List: Houseplants Which are Highly Prone to Spider Mites

There's no official or definitive list for this; spider mite susceptibility isn't something I've ever tried to quantify. That said, though, there are definitely some plants which are more likely to have mites when you buy them, or more likely to develop a raging case of mites once you get them home.

Thick-leaved succulent plants and cacti tend not to have mite problems; spider mites don't seem to be able to pierce their thicker, waxier epidermises. Consequently, the plants most susceptible to mite attack have broad, thin leaves (like Musa or Dieffenbachia) instead of small, fleshy ones (like Crassula or Hoya). Certain families are apparently also a lot tastier than others; the Araliaceae, Marantaceae, and Apocynaceae seem to be particularly delicious.

(I realize that it would probably be a lot more useful to the reader to present a list of plants which are highly resistant to spider mites, as opposed to plants highly susceptible to them, but that's actually much tougher to do. Even if I've never seen a bad mite infestation on, say, an Aglaonema, I can't really be certain that they're that resistant. Maybe the Aglaonemas with whom I've personally been acquainted have just been really lucky, you know?)

Alocasia 'Frydek.' (also other Alocasia spp.)

Aspidistra elatior 'Milky Way.' (cast-iron plant)

Calathea roseo-picta, possibly cv. 'Rosy.' (also other Calathea spp.)

Chamaedorea elegans. (parlor palm)

Codiaeum variegatum 'Petra.' (croton) (also other Codiaeum variegatum cvv.)

Cordyline fruticosa 'Kiwi.' (ti plant) (also other Cordyline fruticosa cvv.)

Assorted Hedera helix (English ivy) cultivars.

Pachypodium lamerei (Madagascar palm).

Schefflera actinophylla (umbrella tree).

Strelitzia nicolai. (white bird of paradise)

Severity of infestations vary, enough that I really adore some of the above, and refuse to let others in my home. I consider Cordyline fruticosa worth the trouble, and both Pachypodium and Strelitzia are welcome, because they tend not to get out of control mite populations as rapidly as others on the list. Codiaeum variegatum, on the other hand, is a definite planta non grata here, mostly (though not entirely) because of its attractiveness to mites, as are Hedera helix, Calathea spp., and Alocasia spp. All four of those gave us ongoing, substantial problems where I used to work, to the point where I stopped bringing them in. (They've started ordering them again since I left, though, with predictable results.)

Am I missing anything? Let me know in the comments.

Not pictured:
Acorus spp. (sweet flag, Japanese rush)
Adenium obesum (desert rose)
Alternanthera spp. (including A. dentata 'Purple Knight')
Aspidistra elatior (cast-iron plant)
Breynia disticha cvv. (snow bush, snow on the mountain)
Brugmansia cvv. (angel's trumpet)
Chamaedorea seifrizii (bamboo palm)
Cissus rhombifolia (grape ivy)
Colocasia cvv. (elephant ears)
Datura cvv. (devil's trumpet)
Dieffenbachia spp. (dumb cane)
Dracaena marginata (Madagascar dragon tree)
Dracaena thalioides
Gardenia jasminoides (gardenia)
Hedera canariensis (Algerian ivy)
Heliconia psittacorum cvv.
Hibiscus rosa-sinensis (tropical hibiscus)
Impatiens spp. (impatiens)
Jasminum sambac (jasmine)
Maranta leuconeura cvv. (prayer plant, rabbit tracks)
Musa spp. / Ensete spp. (ornamental banana)
Plumeria cvv. (frangipani)
Polyscias balfouriana (balfour aralia)
Polyscias fruticosa (ming aralia)
Primula vulgaris (primrose)
Ravenea rivularis (majesty palm)
Schefflera arboricola (umbrella tree)
Schefflera elegantissima (also known as Dizygotheca elegantissima) (false aralia)
Stromanthe sanguinea cvv.

Saturday morning Nina picture

Pretty picture: Kalanchoe blossfeldiana NOID

The lighting was a little off here, but you get the idea.

Kalanchoe blossfeldiana has now been mentioned a few times at PATSP, and every single time, I seem to feel the need to tell you that I have no strong feelings about these whatsoever. I know this because that's what I was tempted to write this time, but it seemed familiar, so I searched the blog, and found that I'd done that already. Multiple times.

So does anybody else have any strong feelings about K. blossfeldiana I could borrow for a little while? Positive or negative, it doesn't matter. I promise to return the feelings in more or less their original condition.

Random plant event: Nematanthus NOID flowers

Okay, I don't renounce the Gesneriaceae and all its works.

Though the Streptocarpus have broken my heart, the Saintpaulias force all manner of indignities upon me, the Aeschynanthus turns a deaf ear to my pleading, and the Episcia fill me with mortal terror, at least the Nematanthuses appreciate me.


The plant in question was repotted recently, and has been dropping leaves all over the place ever since. Of course, it was dropping some leaves before, too. (Why did I repot, this time of year? I was having trouble keeping it watered, and figured that whatever trauma was caused by the repot would be less than the trauma of drought stress every two weeks.) I hadn't noticed any buds or blooms until I went over to it yesterday to sweep up the dropped leaves, and then I found two. Which is not a spectacular show, but perhaps it's only warming up. The solid-orange Nematanthus (previously pictured) has six blooms in progress on a single plant, four of which are big enough to see. Which actually is sort of a show, or will be soon.

Lawn Ornaments: Frozen Water Balloons

This didn't quite work out as intended, but since I went to all the trouble to do and photograph it, damned if I'm not going to at least squeeze it for whatever blog post juice it might contain.

I borrowed this idea from an anonymous friend. It's pretty simple. You get a bunch of balloons, put a few drops of food coloring in each balloon, fill with water, tie off, and then leave them outside to freeze. When frozen, you pop the balloon, which leaves you with a rounded blob of colored ice, which you then arrange in an artful and decorative pattern.

So it's basically a technique for making your own temporary, winter-only gazing globes, I guess. Kinda.


Mine didn't turn out as intended. I had set them down on the ground in the back yard to freeze, next to one another, and although it got very cold on the night in question, they apparently managed to insulate one another well enough that only the tops froze: the bottoms stayed liquid.


This left me with a bunch of pastel, bowl-shaped pieces of ice, instead of the solid, brightly-colored spheroids I had been envisioning. Also disappointing: the balloons, when popped, immediately gushed water. I was trying to be careful, but I still managed to soak a glove while I was doing this, which was uncomfortable and inconvenient. A wet glove sticks to ice in sub-zero temperatures much the same way a wet tongue sticks to a metal pole, it turns out.


However, there was one good side to this: the colors, disappointingly pastel though they were, were at least all more or less equally pastel, so they still looked like they more or less went together, and the inverted-bowl shape reflected light interestingly, giving them a more metallic kind of look than they would otherwise have had.


It would have helped if there had been less snow on the ground when I did this, since from a distance, they kind of disappeared under the snow around them (which is why I didn't post any pictures of them from far away). But these are all lessons I can apply to next time. (Yes, I am planning a next time.) And I at least got one cool-looking photo out of it:


Oh! And! I also, in the process, managed to ruin one perfectly good laundry basket. It turns out that the maximum carrying capacity of a chilled plastic laundry basket is exactly five water-filled balloons. Tempting though it might be, don't add that sixth one: the basket handles will break on you, sending five water-filled balloons skittering around the plant room. The sixth will, of course, land on your white tennis shoes and burst, both soaking them and turning them lavender.

Picture: Ladybug on Jade Cuttings

I am having a very bad day yesterday, and as a result, I respectfully request that readers supply their own commentary for this post.

(It's nothing to worry about. I'll likely be fine by the time you read this.)

-

UPDATE: I in fact am fine. Disruptions in my sleep schedule are highly correlated to flare-ups of the ol' depression, and such a disruption happened yesterday morning.

Unfortunately, knowing that there is no rational basis for the way I'm feeling, and that it's all just a matter of me having gotten up too early, does absolutely nothing to blunt the unpleasantness. So I just have to ride it out for the 6-12 hours it lasts.

The good news is that my brain is extraordinarily predictable about the whole business, and there are certain subjects I only think about during these depressive episodes (Mostly prior employers and how badly we failed and disappointed one another, especially a job four jobs ago which I left in 2004 under traumatic and confusing circumstances.), which makes it much easier to identify what's going on and withdraw from the world until the storm has passed. Though experience is teaching me that I should be withdrawing much, much more thoroughly from Twitter when this is happening than I have so far been able to do. Something about how people are on Twitter really pushes my buttons sometimes.

Pretty picture: Hyacinthus orientalis cv.

This is an old picture, but I don't know how old exactly: it was taken at some point while I was working at the greenhouse, and judging from the amount of blurring, it looks like it was probably taken before I figured out how to use the macro feature, so it might be from my first spring there, almost two years ago now. This is, unfortunately, all you get today, because I severely overestimated my interest in / tolerance for blog maintenance yesterday, and consequently found myself with no time to write.

Also, there's kind of a problem with me not having much in the way of current pictures to post about: nothing much seems to be happening here that I haven't covered already, and when I went to the ex-job to get pretty-picture blog fodder, I discovered them closed, for three consecutive days (Jan 1-3), which is unprecedented and actually concerns me a bit. I don't remember ever being closed for more than one day at a time when I worked there. Perhaps they needed me giving back half my paychecks more than they let on at the time.

So I don't know what I'm going to do for future posts, but I'm sure I'll come up with something. It may end up involving some hurried finishing of long-abandoned old posts. We will see.

Chuck Cunningham (Pandanus veitchii and P. utilis)

During the first season of the TV sitcom "Happy Days," Howard and Marion Cunningham had three children: Chuck, Richie, and Joanie. Now, you probably know Richie (Ron Howard), and you're probably familiar with Joanie (Erin Moran), but Chuck (played by two different actors, Gavan O’Herlihy and Randolph Roberts, which couldn't have helped) may be news to some.

The story was that Chuck was the oldest, and played basketball at the University of Wisconsin-Milwaukee. His contribution to the show was, I'm told, mainly brief appearances on the way to or from basketball practice: the writers didn't know what to do with him beyond that. At the beginning of the second season, he was written out of the show with the explanation that he was going to college (though he had already been going to college), and he was never seen or mentioned again. Subsequent episodes had Howard and/or Marion saying explicitly that they only had two children.

The "Happy Days" cast. Chuck (Gavan O’Herlihy? Probably?) is in the upper right corner.
This sort of thing has happened in a surprisingly large number of shows,¹ often enough to be given its own name, "Chuck Cunningham syndrome." It's really kind of an odd thing to have happen: I can see the occasional need to drop an actor, but if they just vanish without explanation and are never mentioned again, it seems like the writers have failed at some point along the way. Maybe it's more complicated than that. Anyway. My point in bringing this up is that CCS happens to houseplants sometimes as well.

A variegated Pandanus veitchii, better known to PATSP readers as the Big Damn Screw Pine, or BDSP.
I've probably seen more pictures of screw pines in houseplant books than I have individual plants for sale. I can say this about other plants too,² of course. But it stands out with Pandanus, because so many books and websites mention them in part to say they're awesome houseplants. I found one site that actually called Pandanus "the best houseplant there is."³ I don't know if they used to be widely available and then disappeared, or if they were always rare, but it's weird that a plant that is as dramatic, and easy to grow as this isn't seen at least occasionally in the stores.

I got most of my plants from my ex-job, which is also the only place I've ever seen them for sale; a few others came to me by trade. Screw pines never sold that well at work, of course; in the whole year and a half I was there, we only sold one plant to a regular customer, a very large non-variegated P. veitchii which had been there for at least a couple years by the time it sold. Perhaps that answers my question about why we don't see more of them: maybe when stores do bother to get them in, they don't sell.

And I don't blame the customers. Screw pines are kind of mean. Both P. utilis and P. veitchii have three rows of hooked, sharp spines running the length of the leaves, one on each side of the leaf and then another on the underside along the midrib. The spines are pointed outward, so reaching in toward the center of the plant means you're going to get scratched, however careful you try to be. Worse, the scratches tend to hurt and itch longer than ordinary scratches. I found rumors on-line that this might be because the spines contain calcium oxalate crystals, but was unable to verify.⁴ They also cause the occasional allergic reaction, but I don't know how common this is, or how serious it is when it does happen.

So they're unpleasant to get close to. But even so, this is hardly a reason to disappear the whole genus from sale. Yucca guatemalensis have serrated leaf margins; some Aechmea and Neoregelia cultivars have marginal spines very much like Pandanus but sharper; Pachypodium lamerei's trunk is spines from bottom to top; all kinds of Agave species are sharp and pointy; nearly the entire Cactaceae family is covered in spines; and a solid percentage of Euphorbias are both pointy and toxic. And everybody still sells all of them. So why wouldn't customers buy Pandanus? I honestly have no idea. Perhaps, like the "Happy Days" writers, they just don't know what to do with them.

Anyway. Pandanus is a big genus (500-1000 species⁵), a few dozen species of which are economically significant. Only two (utilis and veitchii) are common as houseplants, though other species are cultivated in other contexts.

Pandanus amaryllifolius, or "pandan," in cultivation. Photo by dekoelie at Wikimedia Commons.
For example: P. amaryllifolius,⁶ known as "pandan," is used throughout Southeast Asia as a flavoring agent in cooking (see the post by Autumn Belle about its uses in Malaysia specifically; it's also used elsewhere).⁷ The leaves are not eaten on their own, but juice from them may be added to a dish, or they may be baked with rolls or cooked with meat to release the flavor, and then discarded. Everybody goes on and on about how great it smells (e.g. here and here), though the descriptions are vague enough that I don't get a very clear idea of what it's like. "Sweet" and "vanilla" seem to pretty much cover it. I don't know if it'd be growable as a houseplant or not, but it sounds like an intriguing plant, and I'd like to try.⁸

See? I told you there would be cake. Cake made with pandan (Pandanus amaryllifolius) juice as flavoring (and coloring?). Photo by Glenn G, via Wikimedia Commons.
Other Pandanus species of interest, which have all been cultivated as houseplants and ornamentals to some degree or another, include the more thoroughly hostile P. candelabrum, which has spines pointing both inward and outward, the small P. graminifolius, which maxes out at 2-3 feet (0.6-0.9 m), and the pretty but apparently delicate P. heterocarpus/ornatus. P. reflexa, which resembles some of your angrier Aloes, is particularly striking, though just looking at P. reflexa is enough to tell you why it never really caught on as a houseplant. Pictures of all these, plus a few others, can be found here.

The geographic origin of screw pines is difficult to pin down, because they've been introduced all over the place, often quite a while ago. P. tectorius is common in Hawaii, for example, but different websites give different answers about whether or not it's a native Hawaiian plant.⁹ Other species are found in islands of the South Pacific, Madagascar, Africa, the Philippines, Australia, and throughout tropical Asia. Whether any of them are originally from these places is beyond my ability to determine. There seems to be some consensus that P. veitchii is from Madagascar.

Wherever they started out, some screw pines are highly useful plants, so it makes sense that explorers would have brought a few plants along with them to plant elsewhere. In fact, P. utilis is so useful as a source of fiber for ropes, nets, baskets, paper, roof thatching, etc., that its botanical name means "useful."

View from the top of the BDSP, looking into the rosette. The leaves of P. veitchii don't really spiral in the same way that P. utilis does.
Speaking of names: "screw pine" comes from the plant's appearance, particularly that of P. utilis. The "screw" part of the name is because each new leaf emerges slightly to the right of the previous one, with the result that the leaves form a spiral as the plant ages.¹⁰ With P. utilis, the leaf scars on the plant's initial stem also have a spiralling pattern to them, though this stops when the plant begins to branch. The "pine" part comes from the fruits, which have woody seeds in clusters, somewhat resembling a large pineapple or pine cone though I don't see the resemblance so much myself.

Fruit on P. utilis. For the seeds, imagine the same thing, but the color and texture of old wood, and split into individual pieces instead of all attached to one another like this. Photo by B navez, via Wikimedia Commons.
Since we're primarily concerned with Pandanus as a houseplant, I won't share all of the interesting stuff I found out about them as landscape plants, but I will note that both veitchii and utilis are capable of getting very large, though none of my sources agreed on a maximum size. Plants 25 feet (7.6 m) tall, and equally wide, seem to be fairly typical, though I ran into claims of 60 feet (18 m) tall for utilis. It is even recommended that they be planted no closer than fifteen feet (4.6 m) from sidewalks, unless you don't mind the sidewalk becoming un-navigable, because the plants get wide about as fast as they get tall. This is also true indoors, though it doesn't happen nearly as fast.

The flowering and fruiting are another potential problem in cultivation; I found more than one source that said veitchii never flowers or fruits. This could well be true -- it's not like I found pictures of veitchii fruits or flowers -- but it just cries out for an explanation of some kind, and nobody but me seems to find the question interesting. Utilis, on the other hand, flowers and fruits quite freely once mature, and can produce hundreds of clusters of fruit at the end of the summer, each of which may weigh eight pounds (3.6 kg). Though the fruit may be left where it falls, it attracts fruit flies and squirrels, as well as other pests,¹¹ and the seeds sprout easily. So if you fail to pick up the fruits promptly, you may end up with a plague of vermin, followed by a plague of seedlings to pull up.

P. utilis plants are always either male or female, with only female plants producing fruit, but the female plants are, surprisingly, considered more desirable for landscapes. The explanation most sites give is that the fruits, while a pain to get rid of,¹² are also pretty, or at least interesting, and the visual appeal of the fruits outweighs the hassle of cleaning them up. I've seen pictures of trees with full crops of fruit (e.g.), and frankly, I don't think they're so cool as to be worth picking up hundreds of pounds of fruit every year. Different strokes, I suppose. The male plants have long, fluffy, tail-like flowers, which are fragrant if short-lived, and that sounds like a much better deal to me.

Male flowers on a Pandanus utilis. I couldn't find any pictures I liked of the female flowers. Photo by B navez, via Wikimedia Commons.
Both veitchii and utilis will branch with age, forming multiple heads. I don't know whether this happens with indoor plants. I suppose if one lives long enough, it would have to branch eventually. Utilis is prone to develop a triangular crown over time (e.g.); I'm unclear about whether veitchii does this too. Both will, after a certain age, begin to drop leaves at a steady rate of about 10-15 per day, which are of course still spiny and sharp and need to be picked up all the time, lest they smother lawns, provide shelter for rodents, injure people, or rob a 7-11.

Mature, branched specimen of Pansanus utilis. Photo by KENPEI, via Wikimedia Commons.
Pandanus spp. are very salt-tolerant and relatively pest-free, so aside from having to clean up after them and plan carefully when planting them, they don't appear to require a lot of thought. They are also, according to davesgarden.com commenter IslandJim, traffic-stoppingly gorgeous when mature, and a large specimen may sell for $5,000 to $10,000 U.S. One possible down side is that screw pines can harbor, and be killed by, a bacterium "lethal yellowing," an extremely contagious and fatal plant disease which is spread by the leafhopper Myndus crudus.¹³ Outdoor plants also sometimes develop black spots on the leaves. There's no solid consensus on why the spotting happens,¹⁴ but removal of the affected leaves appears to be the best cure.

As a houseplant, a lot of this is irrelevant: your plant is unlikely to be affected by lethal yellowing, it's not going to fruit or drop a lot of leaves, and it will probably not get twenty-five feet wide, either, unless you have a very large plant room. But like the old proverb says, you never know when you might be visiting Florida and need to identify a screw pine in somebody's yard.

My personal screw pines are all P. veitchii. I want to get a utilis at some point, and like I said above, I'm looking for an amaryllifolius too, but for the moment, I just have the ten veitchii. The main differences between veitchii and utilis are as follows: veitchii is available in plain green or variegated forms (yellow-white margins with a green center). The spiral leaf arrangement is present with utilis but not veitchii, and the marginal spines on utilis are red.¹⁵

Ginormous stilt roots on P. utilis. Photo by Pandano at Wikimedia Commons.
Both indoor and outdoor plants will grow stilt roots (sometimes called "prop roots"). I'm not quite clear on how it works, but it would seem that stilt roots are better at bracing a plant against winds in sandy soil than more "normal," underground spreading roots do. On outdoor plants, aerial roots can get to be three inches (8 cm) in diameter. Rather than growing aerial roots that grow downward until they meet soil, like Monstera deliciosa, Pandanus spp. grow their roots below the soil first and then push themselves up out of the ground. This is a little freaky, but it's how it's supposed to be, so try to appreciate them. Nothing but frustration will result from trying to re-bury your plant's roots, though I suppose if you've got a lot of peroxide and band-aids you're desperate to get rid of, this would be a way to solve that problem.

Stilt roots beginning to form on a very young P. veitchii.
They'll also, unsurprisingly, try to get big indoors, sometimes fairly rapidly. I was surprised, for example, at how quickly the BDSP has grown, in just the two years we've known one another. It's not the blinding speed of an Ardisia elliptica or anything, but if the BDSP continues at this rate, it's going to need its own room within four or five years. Which I both want to happen and do not want to happen.

The BDSP shortly after we first met, in October 2007.
But anyway. It's not at all difficult to keep Pandanus indoors, except for the size and spines.
LIGHT: Give them as much sun as you can manage. Some of my plants have had to go without direct sunlight for a season here and there, and it didn't appear to cause any lasting harm, but only do this if you have to, since I'm sure mine resent it and will make me pay for it later.

WATER: Water is one of the least problematic aspects of care. If allowed to get too dry, leaf tips will burn, and too much water will (allegedly¹⁶) lead to rot, but I think most people are already predisposed to water indoor Pandanus more or less appropriately. My own plants are kept on the dry side, and consequently get dry leaf tips occasionally. When it gets really bad, I take brown tips as a sign that the plant needs to be moved up to a larger pot. When I do, it's usually followed by a burst of new growth.

TEMPERATURE: Most everything I've seen says that Pandanus shouldn't get colder than 55F/13C, which is weird, because if grown outdoors, they are supposedly hardy to 30F/-1C.¹⁷ So I question this no-colder-than-55 stuff, because I'm fairly sure that the BDSP didn't come inside this fall until temperatures were at least in the 40s (F; which equals 4-9C), possibly colder. And it was fine, as far as I can tell. On the other hand, some of the BDSP's leaves have browned recently, possibly from being up against the windows in the plant room (which is kind of unavoidable). I don't know how cold that actually gets, though. So, bottom line, keep your plant above 55F/13C as much as possible, but don't panic if it gets colder.

HUMIDITY: Here's another case of conflicting advice and experience. Almost every source I've seen, whether on- or off-line, says that Pandanus spp. need high humidity in order to do well. It has not been my experience that air moisture is that critical, even taking into account that I have higher indoor humidity than most people.¹⁸ Your results may vary.

PESTS: Outdoor plants can get scale (here is proof), but for all intents and purposes, there are no serious pests of Pandanus when kept as houseplants.

Close-up of the base of the BDSP, showing the developing trunk in the center and the many, many, developing stilt roots and offsets around it.
PROPAGATION: P. veitchii forms plantlets as it grows, sort of around the base of the main plant's leaves. This begins when they reach a certain age, and as far as I can tell continues ever afterward. Except for the first step, propagation from plantlets is extremely easy: you reach into the center of the plant, grab a plantlet firmly and pull it away from the plant, and then stick it in dirt. Plantlets will usually (always?) have at least one root already formed, so then it's just a matter of waiting for it to recover enough to produce new growth. To the best of my recollection, every plantlet I've tried to propagate has worked.

P. utilis does not form plantlets. It can be propagated from stem cuttings, technically, though if you cut off a growing tip, the plant will not sprout a new one to replace it: the branch will just sit there, being a stump, forever after. So this is something to try only with older, already-branched plants, and then only if you don't mind leaving a leafless stump on the older plant.

And there are easier ways. More commonly, P. utilis is propagated from the abundant seeds. I tried this once, with seeds from seedman.com, and it didn't work at all, but I think this is probably my fault for not keeping them moist enough, and for giving up on the process too early. One is supposed to soak the seeds in warm water for at least 24 hours, and possibly as long as five days, then plant in a moist medium (like maybe vermiculite or finely chopped sphagnum moss), keep warm and moist, and then wait for two to three months. I have no idea how easy this is when done correctly, but if the seeds are willing to sprout all over people's yards, I'm thinking they must have a pretty strong will to live.

GROOMING: The BDSP has occasionally dropped some leaves, and pulling those off is never fun. The younger plants of mine haven't really needed any serious grooming at all, and drop leaves only very rarely.

One of the stranger things I've seen with P. veitchii is that from time to time, new leaves will come in yellow instead of green. This happens on both plain-green and variegated plants. Sometimes the new leaves are solid yellow; sometimes they begin yellow and then turn green later; and sometimes the tip is yellow and the base is green. I saw one site attribute this to the season, and it does appear to happen more during the winter than the summer, but my personal inclination is to blame this on nutritional deficiencies, because it seems to stop briefly when I give them fertilizer. I haven't made a dedicated study of the problem, though, so I'm not sure it's nutritional. Whatever is going on, it doesn't seem to hurt the plants any: they keep producing leaves of the same size, at the same rate, and sooner or later, the yellow leaves turn green regardless. So it's not really a problem, but it's weird.

See? Some leaves one color, some leaves another color, some half-and-half. WTF, Chuck?
The BDSP, toward the end of the summer, and then for a little while after I brought it inside, was doing a thing where the newest leaves were staying attached to one another, turning the growing tip into a hard, spear-like point. I physically pulled them apart from one another a couple times (ripping a few leaves slightly in the process), and eventually it got over this, whatever it was, but I never figured out a cause. Possibly humidity or temperature. Really no way to tell. I wish I'd thought to get pictures.

The potentially enormous size of the plant means it's not for everybody. The growth rate appears to be constrainable by pot size, to a point, and plantlets tend to be very slow to get going, but in the long run, you need to plan for a screw pine or you will be sorry.¹⁹ Once they decide it's time to get big, there's no stopping them. I've had offsets barely grow at all for a year and then suddenly quadruple in size in a few months.

The BDSP in July 2009.
FEEDING: Nobody has any specific advice on feeding, from what I've been able to find, and especially nothing that would be applicable to indoor growing, so this is kind of a guess, but since feeding seems to resolve the yellow-leaf issues sometimes, it's a fast-growing plant, and it's fairly salt-resistant, you maybe don't have to use quite as much restraint with Pandanus as with some other houseplants. I'm not sure what too much fertilizer looks like, with these, so start slow and increase as you feel the need to increase.

I was really hoping that by the time I reached the end of the profile, I'd have found an explanation for screw pines' absence from the stores despite their prevalence in the houseplant books. I mean, there's nothing ambiguous about "the best houseplant there is," right?²⁰ I found other people wondering the same thing, but nobody seemed to have any answers. Perhaps they were never that common to begin with. Perhaps they just don't sell well enough to be worth the pain and effort of producing them. Perhaps they're attending college. I welcome other theories, if anybody has some.

References in no particular order:
Autumn Belle's post about cooking with pandan
another blog post about cooking with pandan, this time from a cooking blog
plantcare.com
apartment-gardening-homes.com
plantideas.com
chestofbooks.com/gardening-horticulture (Extremely interesting; highly recommended)
denverplants.com
davesgarden.com for P. veitchii
davesgarden.com for P. utilis
houseplantgrowing.com
Wikipedia for "Pandanus"
Wikipedia for "Pandanus utilis"
floridata.com
arhomeandgarden.org
mgonline.com
desert-tropicals.com
edis.ifas.ufl.edu

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Photo credits: Mine except 1) where otherwise noted and 2) the "Happy Days" cast picture, which I don't remember the source of and apparently didn't bother to write down.

¹ Various breakdowns can be found at Wikipedia, fact-archive.com and tvtropes.org.)
² Billbergia nutans, for example: I've never seen one for sale, but they're in a lot of the books. (Also on a lot of the websites, which causes me a certain amount of jealousy.) I don't think I've ever seen Cissus antarctica, Howea forsteriana, or Asplenium bulbiferum for sale, either. With Howea, I know why: they're hella expensive (even wholesale), but the others all seem like something I should have run into at least once, or at the very least should have seen on the availability lists at work.
³ (Doubtful. I like Pandanus a lot more than most people do (or could), but I wouldn't go that far. Probably not even in my top 20: there's a lot of competition. Top 50, probably, though.)
⁴ I can verify that at least some Pandanus species contain some calcium oxalate crystals somewhere within the leaves. Whether P. utilis or P. veitchii do, and whether this is the reason for why the wounds inflicted by Pandanus leaves tend to itch for a long time, I couldn't say. But it seems like a reasonable theory. This also probably means that the leaves are unpleasant to chew when raw, as with other plants that contain calcium oxalate crystals (for example: Philodendron hederaceum, Schefflera actinophylla), though I didn't see any websites address their toxicity to pets or children directly.
⁵ Wikiposedly. I was unable to confirm this, either. Quite a few Pandanus species seem to have multiple botanical names, too, which makes it all that much more confusing.
⁶ This is the same plant called P. amaryllis. I'm going with amaryllifolius because 1) that's what Autumn Belle and davesgarden.com, as well as other reputable sources, use, and 2) it avoids confusion with the genus Amaryllis.
⁷ "Pandan" is said to be the native name for Pandanus species in general, and is the origin of the botanical name (plus an "-us" to make it sound properly Latin). I get the impression from reading Autumn Belle's post that if you're in Southeast Asia and you say you want pandan, P. amaryllifolius is what people are going to try to give you, even though other Pandanus spp. are probably also called "pandan." If you want to get specific about it, Autumn Belle says to ask for "pandan wangi," which distinguishes it from the other pandans.
⁸ The husband and I did wander in and out of all the Asian markets we could think of in Iowa City a while back, when I started writing this profile, which took most of an afternoon and wound up being useless: nobody had any rootable cuttings, nor any fresh leaves to smell, nor even any dried leaves, nor products flavored with pandan. Nor had anybody even heard of it, on the occasions when I tried asking somebody. One person tried pointing me to coriander, which . . . well, either this was a language barrier, or they were just throwing something out there at random to see if I'd go for it. Seemed more like a language problem.
This was very frustrating, though it's possibly not fair to expect stores to carry the product on the off chance that one guy in Eastern Iowa happens to hear of it and want to buy some. I will continue to try, but it looks like probably if I want pandan I will have to order a plant from Hawaii, Florida, or someplace like that. I did find a place that sold it from Florida, and I hope I still have the site bookmarked somewhere.
⁹ I think the people saying it was introduced probably have the better case, but that's just me. Native Hawaiians appear to be happy to claim it as a native, though they're relative newcomers themselves, on an evolutionary/geological timescale.
¹⁰ The arrangement of leaves is completely different in P. veitchii. Though the name "screw pine" is used for all Pandanus species as far as I know, the actual shape of the plants varies somewhat.
¹¹ Some Pandanus spp. are said to produce edible fruits, or at least fruits which are edible if cooked first, but as best as I can tell from the conflicting information I've seen, utilis fruit is either outright inedible or is edible but not very tasty.
¹² It's apparently possible, with a sufficiently large plant and a sufficiently dedicated gardener, to collect enough fruit to fill several garbage cans every day for several days.
¹³ Lethal yellowing is technically a "phytoplasma," which is not a virus but a bacterium, but for some reason people like to call it a virus on-line anyway. I don't know how that got started, or why it persists. Lethal yellowing affects some species of palms, including houseplant species like date palms (Phoenix), coconut palms (Cocos nucifera), and possibly the panama hat palm (Carludovica; unfortunately, the plant typically sold as Carludovica is, I think, more probably an Asplundia, and I'm not sure which genus is susceptible to lethal yellowing, or whether either is.), and can wipe out susceptible species in a given area very rapidly. Everybody makes lethal yellowing sound pretty dire; I don't know how widespread or dangerous it actually is. Possibly anything with "lethal" in its name is going to sound dire (e.g. lethal rainbows, lethal kittens, lethal cupcakes). Treatment is possible, but involves injecting antibiotics directly into trees, over long periods of time, and looks expensive.
¹⁴ One school of thought is that it's a normal leaf reaction to cold, wet conditions, possibly a fungus; the other main theory is that it's caused by insects burrowing into the leaves. The second option makes more intuitive sense to me (at the very least it seems like it would be more easily disproven, if wrong, so the fact that people are repeating it suggests that it's not been disproven and is therefore probably right), but I've not seen this problem in person, nor even any pictures of it on-line, so that's entirely based on my gut, and the reader should be warned that my gut is frequently wrong, which is why I try to think with my brain as much as possible.
¹⁵ The red-spine thing is possibly not true for plants grown in inadequate light. Also, one davesgarden.com commenter mentions a variegated Pandanus in the comments for P. utilis, but I think they are probably thinking instead of veitchii or baptistii or some other species, as his/r comment is the only time I saw anybody mention a variegated utilis.
¹⁶ I haven't seen this myself.
¹⁷ (One source said they didn't tolerate dry heat or temperatures below 30C well. 30C is the equivalent of 86F, which makes no sense. I assume they meant 30F.)
¹⁸ Because of all the plants I have, and the terrarium, and the aquarium in the basement, and the small pans of water in front of some of the heat vents. We in fact have a slight issue with water condensing inside the roof, which the husband informs me can turn into quite a bad thing. I've discussed this with the plants, and they are unwilling to accept lower humidity levels in exchange for a roof that stays intact and doesn't grow mold. Even after I explained that this isn't really in their long-term self-interest, they still maintain that they'd rather have high humidity now than a roof later. Which now that I think about it is kind of insulting: clearly some of them don't think they're still going to be here very long.
¹⁹ Actually, you may be sorry whether you plan or not. Getting your arms and/or face all scratched up on a regular basis gets old.
²⁰ Of course, for all we know, he's heavily sedated now, and in an institution for the criminally insane. I mean, there's no reason to take that one guy's word for it unquestioningly.