To Sarah Mary and Lance:

It occurred to me today at work that if y'all 1) are still having trouble tracking down any Araucaria bidwillii plants of your own, and 2) live in the United States, I could just buy the two we have left at work and mail them to you, in exchange for whatever the sum of postage and the cost of the plant happen to be (I'm guessing about $15 altogether, though I don't actually how much it would be to mail them; it might be more or less than that. The plants themselves would cost me $5.89 each. I'm thinking maybe $8 to ship?)

I don't know what happens to the laws when you try to ship plants over a national border, but I'm guessing they're complex enough to be prohibitive. Also might not want to ship to the Desert Southwest right now, the heat being what it is. (Isn't that right, Aiyana?) That wouldn't preclude doing it later.

These would be the plants in question:


If either or both of you are interested, e-mail me (do actually read the e-mail address, though, first: there are instructions.) and we'll get addresses and stuff.

And if you're not interested, no big deal. You don't have to be.

Cedar Rapids (pictures)

The husband and I went to Cedar Rapids on Friday: I'd wanted to check on Pierson's, to make sure they'd come through the flooding okay, and also to look at plants that I didn't have to take care of, and we both sort of wanted to look at the downtown area to see the extent of the damage for ourselves. Which was, yes, gawking. Well before we were done, I was pretty ashamed: feeling a pretty strong sense of we should not be here, now.

There are, of course, huge chunks of town that were more or less unaffected, where business proceeds as usual, but in the parts of town that were affected, I didn't really have to aim the camera. Any direction I shot was going to show something. So, without further ado, I give you Cedar Rapids as of June 27, 2008:

Downtown is full of guys running around in white hazmat outfits, big dumpsters on the street, and lots of cleaning companies, dehumidifiers, etc. Traffic moves, but slowly, and all the equipment narrows the streets down considerably from what they usually are like.



The message is "WE HOPE OUR LOSS GIVES U SCENIC PLEASURE." Interpretable in more than one way, but it doesn't, you know, sound particularly friendly. I was assuming it was sarcastic, which made me 1) want the picture more and 2) feel more ashamed of taking the picture.

Piles upon piles of garbage. Siding, washing machines, tires, chairs, paper, swingsets -- all the stuff you've got in, on, or around your house, soaked for a week and a half in toxic water and then collected in piles.


Something that fails to show up well in the pictures: everything's also covered in dirt. I mean, in the pictures it looks like just a road, but in person, it's muddy and smelly and neverending.





Houseboats on the (still very high) Cedar River. Can't really tell from looking at them what kind of damage they sustained, but it's obviously not all fine.


And then the part that shocked me: Pierson's. The business is not gone altogether, because they had two locations: this one, the original, which was where the tropical plants (most of them, anyway) lived, and then another one elsewhere which seemed to be mostly for flower deliveries. The latter is far from the river and therefore fine, but the original location is basically ruined. Some plants barely visible in this pile: some unknown bromeliad, a sago palm, a croton.

A couple panes of glass were broken in the greenhouse: I couldn't really see much in there, though it was obvious that there were plants in it still. I couldn't really tell if they'd moved anything out or not: either a bunch had been taken away before the water hit, or else a bunch fell over in the water and nobody had been in the greenhouse to pick them back up yet.
Couldn't make out much of what was going on inside the store, either, though some of the walls didn't look like they were there any more. I could kind of make out a couple studs with debris hanging off of them.

Pierson's is especially sad to me because I can relate: Pierson's is to Cedar Rapids more or less what my employer is to Iowa City, and we were at one point expecting to get more or less what they got: we just dodged the bullet. Plus, on a completely self-interested note, I now have that many fewer options when I want to go out of town and buy a tropical plant. But it's hard to look at that and not wonder what they're all going to do. I mean, the oldest greenhouse was indeed very old, and if they were insured, then they might be better off in the long run to be rid of it and build a brand-new one. But how likely is it that they were insured? They were only a block from the river, it turns out (seems longer, somehow, driving to them). So maybe.

I was kind of telling myself while taking pictures and feeling ashamed that it was okay, karmically, because I was going to be posting them for other people to see, and that meant there'd be help coming, and I was therefore doing something useful even though I wasn't, you know, doing anything useful. But that's kind of a crock of shit. I mean, people knew there was a flood anyway, help was already coming. I was just taking pictures because there didn't really seem to be much else to do, because it was too much to take in all at once, because it was impossible to look away. It's pretty overwhelming in person.

Caveman (Araucaria bidwillii)

Two species of Araucaria are used as houseplants: A. heterophylla, also known as the Norfolk Island Pine, and A. bidwillii, which is also known as . . . well, it's not really known as anything, because they're pretty uncommon indoors. Though outdoors, they're called "Bunya-bunya" trees. Sometimes. Mostly in Australia.


We'll get to some reasons why they're uncommon,¹ but first, let me try to impress upon you exactly how old this genus is. Fossils of Araucaria, often in the form of petrified seed cones and wood,² are known from the Jurassic period (135-180 million years ago). I had difficulty finding any solid numbers on ages, but fossil Araucarias from 220 million years ago are apparently not unheard of. These, it should be noted, are not the modern-day A. bidwillii, just a tree from the same genus.³ Even so, this is a long time for a genus to survive, and bidwillii is a close enough relation to the fossils that even a non-expert can see a resemblance (see the link here).

Petrified log at Petrified Forest National Monument. Photo by Jon Sullivan, listed at PDPhoto.org and found through Wikipedia. This is probably not a petrified A. mirabilis: mirabilis is apparently mostly found in South America.
Most of us have no real concept of how long ago 220 million years ago was, and I can't think of any good way to explain it, because I'm one of most of us. Maybe it's just me, but I've always been left somewhat cold by analogies like, 220 million inches is . . . whatever it is, or if every year were shrunk down so it took only a second -- it's better than nothing, kinda, but I have no intuitive feel for those kinds of numbers; I don't have everyday experience with circling the equator sixty times or 180,000 years or whatever either. So what to do? Let's try something else:

Araucaria spp. are so old, when the species first differentiated, the Dead Sea was only beginning to get sick.

No? Lemme try again:

Araucaria spp. are so old, John McCain climbed them as a child.

Over the line? Okay, one last try:

Araucaria spp. are so old, the first ones had to grow in the dark for three years before God finally said, "Let there be light."⁴

But more seriously: the Araucaria genus is so old, dinosaurs could have eaten them (and presumably did. I mean, something must have). They survived an asteroid striking the earth, mass extinctions, continents sliding around the earth like butter on a hot skillet, and multiple ice ages. This is an old group of plants.

So have some respect, I guess is all I'm saying. Araucaria was here first.

Adult Araucaria bidwillii. Photo by Wikipedia user Bidgee, taken of a 100+ year old tree in Collins Park, Wagga Wagga, New South Wales, Australia.

The tree is presently native to parts of Queensland, Australia, where it lives in rainforests. It has also been widely introduced outside of its native range, though, and cultivated specimens can be found on the U.S. west coast, the U.K., New Zealand, and parts of China. Specimens can get to be several hundred years old (600 is a pretty safe guess, according to one source) and a good 50 meters (164 feet) tall. It also has nice, straight stems, which produce nice, straight lumber, though logging mostly ended in the 1940s when the Australian government realized that if the remaining bunya-bunya habitat wasn't declared a national park or something, the species was going to be completely exterminated. Being sensible people, they made a park out of it.⁵

The bunya-bunya has mainly been of interest to humans for something else, though: its seed cones. Plants begin to bear cones at about 14 years of age. The seed cones resemble pineapples, though they're larger and rounder and can weigh as much as 4.5 kg (9.9 lb).⁶ Each seed cone (and there may be about thirty of them on a given tree) contains somewhere between 50 and 100 unusually large, edible seeds. There's a reason for the unusually-large part: we'll get there later. In any case, thirty cones to a tree, with maybe six pounds of seeds per cone, times however many trees are in the area, means lots of food available all at once, and whenever there's lots of food available at once, that means party. The catch is that this only happens every three years or so.

Seed cone of Araucaria bidwillii, partly torn apart. Photo by DRyan at the Wikipedia entry for Araucaria bidwillii.
In the years when the cones were being produced, the "custodians of the trees" would send around messengers to invite neighboring tribes to assemble near the trees. This would usually happen from January to March (Southern Hemisphere summer). The custodians would cut deep gashes in the sides of the trunk for traction (though occasionally this wasn't necessary because vines around the trunk could be climbed instead), and then they'd climb the trunks and knock the cones out of the tree canopy. The cones will fall on their own, too, of course, though this is not only inconvenient (only the tree knows when it's going to let go), it's seriously dangerous, too: a ten-pound cone falling 150 feet is going to have enough momentum behind it to kill a person.⁷

A lot of important business was conducted on these occasions: people hunted, arranged marriages, got into fights, held religious ceremonies, resolved conflicts, cheated on spouses, traded goods, shared ideas, made friends, and (I'm assuming) gossiped like crazy. (You know, the normal stuff that people do when they're in large groups that haven't seen one another for a long time.)

The nuts themselves can be eaten raw, roasted on coals, or ground into flour, and are supposed to taste like chestnuts. One site likens the texture to that of a waxy baked potato, which furrows my brow a bit. As partiers returned to their homes, they would bring nuts along with them (though it seems like they'd be pretty sick of them, after eating so many), burying a few here and there along the way.

Both the seeds and the early sprouts can be eaten, which brings us to the promised explanations for 1) why they're not common houseplants and 2) why the seeds have to be so big. You see, Araucaria bidwillii has a very roundabout way of germinating. First, the seed sends a root out, I guess to anchor itself and collect water, and then it grows a tuber, and eventually the tuber grows a first shoot, though this can take a long time, anywhere from two to twenty-four months. The first shoot is rosette-shaped, and has brown leaves; the plant grows green leaves and starts growing upright later. There's pretty wide variation in the length of time for any of these steps, which makes them frustrating plants to try to grow from seed, which is part of the reason why they're uncommon in cultivation: nobody wants to invest that kind of time for a plant that's that ugly. It's not like customers are breaking down doors to buy them.

My personal plant, from late October 2007.
Speculation abounds as to why the plant might have evolved such a roundabout way of germinating; protection against fire is one possibility. Another idea that's been floated is that maybe by building up a reserve of food in the tuber underground, the seeds are enabling a rapid push through and above neighboring plants, increasing their odds of survival, and by stretching out the germination period over a long time, they're hedging their bets as to when a good time to emerge might be. Neither of these satisfy me as an explanation: it seems to me like it took a lot of time and energy to build the seed in the first place, so why take that investment and make it burn even more time and energy rebuilding itself in the form of a tuber?

In any case, you'd need a large seed to be able to sustain itself over the two-year (potentially) germination process, hence the large seeds.

The tubers are edible as well, by the way, and are said to have a coconutty flavor. (Now I'm picturing a potato that tastes like a coconut, and finding it even harder to imagine than a nut that tastes like a waxy baked potato. Way to top yourself, A. bidwillii!)

My own personal plant has not done any head-bonking, and I haven't eaten it either, and it's been, altogether, a lot less dramatic than the above would indicate. In fact, I had trouble convincing it to do anything at all for several months after I got it.⁸ Then when we started opening the apartment windows in the spring, it kept getting blown off the shelf onto the floor: the soil it was in dried out incredibly fast, and was pretty lightweight to begin with, and so eventually we had to just stop opening that particular window. All the falling on the floor seemed to be good for the plant, though: it sprouted some new growth shortly afterward. Sometimes it helps to give them a good scare.

It still wasn't a fast grower, but at least there was something, and then it pretty much stopped again for a while. Since this spring, it's been growing pretty well, though, and has added another couple tiers of branches.

My personal plant as of 25 June 2008.

I'm not sure what to expect it to do next, whether it's going to continue its current rate of growth or whether it's going to stop again at some point and regroup. Either way, Araucaria bidwillii isn't a good plant for someone who wants to see a lot of fast, intense growth year-round.

I can't say we've had any major conflicts about care. When I bought my plant, I was pretty much flying blind: there's not much information out there about caring for it as a houseplant, and so I basically just treated it the same as an A. heterophylla, and that worked out just fine. This has been refined a little bit in the subsequent months, though:

Pests: Never had any issues with pests on this plant, either at home or at work.
Watering: The plant doesn't seem to be extremely inconvenienced by droughts, though I usually don't let mine go more than a week between waterings. I know it's possible to overwater them, because we've done that with some at work, but my personal plant is in such fast-draining soil that this isn't something I worry about at home.
Light: The ones at work sometimes go a bit yellow (even verging on orange), which I think is from getting too much light or heat or both. Bright indirect light with some direct sun appears to work fine at home.
Propagation: Supposedly Araucaria spp. will root and grow from a branch or tip cutting, but I've never tried it, and the results from branches are supposed to be very goofy looking. Seeds, if you're lucky enough to come by seeds and you don't eat them all, will yield better-looking plants, in theory, but will also take years, potentially, just to reach the pitiful stature of my plant pictured above.⁹

Araucaria bidwillii in 3-D, for those people who can cross their eyes properly. (The picture works like one of those Magic Eye pictures that were all the rage a while back: you have to sort of cross your eyes such that the two images overlap one another in the center of your vision, at which point, in theory, your brain should take over and interpret this as a 3-D image.)
Humidity: As far as I can tell, A. bidwillii is pretty much indifferent to humidity, though naturally, in the rainforest, they would be accustomed to it. Also their relatives (A. heterophylla, e.g.) like it, so it's something that could be helpful for an ailing plant.
Temperature: They're said to be hardy down to about 20ºF (-7ºC), though I haven't tested this myself. Excessive heat doesn't seem to be a huge problem either, though like I said, I suspect either too much heat or too much light of causing some bleaching and yellowing on the plants at work.
Grooming: Picking off dead branches as they occur, I suppose. I have yet to lose a branch on my plant at home. Very old plants lose branches as a matter of course, changing from a cone-shaped tree to a tree with a rounded canopy at the top of a long trunk, though that's not something you'd have to worry about indoors.
Feeding: Unless I hear otherwise, I'm going to assume that the usual houseplant feeding routine applies here: a little shot of 20-20-20 every three months or so, possibly skipping winter, should be good.

It seems to be normal for leaf size to vary like this.

As indoor cultivation goes, I'm not going to argue that it's the prettiest or easiest tree. It isn't going to give you flowers, the leaves are sharp if you encounter them at the wrong angles, and it's not likely to become the nice symmetrical plant that its relative A. heterophylla is. But you could do worse, and what it lacks in aesthetics it sort of makes up for in history and strangeness. History and strangeness can be their own beauty, sometimes.

Seen from above.

-

Photo credits: As attributed in text.

References: http://www.pfaf.org/database/plants.php?Araucaria+bidwillii
http://www.cityofdunedin.com/city/?page=bgplant_bunya
http://www.conifers.org/ar/ar/bidwillii.html
http://tree-species.blogspot.com/2008/06/bunya-pine-araucaria-bidwillii.html
http://en.wikipedia.org/wiki/Araucaria_bidwillii

¹ One site I visited attributed this to A. bidwillii being, basically, ugly compared to A. heterophylla, though they didn't phrase it quite like that. In any case, I think it was uncalled for.
² Petrified Forest National Monument, in Arizona, contains hundreds of acres of petrified Araucaria logs. These are actually a bit older than most: they date from the late Triassic period, which means the trees in question died more than 200 million years ago. [Sidenote: the identification of the logs as Araucaria is somewhat contentious, with some scientists preferring Araucarioxylon instead. The two aren't interchangeable, but they are related, which is close enough for me. And also, there are actual fossil Araucarias which aren't controversial, in South America.]
³ They're actually a little bit more closely related than that, because they're also in the same section, section Bunya: I'm a little unclear on where sections fit into the hierarchy of species, genus, family, etc., but it looks like a subdivision somebody stuck in between genus and species: all Araucarias are related, but some are more related than others. Why is this a distinction worth making? Damned if I know. But to return to the original point: although the fossil Araucarias known from South America are in fact not Araucaria bidwillii, being instead an extinct species named A. mirabilis, Araucaria bidwillii is their closest living relative. And yes, there are people who study fossilized plants as an occupation (called paleobotanists), and I'm willing to bet you large sums of money that they take this kind of thing very, very seriously.
⁴ You know, I tried coming up with original jokes, but the only one I came up with on my own was the McCain one, and it kind of writes itself, really. For the rest of them I had to resort to modified Yo Mama jokes, which is not as easy as it sounds. Very few jokes in the Yo-Mama-is-so-old mold can be adapted to fit trees.
⁵ Technically, they expanded the boundaries of an existing park, Bunya Mountains National Park, which had been established in 1908.
⁶ Though the cones are individually either male (produce pollen) or female (produce seeds), the plants themselves produce both kinds. I ran into a contrary claim during research, saying that the species was dioecious (having separate male and female individuals, as for Rhapis excelsa), but I believe this is not true.
⁷ Before settling on "caveman" for the "person" for this species, I was considering "grandma," because grandmas are the only people I could think of who are very old and routinely try to kill you by giving you too much food. Caveman won out because this is too spiky of a plant for "grandma" to seem appropriate, plus cavemen are that much older and are known to enjoy bonking others on the head, which [most] grandmas are not.
⁸ After researching for this post, I suspect that at least some of the problem was because I repotted it shortly after getting it home. Young plants are said to have fairly delicate root systems, so I may have set it back inadvertently.
⁹ Incidentally: Pierson's, in Cedar Rapids, at one time had an Araucaria bidwillii about three and a half or four feet tall, for which they were asking $59.95. This is a pretty damn good price, considering how much time and work it would take to grow one to that size yourself. The only catch is that I'm not positive that Pierson's stayed above water in the recent floods: they were close enough to the river that I worried, but far enough away that I haven't yet called to check up on them. Since I saw a Pierson's delivery van in Iowa City yesterday (which would have been notable even without the flooding), I'm guessing that they survived, but again, I haven't called to ask.

Random plant event: Lisianthus 'Mermaid Pink' turns splotchy

I know I said the Araucaria bidwillii profile would go up today, but I just didn't have the time to quite finish, plus I was having some issues with the heat yesterday (not sick so much as just tired), so it's been postponed. Hopefully tomorrow. In the meantime, check this out.

I don't really have any context for this; I'd never even heard of Lisianthus until maybe three months ago. All I know is, one of the varieties called 'Mermaid Pink' ordinarily looks like this:


But there's one particular specimen that doesn't, and instead looks like this:


I think this looks pretty awesome, but I'm guessing that it's probably a virus or something causing the splotchiness, and therefore isn't really a cool development at all.

But pictures don't hurt anything, right?


Very fond of the Lisianthus, by the way. They took forever to do anything, granted, but sometime during the flooding, the two short varieties we have all went into bloom kind of at once. (Still waiting on the tall ones.) It was pretty cool to come back to. WCW tells me that they're touchy about being too wet, which means the ones around here probably aren't doing well this year (we actually got another big splash of rain last night, maybe 3 inches, and there's supposed to be about that much again over the course of the next few days), but I definitely see the appeal.

Random Plant Event: Disocactus (?) NOID blooming

UPDATE 4 Aug 2009: The plant in this post is in fact not a Disocactus. What it is, is a Pseudorhipsalis ramulosa. It was sold to us (where I used to work) as a Disocactus, so that's what I called it. I would rewrite the whole post to reflect this, but that would be an awful lot of work to go to for an old post that nobody is likely to read anyway, so instead I'm saying this. Sorry for any inconvenience and/or confusion.

This is a Disocactus. I initially misunderstood it as Discocactus, but no, Discocactus, though it actually does exist, is a different thing. (It looks more or less like a regular barrel-type cactus, with spines and ribs and all. Another way to tell the difference: when grown in good conditions, sometimes a Discocactus has to boogie oogie oogie 'til it just can't boogie no more. Though this is rare.)


At least, I thought it was a Disocactus, because that's how it was sold to us. And also 'cause WCW said it was, and she's almost always right about these things.

They're nice enough in their own right as plants, of course. In full sun, they change colors from green to red, which is kind of pretty (though I think it takes a lot of sun), and if they'd been just a slight bit smaller and cheaper I probably would own one, but I don't.

We also had a customer in a while back who wanted to know what kind of Disocactus we have, because apparently they come in kinds. There are some that have red flowers, and some that have yellow, or white, and some of the flowers are big, or small, or etc. I had no idea. Neither did WCW.



Then recently, they started growing little bumps along the edges of the leaves, which was weird but not really noteworthy: for all I knew this was an alternate way they budded off new stems (or leaves, or whatever they are).

Then the bumps turned into flowers. So now we know: white. Also tiny. I'm a little disappointed that they're not more dramatic, but at the same time, well, it's something new.


It may yet be, WCW's considerable expertise aside, that these aren't technically in the Disocactus genus: I wasn't able to find anything that looked like these in an admittedly hasty and non-thorough search. I found better likenesses among the Rhipsalis and Epiphyllums. I'm not betting against WCW: I expect this just means I should do a more comprehensive search.

Pretty picture: Pulmonaria 'Raspberry Splash'

I really don't care whether Pulmonaria flower or not; I just love the leaves. Not so crazy about their slightly prickly texture (I get itchy if I have to move them around on a table), but I love the leaves.


A favorite perennial? Well, I don't know. We probably shouldn't get carried away. I mean, there are some very nice Hostas and Euphorbias, and Hemerocallis is occasionally awesome. I could go on. But Pulmonaria has to be up in the top ten, at least.

Is the plant an accomplice?

Man attempts to rob store with palm frond.

It didn't work.

The tree, apparently, had no comment for the press.

(Via BoingBoing.)

The War With the Spider Mites

I've mentioned before that there are only seven primary houseplant pests. In descending order of seriousness (in my admittedly subjective opinion), they are:

1. mealybugs,
2. scale,
3. whitefly,
4. spider mites,
5. aphids,
6. fungus gnats, and
7. thrips.

The first three on the list (mealybugs, scale and whitefly) can be very serious problems: they are very contagious, they multiply quickly, and they can cause a lot of damage. The last three (aphids, fungus gnats, and thrips) can be problems under certain circumstances, but indoors, you can either get rid of them pretty easily (aphids), they don't really cause much damage in the first place (fungus gnats¹), or you're unlikely to run into them (thrips).

Spider mites occupy that special middle rung, where they're very contagious and multiply quickly, and they can cause real damage, but at the same time they're not necessarily that big of a deal. The severity of a spider mite problem depends hugely on A) what plant is affected, and B) what the general growing conditions of the plant happen to be: change the plant or the conditions, and you have an entirely new ballgame.

Spider mites on a Ficus elastica.
So let's start with the basics. What is a spider mite?

Spider mites are not insects. What they are is arachnids, which means they're more related to spiders, daddy-longlegs and ticks than they are to flies and beetles. (Forgive the pedantry, but this sort of thing actually matters sometimes.²) And if you look at them closely (if you can look at them closely), this is actually pretty obvious, especially the resemblance to ticks. So there's that. Spider mites are all in the family Tetranychidae, and there are about 1600 species in the family, wikiposedly, though most of these are not abundant enough or hardy enough to pose a problem for cultivated plants.

The most common species of spider mite is Tetranychus urticae, usually called the two-spotted spider mite. It can be various colors,³ but most of the time when I've seen them, they've been red, beige, or brown. There are very, very few good pictures of them on-line, for the simple reason that they're very tiny, plus they move around, so it's difficult to get a good, well-focused shot, and if you do get a good shot, you're usually so close in to the plant that it's difficult to tell what parts of the picture are the mites and what parts are the plant. Though in cases where the background is all the same color, it's easier:

Spider mites on a Catharanthus roseus flower.
Fortunately, one doesn't need to see the mites themselves to know they're there. The usual first sign of an infestation is that the plant just starts to look kind of tired. The leaves in particular get a dusty or bronzed look to them, and close inspection of the leaves will probably show both a little actual dust and dirt, plus a bunch of very tiny yellow or gray spots, which are what give the dusty look. The spots are plant cells that have collapsed and died due to the spider mites' feeding. The mites pierce the cell walls with their mouthparts, suck out the liquid, and then move on when sated. The cells are unable to repair the damage, and consequently die, leaving a tiny gray or tan spot. Multiply times ten gazillion, and you have faded-looking leaves.

Mite damage to an Aspidistra elatior from work.
If you suspect spider mites from looking at the top of the leaves, looking underneath will generally confirm it. In very advanced cases, you'll see some webbing underneath, usually visible because it has "dirt" sticking to it. The "dirt" may be actual dirt that's been splashed up during watering of the plant, in which case it's no big deal, or it's mite droppings, which isn't a big deal either but it's kinda gross. Once you've seen both a few times, it's pretty easy to tell the difference. (As a rule, actual dirt will crumble and fall at the slightest touch, and embedded droppings will stick until you wipe them off with a finger.) Should also note that I know this mostly because I do basically all my watering at home and at work from overhead, which is a splashier process than using a watering can like a civilized person would, and leads to more dirt hanging from the undersides of leaves than you probably have on your plants.) In very very bad cases, especially if it's hot, you'll see the mites themselves running around.

Spider mites are, at least in theory, capable of living off of any plant, but in practice they're limited to those with fairly thin, easily-penetrated leaves, so your cacti and succulents are safe. Even among thin-leaved plants, they have some strong preferences for particular kinds.

It's impossible to come up with a comprehensive list of which plants are the bad ones for spider mites. That said, there are a handful of plants that I, customers, or people I know refuse to attempt anymore, because of spider mites, so I guess they're good candidates for the worst of the worst. Those unlucky few are:

Aspidistra elatior (cast-iron plant),⁴
Calathea spp., including Calathea ornata,
Codiaeum variegatum (croton),
Hedera helix (English ivy),
Schefflera actinophylla ,
Schefflera arboricola , and
Schefflera elegantissima (Dizygotheca elegantissima, false aralia).

I've got a list of other mite-prone plants. The list is long, and hard to make interesting, so I'll stick it in a footnote rather than ask everybody to read through it all.⁵


Ordinarily you'll find that mite problems are cyclical, recurring things, rather than a full-scale battle all year long. Mites have certain environmental conditions they prefer, and if you can make things less to their liking, they'll slow way down or even sometimes disappear entirely. This is the good news, if there is good news.

Mites prefer hot, dry conditions and stagnant air. Change a part of this equation, and you can accomplish a lot. If your home must be dry and stagnant, try cooling it down. If it must be hot and dry, at least get some air moving. That kind of thing. Another option, if you have a space available, is to move your plants outside for the summer: in a lot of areas, outdoors may be hot, but at least there will be humidity and air movement.

Most spider mite problems indoors start in the fall and last through the early spring, when homes are being heated, the humidity level is low, and moving plants outside isn't really an option. I had relatively good luck at home last winter using a humidifier (I still had mites, but it was a lot less of an issue than it had been the winter before.). Misting and pebble trays are better than nothing, though (in my opinion) not by much.

Another Catharanthus picture.
One can also try poison, of course. In the greenhouse at work, we spray miticides weekly, but for all the good it does us we could be spraying hopes and wishes; I think we're selecting for miticide-resistant mites, not keeping a pest population under control. And I have said so. And I am being roundly ignored.⁶ Last winter, we had a particularly bad plague sweep through the larger crotons (small ones were fine), most of which lived through it, but of course then they looked like crap, and they're only just now beginning to come back. Last fall, it was the banana (Musa) trees and the Alocasia 'Polly.' During the spring, it was some of the annuals (particularly Dahlia, Vinca, Angelonia, Nemesia, Alternanthera, Catharanthus roseus).⁷ At the moment we're pretty close to clear, though we've been preoccupied by the flood, too, so maybe there's a problem I'm just not yet aware of. I should probably check the bananas.

Spider mites are known for being able to develop resistance to miticides, so if you do elect to go with poison, my advice (which I do not, myself, follow, not that that makes it bad advice) would be to buy two or three types, containing different active ingredients, and use them in rotation. Using the same product repeatedly may still work: it's just that it's much harder for pests to adapt to multiple pesticides in rapid succession than it is for them to adapt to one: they have to hit a moving target, so to speak.

Other things to try, besides fans, humidifiers, poisons, and air conditioning, include moving affected plants (and any other plants, while you're at it) to the shower to water. It's not that watering from high overhead is any better than watering with a can, necessarily, but water droplets can dislodge the occasional mite, and every mite that gets knocked off is one more mite that isn't going to be laying eggs on your plant.⁸ Some insecticidal soaps also work on mites, though you're probably money ahead to skip the specially formulated "insecticidal" soaps and go with a solution of dishwashing liquid in water, or liquid hand soap in water. The insecticidal soap we sell at work is, if I read the label correctly, more or less repackaged, diluted liquid hand soap, i.e. potassium salts of fatty acids.

There are also oils one could try: we have a product at work that's formulated from cottonseed oil, clove oil, and garlic extract, that I've used sometimes at work. I'm not sure if it's all that effective, really - it wasn't terribly helpful with the bananas last summer - but it may also not have been used as regularly as directed. This sort of product seems to be intended to just annoy the mites into leaving: if they can't walk around or start new webs, because everything's covered in oil, I suppose they might eventually die off as a result, but it seems like it'd be hard to cover every available surface, and the oil does go away after a certain amount of time has passed.

Neem oil, on the other hand, has an actual poison in it, yet is safe to use in the house (more or less. I mean, don't go putting it on your salad or anything.). You still might not want to, as it has a weird smell: to me it smells sort of like peanut butter and garlic and socks. (Your perception may vary.) It has a chemical in it which disrupts the normal function of mites in a number of ways. I've only tried it once on a plant with mites, and the plant recovered (plus it was a Dizygotheca elegantissima, even), but I couldn't say that the neem was what won the battle.

So in conclusion: you are probably going to have spider mite problems sooner or later. (The saying was originally "death, taxes and spider mites.") One should be particularly vigilant with the plants that are known to be especially attractive to mites. If you find mites on a plant, it's not necessarily the end of the world: you have a lot of treatment options. The one thing you can't do is be complacent about watching for them or procrastinating on treatment if you see them, because infestations can flare up in very little time.

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Photo credits: all my own.

Pre-emptive defense against charges of plagiarism: I just want to say for the record that this article has certain similarities to the corresponding article at Water Roots, including the assertion that some plants are more mite-prone than others and the metaphor of warfare. This is not because I plagiarized from said article; it's just that, you know, some plants really are more mite-prone than others, and the only metaphor that really works is warfare.

¹ I know, I know, fungus gnats killed your sycamore tree. Fine. Whatever. Bad fungus gnats.
² Among other things, mites not being insects is an indicator that the chemicals that will kill insects (like mealybugs, whiteflies, etc.) will not necessarily kill spider mites. It also, obviously, suggests that if you use a miticide in the greenhouse, you run a strong likelihood of killing any spiders, ticks, or daddy-longlegs that happen to be around too. It's hard to get sentimental about ticks, but how anybody could want the daddy-longlegs dead is beyond me.
³ According to the stuff I've found in the research for the post, the color of spider mites depends variously on what and how much they've been eating, the time of year, and the point of the life cycle a given individual happens to be in. Green, brown, tan, beige, translucent, red, red-brown, and probably others I can't think of right now are all options. The "two spots" in the common name may or may not be present.
⁴ I think under normal circumstances Aspidistra elatior is usually okay, because people don't usually bring lots of plants in and out of their home all the time. We have trouble with the ones at work because new plants are always being brought in, any one of which might have a mite or two on it, plus we always have a few lingering somewhere in the greenhouse, and the plants get rearranged a lot. So, however good a job we do at keeping the Aspidistras clean, inevitably there's going to be a new population springing up. It's been enough to put me off of buying one, though the A. lurida 'Milky Way' I had previously is still okay, knock wood. I do not know whether A. lurida is supposed to be better with respect to mites than A. elatior, but so far it does kind of look that way.
⁵ Other plants which are rumored to be exceptionally mite-prone, or which I've actually experienced having mites on: Anthurium andraeanum, Araucaria heterophylla, Aspidistra lurida 'Milky Way,' Caryota mitis, Chamaedorea elegans, Chamaedorea seifrizii, Citrus spp., Cissus rhombifolia, Cordyline fruticosa, Dieffenbachia spp., Dracaena marginata, Euphorbia pulcherrima, Ficus benjamina, Ficus elastica, Gardenia jasminoides, Maranta leuconeura erythroneura, Musa spp., Philodendron bipennifolium.
⁶ (Not that I'm bitter.)
⁷ Lest you think we're terrible people who are selling buggy plants to customers knowingly and on purpose: if I see mites on a plant, I'll say so to the customer and look for another plant of the same variety that's better, or suggest a different variety. I think this is generally the policy for everybody else, too. That said, during busy days, it's not always possible for an employee to inspect every plant that goes out the door, and different employees vary in their familiarity with pest problems, and mistakes do get made, so you should always always always do your own inspection too. Or at the very least you can ask the cashier to look when you're buying, if s/he doesn't do so spontaneously. I doubt that this matters a whole lot when it comes to annuals, because once people plant them outside and they've got some air movement, I think the spider mites generally go away anyway; it's only an issue because we have to keep some of them in the greenhouse, and the greenhouse gets very hot and dry sometimes:
Outdoor temperature: 85F/29C. Greenhouse temperature: 104F/40C. Greenhouse humidity: 60%. Heat index in greenhouse: 145F/63C.
Also, while I'm here: although Alternanthera is in the list of things we had trouble with in the greenhouse, spider mites don't seem to go for my Alternantheras at home any more than they do for the rest of my plants. Not sure how to explain this, but it's possible that the variety at work is just an extra-delicious one.
⁸ I've seen the claim made that spider mites are "born pregnant;" this is not the case. They lay eggs. The person making the claim was probably thinking of aphids, some of which are born pregnant. Not sure about thrips, but whiteflies, spider mites, scale, mealybugs, and fungus gnats all lay eggs.

Pretty picture: Two orchids

Odontoglossum 'Margarete Holm'
This was going to be a post of just one flower by itself, but I'd forgotten that the quality on the above picture was kind of lacking. So you get a second one, in the hopes that one or the other of these pictures will be satisfactory:

Miltonidium Bartley Schwartz 'Highlander'