producing new growth as you read this. But I had been expecting a lot more plants than three, and more species than two. If I want to pay $5 for a plant, there are plenty of garden centers around that would accommodate me.

The Strelitzia seedlings as of yesterday.
Also shown: Polyscias fruticosa 'Elegans' (upper right), Euphorbia leuconeura seedling (right center), unidentified Episcia (lower right).
I've purchased several other kinds of seeds from seedman.com,¹ and in most of those cases, I think it was my fault I didn't get any plants. Usually the problem was moisture, either too much or too little (or both). But I feel like I was doing everything right with these seeds, and I'm not getting any better results. So I'm pretty frustrated.

The Araucaria seedling, post-transplant. I was worried for a little bit, but the top third of the stem is all new since the transplant, so it's clearly fine. (Left: Tradescantia pallida; right: Ceropegia woodii.)
I gave up on the Calatheas, and the ungerminated Strelitzias, on Tuesday (20 May); the remaining Araucaria seeds are probably not going to do anything either, but they're in one of the pretzel containers and consequently require no maintenance, so they get a little while longer to try.² This is also probably the last time I buy anything from seedman.com. The service was prompt, as far as I know they sent me the things I asked for, and the prices aren't outrageous, but there's little point in buying the seeds if doing so doesn't eventually result in new plants.

In other news, on Tuesday morning I woke up with what was likely the worst pain I have ever experienced, just to the left of my spine, on my upper back. Well, upper back, shoulder, and neck. That whole area. It turns out that not only is it possible to whimper involuntarily, it's possible to whimper involuntarily without even being fully aware that you're doing it. The pain became, eventually, manageable with ibuprofen. Wednesday was less awful but still pretty bad.

I was worried enough about it to see a doctor late on Wednesday. The best-case scenario I was envisioning was that she'd tell me to just eat lots of ice cream and read my new book about Anthurium breeding,³ and that that would make the pain go away completely, and it would never come back again.

And, well, not quite. The diagnosis was that it was just a pulled trapezius, albeit maybe an especially painfully pulled trapezius. Which I suppose I'm glad that it's nothing serious (The worst case scenario was a slipped/ruptured/herniated disc, which seemed plausible when I was googling on Tuesday night.), and that it will heal. On the other hand, though, if this wasn't something particularly serious, that means that it could happen again. I could wake up shrieking in pain basically any day from now until I die, and there's apparently nothing to be done about it. So, going to sleep at night has just become that much more fraught.

Though I suppose in theory, anybody could wake up in staggering amounts of pain at any time, from one thing or another. The possibility was always there; it just wasn't real to me until this week.

In any case. I did at least get a prescription out of it, because my doctor has a sense of humor. (And because I asked.)

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¹ Pandanus utilis, Cissus rhombifolia, Cordyline fruticosa, Haworthia pumila, Ficus religiosa, Trichocereus peruvianus (possibly Echinopsis?), an Aloe assortment, Carludovica palmata, and a Schefflera of unremembered species (probably S. actinophylla).
² The seeds were still, in theory, capable of germinating, but the more time went by, the less optimistic I was that anything would happen. Also, the more time passed without any sprouts, the more cool things the Anthurium seedlings did, and the less exciting the prospect of having a Calathea lutea seemed when I could up-pot Anthuriums and watch them do cool things.
³ Oh! I have a new book about Anthurium breeding! (Breeding Anthuriums in Hawaii, Haruyuki Kamemoto and Adelheid R. Kuehnle, University of Hawaii Press, Honolulu, 1996, $7.81 used on Amazon and that included shipping) And if you think there are not eventually going to be blog posts about the things I am learning from the book, you are hilariously mistaken.

An Uncharacteristically Upbeat Post

Fungus
Anybody remember that Euphorbia fungus I've been having trouble with since forever? The one that makes the fuzzy white patches on Euphorbia, Pedilanthus, and Synadenium but not on anything else, and that doesn't go away after being sprayed with rubbing alcohol, peroxide, copper sulfate, or chlorothalonil? This stuff?

I think I may have figured out how to get rid of it. The secret might be strong sprays of tap water. Damaged leaves stay damaged, of course, but they don't grow new patches of fungus. I hadn't tried this previously, because usually the equation is fungus + water = more fungus. In fact, I'd been taking extra care not to get water on the affected plants. The only reason I ever tried spraying the plants with water was because I'd gotten so discouraged that I gave up on ever stopping it, so I figured I may as well make it worse so I could justify throwing the plants out.

Rain doesn't work, though: the fungus got worse on the plants that were outside last summer. Must be the chlorine?

The only plants that washing doesn't seem to be adequate for are the Pedilanthuses. Of the three I still have (P. tithymaloides, P. 'Silver Star,' and P. 'Jurassic Park 2'), 'Jurassic Park 2' seems to be cured, 'Silver Star' might or might not be -- it's hard to tell, because there was a lot of leaf damage, and the leaf damage is the same color as the fungus itself -- and P. tithymaloides is still having problems.


Hippeastrum
The Hippeastrum seedling I got three years ago from Kenneth Moore is 1) going to bloom, and 2) offsetting. I'm not sure I even knew that Hippeastrums made offsets before this; I never paid that much attention to the genus because I never thought I was going to have one.

The flower won't be anything terribly exotic; it's either 'Red Lion' x self or 'Red Lion' x 'Apple Blossom.' But it'll still be my first, which is special enough. And amaryllis blooms are pretty, even when they're ordinary.


Clivia
The rumors about Clivia are true. I'd started to think all the talk about Clivia offsets was some kind of elaborate prank aimed at me, to make me feel bad because mine weren't making any. But behold! (And it only took five and a half years!)

So this is a thing that can happen as well.


Araucaria
But the fun doesn't stop there! I also have an Araucaria seedling! (It's less blurry in person.)

Is it an interesting Araucaria seedling? Well no, not yet. But someday. The story is, I bought three seeds of A. bidwillii from seedman.com last September.¹

I started them on 17 September 2013. I got a clear plastic jar (formerly a Costco bulk pretzel container), put in about 2 or 3 inches of damp soil, then set the seeds on top, then added another inch of soil and sealed the top.

In retrospect, I wish I had used vermiculite, because there's a raging fungus gnat problem in the container now. Washing the seeds first might have been a good idea as well, since I've had bugs come in with previous seedman.com purchases. (Only springtails, but if washing might have prevented that, then washing would have been a good idea.) But in any case. They usually take 1-2 months to germinate, but can take up to 18 months to germinate, I've heard, so this may be a long-term dirt-filled pretzel jar.

And here's a bonus picture of my first Araucaria bidwillii, from last September:

In that photo, it's about six and a half years old, plus however old it was when I bought it.²

The advice I see on-line says I should move the seedling to its own pot as soon as it's large enough to be handled.³ I'm not sure how large that is, but the current plan is to give it its own pot once it starts growing some true leaves: currently it's just a short, bumpy stick. If that sounds wrong to anybody, please leave a comment. For that matter, leave a comment if it sounds right, too.


Coffea
Finally, I've seen the first germination from this year's round of Coffea seedlings:

That took a little less than two months to sprout. For this one, I used soil instead of vermiculite, and I didn't soak it in water for 24 hours after harvest, so I hadn't been sure it would do anything. But it seems the pre-drying soak is optional, and it doesn't matter tremendously what you try to germinate them in. For the moment, it's just this one pot, the six seedlings from last year's batch, and the parent plant (which is doing terribly and I don't know why⁴) but I started a pretzel container full of vermiculite and seeds⁵ on January 15, and have two more batches of seeds to sow (95 seeds next week, and 205 seeds in early March), so this is just a harbinger of the coming Coffea stampede.

Bonus picture of the remaining plants from last year's crop:

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¹ $5.95 plus shipping. That was the same order as the Strelitzia junceas (5 seeds for $2.95; previously), and I also got seeds of Calathea lutea (10/$3.95). Both Strelitzia and Calathea are supposed to be irregular germinators, but it may be time to give up on the Calatheas: they take a lot of space that could be going to Anthurium seedlings, and so far none of the ten have done anything. I can be pretty patient when it comes to waiting for plants to do things, so I'm not planning to throw them out immediately, but . . . well, they should start thinking about germinating, if they know what's good for them.
² There is not a lot of information available about how fast A. bidwillii grows once it's germinated, but based on this picture from Wikimedia Commons, I'm guessing mine was barely more than a year old when I bought it. My earliest photo is from October 2007, ten months after the purchase, when it looked like:

Best guess: the plant is now between 7 1/2 and 8 1/2 years old.
³ For example: " As soon as they are large enough to handle, prick the seedlings out into individual pots. The plants have a rather sparse root system and are best placed in their final positions as soon as possible." (From here.) The part about the roots seems correct, at least:

⁴ My best guesses: cold (it's in the plant room, on the floor, and the plant room floor has been very chilly, several times, because of the periodic blasts of cold this winter), dry (it dries out a lot faster than it used to, and probably needs a larger pot), and maybe hot, dry air (the only place big enough to put it is also pretty close to the plant room heater). There's a second plant in the pot, maybe half the size of the big one, and it seems to be doing fine, though, so none of the explanations completely make sense.
⁵ And I do mean full: 149 seeds. The pretzel jars aren't huge -- about 8-10 inches / 20-25 cm in diameter? -- so the seeds are packed in there pretty tightly.

Four Questions for the Hive Mind

Question 1: Is it possible for fuzzy-leaved plants like Episcias to get scale?

I've seen warnings about mealybugs on Episcia, and actual mealybugs on similarly-fuzzy plants, but I don't think I've ever seen anyone talk about scale on Episcia, Saintpaulia, etc. Does it happen? It seems like maybe the hairs would make it hard for them to sit on the stems and leaves like they like to, and I haven't seen any during the whole scale outbreak, is mostly why I'm asking.


Question 2: What was happening here?

The Calathea makoyana had been doing fine for quite a while down in the basement. Then, about a month ago, I had it switch places with an Aglaonema next to it, because the Aglaonema was getting too tall. The Calathea then wound up directly under one of the shop lights. Two weeks later, when I went to water it, the leaves were curled and beginning to wilt, and the undersides of most of the leaves were full of spider mites and sticky spots like this. Thinking "sticky spots = scale," I checked the plant thoroughly, but didn't find any. So I put it back, in its old spot. Two weeks later, I looked at it again, and it looked like the above photo. Still didn't see any actual insects, just spider mites. And unlike the scale on the other side of the basement, the stickiness was only ever on the underside of the leaves, never the top.

The plant was discarded anyway, on the grounds that several of its neighbors had detectable scale infestations, and that was long enough ago that I'm not upset about it now. But I am still wondering how I could have gotten scale without, as far as I can tell, getting scale.


Question 3: How do you keep potted plants upright when outdoors?

I intend to let some of the plants spend the summer outdoors again. The logical place for them to go is along the north side of the garage, which is shaded for most of the day but gets weak sun in the afternoon. Also the husband just poured concrete there, so it's a nice flat surface.

The problem is that the wind comes sweeping in from the west, with basically nothing to block it, and gets funneled between the garage and house, so by the time it reaches the driveway it's moving really fast. Consequently, anything with a high center of gravity gets knocked over every time we have a storm. And we have lots of storms.

Last summer, I had three basic approaches for dealing with this. 1) Put the pots really close together, so even if they catch the wind and want to blow over, they can't. 2) Put bricks on the rim and/or soil. 3) Keep the really top-heavy plants inside. Those kind of worked, but even so, I spent a lot of time righting pots, dashing out into the rain at 4 AM to rush a cart full of plants into the garage, and picking up shards of broken pots.

So I'm hoping that there are better ways that I haven't thought of yet. There is a plantable bed next to this spot, so it might theoretically be possible to plant something cheap or fast-growing to serve as a windbreak (currently, all that's there is grape hyacinth, Muscari something, so there's room), but all we actually have right now are a ton of Cannas and a random bunch of two- or three-year-old seeds.


Question 4: Are there ways to force Agaves to offset? Or even ways to encourage them to offset?

I ask because there was a spell in January when a bunch of Agaves I had all started to offset at once. It could be coincidence, of course, but a couple of the offsetters in January had never even done it before, so it seemed like there was a connection. If I did something to cause it, though, I don't know what that was. Does anybody have any idea how that works?

[Exceptionally] Pretty pictures: transmitted light -- Part XLVI

This isn't maybe the prettiest set of transmitted light photos I've got, but what they lack in beauty, they make up for in having unusually diverse textures. Or at least that was the feature that jumped out at me when I first looked at them as a group.

Ordinarily when I post a set of transmitted light photos, I'm doing so because I can't come up with anything else to post. Not the case this time, though: this time, I'm doing it because I had the realization that if I don't start posting them once in a while, I'm never going to end up publishing them all.

(The previous transmitted light posts can be found here.)

Ficus microcarpa.

Alcea sp. Obviously a leaf from late in the season: a spring leaf wouldn't be as scarred and torn.

Acer sp., autumn.

Pulmonaria 'Raspberry Splash.' One of the two Pulmonarias I planted when we first moved in died this spring; the other had to be relocated and, I fear, may not come back. It needed to be divided, I think, but the husband was the one who moved it, and I hadn't told him it needed to be divided, so . . . we'll see what happens, I suppose. I think I like Pulmonaria well enough to buy replacements if the survivor doesn't come back, but maybe I won't need to. We'll see.

Polyscias scutellaria. The photograph is, I think, a technical failure but an artistic success: the shadows are maybe excessive, but they also make me think of bubble wrap, which I like. (Who doesn't like thinking about bubble wrap, after all?) This is actually, I think, my favorite photo from this set, despite being plainer than most of the images that follow.

Strobilanthes dyerianus.

Epipremnum aureum. It's strangely impossible to come up with a decent transmitted light photo of E. aureum, and I have no idea why. It's like Dracaena deremensis varieties and Tradescantia pallida -- however many different ways I try of doing it, I still always get crappy photos. But what do the three of them have in common that Philodendron hederaceum, Dracaena fragrans, and Tradescantia zebrina don't? It's a mystery.

Glycine max, dead leaf. This improves a bit when full-size. It's also one of the more map-like leaves in this set.

Begonia 'Soli-Mutata.' The texture is pretty striking by reflected light, too, though the colors aren't going to make anybody's list of most colorful Begonias.

Calathea makoyana.

Walkaways Part 16: The Walkawayening, plus one new plant

Just assorted plants that were interesting but left on the shelf. This covers at least a couple months, possibly longer: I had a photo-backlog problem for a lot of the summer and fall.

Acalypha wilkesiana 'Beyond Paradise.'
This would actually have been cheap, unlike almost everything else on the list, but I managed to realize before buying it that I had no spot in the house for a fast-growing plant that needed sun. And, you know, once you have that realization, it takes all the fun out of buying the plant.

Aglaonema NOID.
I don't think I've ever met an Aglaonema I didn't like. (I'm not even sure it's possible.) So this one is on the wish list.

Alocasia 'Loco.'
The variety name wasn't on the plant at the store, but that's what I think it is, based on some internet searching. It's become weirdly common here, all at once -- I'd never seen it before a couple months ago, and then suddenly it was everywhere. I passed it up because, you know, Alocasia = spider mites, and also because I kind of think it's ugly, but it's ugly in an interesting way, at least.

Begonia rex-cultorum NOID (possibly 'Fireworks?').
Never of any serious interest -- I don't intend to buy another rex begonia unless/until I have a dedicated terrarium or greenhouse or something to put them in. And even then, I probably won't bother. But pretty.

Calathea 'Corona.'
Way too big, therefore also way too expensive. Also it's not the best specimen (some burnt margins and scars and stuff, if you look close), and it didn't photograph that well either. But I'm getting dangerously close to buying another Calathea, because I've had my C. makoyana for a year and a half and it hasn't died (probably more a matter of luck than skill). I should probably fight that impulse, though if I found a nice Calathea ornata cheap somewhere, I'd have a hard time resisting.

Hoya NOID.
I don't think I've ever seen a Hoya for sale before that was this loaded with blooms. No ID, though. (Any guesses? UPDATE: Lee, in comments, suggests Hoya nummularioides, which looks like a match from the Google image search results. Thanks!) The flowers were very fragrant, though I didn't entirely like the smell.

Hoya NOID, close-up.
Same plant as above, in the hopes that showing a tighter shot of the flowers would lead to more/better ID guesses.

Kalanchoe tigrina?
Of interest primarily because I've been seeing it forever without knowing what, exactly, it is. I still don't know what it is, but at least I've finally come up with a guess. I would never buy it, because of the aforementioned lighting problems and the fact that about 85% of my experiences with genus Kalanchoe have been bad. Mostly because of lighting. I think.

Monstera adansonii.
I'm not particularly into M. adansonii, but this is an impressively large one.

Neoregelia NOID.
Apparently, this particular variety needs an insane amount of light to maintain its color. This is an old picture, but the plants are still for sale: they've just turned green and are nowhere near as interesting now. This is in the ex-job's greenhouse, which seemed plenty bright when I worked there, so supplying enough light for good color indoors must involve banks of 50 kW lasers or something.

Philodendron bipennifolium.
I had a P. bipennifolium once, and it didn't do well, likely due to inadequate light and humidity. (It didn't actually say what the problem was.) I love the leaf shape, so maybe someday I'll be able to try again.

Not with this particular specimen, though. I didn't check the tag, but I'm sure it must have been like $14,000 or something.

Sansevieria trifasciata 'Bantel's Sensation.'
Didn't need to get this, 'cause I have one (it's been up and down and up again, but it's still alive and producing new growth; currently we're on the upswing), but I was impressed with the size. The only adjustments to this photo were cropping and coloring, but I think it looks more like a real Sansevieria trifasciata when vertically compressed:

Sansevieria trifasciata 'Bantel's Sensation,' 328 x 700 px size. (The above is 328 x 1000 px.)

Schefflera actinophylla NOID.
The last plant I passed up is this yellow Schefflera actinophylla at the ex-job. They told me the cultivar name more than once, but I've forgotten, and I couldn't find it on-line. (I found plenty of names under which people are marketing yellow or chartreuse Schefflera actinophyllas, just not the name they were using for this particular plant. I'm pretty sure I'd recognize it if I saw it again.) I like chartreuse/yellow plants, but again, no money, no room, no light. So I left it.

The one plant I have bought since the last new plants post may be an error in judgment:

Peperomia rugosa.
A lot of the appeal was that I didn't know what it was. The stems looked a lot like those of a cane-type Begonia -- thick, watery, a bit translucent -- and the leaves were wrinkly in the manner of Peperomia caperata but thicker and slightly succulent-feeling, like with some Begonias. There was also a hint of Pilea mixed in there, from the deep grooves running the length of the leaf.

Initially, I assumed that it was probably hard to grow, and declined to buy it on those grounds. Then we went back to the same store a week later, and it looked the same, so I thought maybe this was a recommendation, or at least it was maybe less delicate than I'd originally thought. Also, when I bought it, I was kind of hoping it was an unusually exotic and symmetrical-leaved Begonia, even though I knew that was unlikely.

Of course it wasn't a Begonia. I asked at the UBC Indoor Plants forum, and they told me it was a Peperomia rugosa, which turned out to be correct, damn it. I sort of wish I could take it back, but so far, so good -- after thirteen days, it's only dropped a single leaf, so maybe it has more in common with Peperomias like obtusifolia and clusiifolia (which I do okay with) than with argyreia and caperata (not so much). Time will tell.

Rumble Among the Jungle, Match 5.4

Results of match 4.8:

Considering how enamored y'all have been with Aeoniums in the previous rounds, I was expecting that they'd win again in 4.8, but no -- instead it was Calathea cvv. Just when I think I have you figured out, you go and do something like this. The final score was Aeonium 55, Calathea 70.

The last match from round 5 begins -- now.

Match 5.4
Haworthia spp. vs. Calathea spp./cvv.

Top row, L-R: Haworthia tessellata (?), H. NOID.
Middle row, L-R: Haworthia limifolia var. ubomboensis, H. cymbiformis (?), assortment.
Bottom row, L-R: Haworthia attenuata, H. limifolia var. limifolia.

Clockwise from top left: Calathea ornata, C. roseo-picta 'Medallion' (?), C. makoyana, C. insignis, C. zebrina.

Rumble Among the Jungle, Match 4.8

The result for match 4.4:

4.4 was pretty darn one-sided: Schlumbergera cvv. defeated Hibiscus rosa-sinensis 75 to 39.

I mention this because large margins of victory were fairly regular occurrences during the first couple rounds, but the last time we saw anything like a 66%-34% split was back in match 3.7. That one was also a win for Schlumbergera (over Platycerium spp.), so perhaps we should be keeping an eye on Schlumbergera to win the whole tournament. Perhaps not. I don't know.

In any case, here's the last match for round 4:

Match 4.8
Aeonium spp. vs. Calathea spp./cvv.

Clockwise from top: Aeonium 'Kiwi,' 'Irish Bouquet,' A. arboreum atropurpureum 'Zwartkop.'

Clockwise from top left: Calathea ornata, C. roseo-picta 'Medallion' (?), C. makoyana, C. insignis, C. zebrina.

List: Green-Leaved Plants With Red or Purple Undersides

I could have sworn that I'd read that leaves with red or purple undersides are an adaptation by understory-dwelling plants to collect more light. Damned if I can find a source to back me up, though: Google failed me completely. I checked some of my books, too. So maybe that's not true. Most of these do appear to be understory plants, though, whatever the reason for their pigmentation.

Alpinia luteocarpa (bamboo ginger)¹.

Calathea roseopicta 'Medallion.' I think.

Cissus discolor (begonia vine).

Cyanotis kewensis (teddy bear plant).

Excoecaria cochinchinensis (Chinese croton).

Hemigraphis exotica (purple waffle plant).

Nematanthus NOID (guppy plant).

Philodendron hederaceum micans (heart-leaf philodendron).

Selaginella erythropus cv. (red spike moss)

Tradescantia spathacea. (oyster plant, Moses in the cradle)

Making recommendations from this batch of plants is pretty easy, since there are only four plants on the list that I've had good experiences with (Cyanotis, Nematanthus, Philodendron, Tradescantia).

Of those four, Philodendron hederaceum micans is far and away the easiest; it's an adaptable, flexible plant that will survive a fair amount of abuse while still looking good. Tradescantia spathacea is next: it's a perfectly nice plant, and also very tolerant, but it won't develop the purple coloration without a lot of light, so it is demanding on that one point.

Cyanotis kewensis and Nematanthus cvv. are both a little fussy for me: both are usually robust and fast-growing, but both also sometimes die back for no obvious reason, and Nematanthus sometimes abruptly defoliates, which is likely either a cry for more light or a delayed response to drought. Both also need fairly bright light, and not all Nematanthus varieties have the red underside. So those are tied for my third recommendation.

The rest of this field is not very promising.

I've never tried Alpinia luteocarpa, but the ginger family plants I am acquainted with aren't plants I'd necessarily recommend to anybody.²

Calatheas are virtually never a good idea, for anybody, though they're not the worst choice from the list.

I've heard of people keeping a Cissus discolor indoors for any substantial length of time, but I think the people telling those stories are lying.

Excoecaria cochinchinensis and I only just met, so I have no idea what it's like.

I've tried Hemigraphis exotica twice now and will not be buying a third one; they need very intense light to maintain their coloration, plus they can't go dry, even briefly. Since briefly going dry is something that's very likely to happen to a plant that's in intense light, this basically means that you really have to be on the ball with the watering.

And, finally, Selaginella erythropus, which may be the very worst choice possible from this list, unless you plan to put it in a terrarium. In a terrarium, it'll probably do great.

Not pictured:

• Several Alocasias have green or gray surfaces with purple undersides, including A. amazonica 'Polly,' A. 'Mayan Mask,' and A. lauterbachiana. They're a bit too attractive to spider mites for my tastes, and 'Mayan Mask' is huge, but it is possible to grow them indoors. (suggested by tay696)
• Many Begonia cvv. have red undersides; B. x erythrophylla, the "beefsteak begonia," has a particularly vivid green-red contrast and is easy to grow.
• Virtually all Calathea varieties have red or purple undersides: C. burle-marxii, C. insignis (rattlesnake plant), C. makoyana (peacock plant), C. ornata, C. roseopicta, C. 'Corona,' C. rotundifolia, and C. rufibarba would all qualify, among several others. The only two I can think of that don't have a contrasting underside are C. concinna and C. zebrina. None are particularly recommended as houseplants, for a number of reasons.
• Some Columnea species / varieties have red undersides; the only one I know of specifically is C. orientandina, and its leaves are only red underneath at the leaf tips. Columneas seem to grow okay for me, though I've only had any since spring; other people appear not to find them terribly difficult. (suggested by allandrewsplants)
• A handful of Euphorbia species have green leaves with red-violet to violet backs: E. millotii, E. pachypodioides, and Synadenium grantii;³ Synadeniums are typically either uniformly green with red flecks or uniformly red-violet, but there are plants out there which are green with a red-violet flush on the undersides of the leaves. I have only grown Synadenium, which is ridiculously easy; I don't know what the other two are like in cultivation. (suggested by Sentient Meat)
• Geogenanthus poeppigii (seersucker plant; formerly G. undatus) has highly textured leaves (texture is similar to Peperomia caperata) which are dark green with silver stripes on top and purple underneath. I don't know what it's like as a houseplant; I don't think I've ever even seen it for sale, but it's in a lot of the books, so people must have grown it once.
• Tahitian bridal veil, Gibasis geniculata, has small green leaves with purple undersides when grown in good light, and is a fairly easy-to-grow, if messy, plant.
• Homalomena 'Purple Sword' has broad leaves, mottled in green and gray, with purple backs and petioles. (It is, for some reason, often sold as an Aglaonema or Schismatoglottis; there doesn't seem to be much consensus on the ID, from what I could find on Google.) I haven't been happy with the Homalomenas I've tried to grow (though 'Emerald Gem' and I did eventually reach an understanding), and I've never seen a Schismatoglottis for sale so I assume they're probably difficult as well. Aglaonema and I get along great, which is a major part of my concluding that the plant in question is probably not an Aglaonema. (suggested by tay696 as Aglaonema)
• Hoya curtisii has small heart-shaped leaves which are marbled green and silver on top and flush brownish-red on the underside in certain conditions. I've never grown one, but assume their care is similar to that for other Hoyas. (suggested by Tigerdawn)
• In bright light, Maranta leuconeura var. erythroneura (prayer plant) leaves will have a red back. The other varieties of M. leuconeura never have red undersides, as far as I know. Not recommended, though people do grow them.
• Monadenium rubellum (sometimes M. montanum var. rubellum) is an unusual caudex-forming succulent. The leaves are green with dark red undersides. I've never seen one for sale or tried to grow it.
• Musa zebrina has large green leaves which are splotched with red above and solid red below. I've never tried to grow this one, either, but I would guess it's probably fairly difficult indoors. They may be grown outdoors during the summer and then brought in to go dormant during the winter.
• Paphiopedilum delenatii and some other Paphiopedilums have reddish-purple backs on the leaves, at least in some conditions. Not recommended for beginners, but growable. (suggested by orchideya in comments)
• Peperomia rugosa has glossy, bumpy, olive green leaves with a red underside. I don't know how it is as a houseplant, but I'm about to find out 'cause I just got one. (I didn't know what it was, or I wouldn't have. I'd been hoping to find out that it was a Begonia with atypically symmetrical leaves.)
• Pereskia aculeata cv. 'Godseffiana's (lemon vine, yellow rose cactus) leaves aren't so much green on top and red underneath as they are yellow on top and hot pink underneath, but I figure it's close enough. I've only had one briefly (since May), but I like it a lot, and all indications are that it's going to be an easy plant.
• Philodendron linnaei is sometimes, but not always, green with a purple underside (possibly light-dependent?). It doesn't seem to be sold very widely, so I have no idea what it's like as a houseplant.
• Philodendron mexicanum has glossy, long green leaves with a red back, and is pretty easy to grow.
• Plectranthus ciliatus (candlestick plant, blue spur flower) develops a purple underside in strong light; I had trouble finding a way to get enough light on my plant, when I tried growing it indoors.
• Plectranthus x 'Mona Lavender' leaves are green on top and dark purple underneath. Easy to keep alive indoors, but best color requires ridiculous amounts of light. My main problem with them has been water-related: a potbound plant dries out too quickly, but when I repotted, the plant died. (suggested by Don and Kapt'n Splash in comments)
• Many but not all Saintpaulia (African violet) varieties will get red undersides to the leaves under good conditions. Saintpaulia and I have a troubled history, so I don't recommend them personally, but many, many people get along with them very nicely, and hey, you might be one of those people.
• Saxifraga stolonifera's (strawberry begonia) leaves are gray with a red back. It's usually a very easy plant; mine are being weird at the moment and I'm not sure why.
• Stromanthe sanguinea 'Magicstar' has dark green leaves with white flecks and a red-violet underside; 'Triostar's leaves are pink underneath and irregularly brushed with white and green on top. Both are approximately Calathea-level difficulty; I've been successful with mine, over reasonably long periods, but not everyone is so lucky.
• Syngonium erythrophyllum has dark green leaves with red undersides; I have only ever seen it for sale on the (now defunct) Asiatica Nursery and have no idea what it's like as a houseplant. (suggested by tay696 as Syngonium)
• Some cultivars of Tradescantia zebrina (green/silver on top, red-purple beneath) or Tradescantia fluminensis (dull olive green on top, purple beneath) qualify. It's also possible to turn a T. zebrina that's supposed to be purple green by not giving it enough light; I think in those cases the underside turns green too, but it's been a while since I've seen it so I'm not sure. T. zebrina is easy to grow, if prone to running a bit out of control; T. fluminensis didn't do well for me indoors the one time I tried it. (T. zebrina suggested by Tigerdawn)
• -->I'm open to other ideas, if anybody can think of other plants that fit the category.<--

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¹ "Bamboo ginger" is also the common name of Costus stenophyllus, which looks nothing like this and has leaves which are solid green on both sides. Just so you know. ² Except maybe for Zingiber malaysianum, which did very nicely for me for a very long time, though we're having some relationship problems at the moment. Some of this is Sheba's fault. ³ (Which is technically Euphorbia umbellata now, but sometimes I have trouble letting go of the names.)