Mannequin: Plasticum, Metallum and Sericum spp.

Plasticum, Metallum and Sericum are the only three genera in the small plant family Artificaceae. The precise number of species is uncertain, but some common ones are:

Plasticum ficusoides (plastic ficus)
Plasticum hederaceum (artificial ivy)
Plasticum marantoides (maranta-leaved plastic plant)
Plasticum hostaformis (hosta-leaved plastic plant)
Plasticum dracaenae (plastic dracaena)
Plasticum pseudophalaenopsis (false phalaenopsis)
Plasticum metallivenosa (wire-veined plastic plant; wireweed)
Plasticum officinalis (plasticwort)
Plasticum walmartiensis (Wal-Mart plastic plant)
Metallum aglaophylla (Christmas tree)
Sericum artificialis (silk plant).

Plasticum ficusoides var. binnendijkii
Some of the difficulty in getting a precise count on the number of Plasticum species is because taxonomists differ on where to draw the lines between them, with the most extreme of the "splitters" recognizing hundreds of species, subspecies, and cultivars, while the most extreme of the "lumpers" consider the Artificaceae to contain three and only three species, Sericum artificialis, Metallum aglaophylla and Plasticum artificialis. I think the lumpers have more of a case, personally, but since the lumpers merely push off the precise identifications to the subspecies level,¹ it's more convenient for me to follow the lead of the splitters here. It doesn't matter a whole lot either way.

All Plasticum cvv., and at least some of the Sericum cvv., share a few fairly distinctive characteristics which make them easy to identify. For one thing, many of them have leaves with a fibrous or fuzzy margin, as if the leaf veins continued slightly beyond the edge of the leaf, which is best illustrated here:

The leaf fringe in question is most visible on the frontmost leaf of this Plasticum cordylinis, though you may have to open the picture in a separate window to see it clearly.
The second odd adaptation is that, although they generally have the same sort of coloration as other plants, their venation often doesn't actually follow the color, and is instead composed of two sets of very regularly-spaced veins oriented at right angles to one another, as seen here:

Close-up view of a Plasticum marantoides (also called Plasticum artificialis marantoides, elsewhere on PATSP).
Third, there is often an odd smell from all portions of the plant, which has been likened to a chemical / new-car kind of smell, and which either disappears over time or one eventually gets used to it. It tends not to be overpowering in most cases, though in a small room with poor ventilation, I suppose it could build up to offensive levels.

Plasticum ficusoides var. benjamina, with a smaller Plasticum pseudocactus in the lower right.
Plasticum is primarily grown for cut flowers, which are very long-lasting (even surviving well if their vase goes dry!) and occur in a wide range of colors, including chartreuse, green and turquoise (colors which are rare in most other plant families). Though Metallum aglaophylla has been used indoors during the holiday season since the mid-twentieth century, other species in the Artificaceae have been adopted more slowly for indoor use. Plants bought in bloom will usually hang on to their flowers for years -- seriously, they make Anthuriums and orchids, whose blooms may last three months tops, look like pikers -- but it's next to impossible to induce blooming.

Care for Plasticum is simple but quirky:

WATERING: This is one exception to my general rule of always watering plants thoroughly, so the root ball becomes completely saturated with water. Although such watering usually doesn't seem to affect the plant any, it does often speed up the breakdown of the soil (which is often rock-solid and/or water-repellent), with plants in the Artificaceae. Plasticum and Sericum are very drought-tolerant, so water only when you're positive the plant needs it, and then only in tiny amounts.

LIGHT: Do not put Plasticum in direct sunlight, even filtered sunlight: the leaves will sunburn, leading to bleached or discolored spots. As growth is extremely slow, and bleaching is permanent, you will have to live with a bleached plant for a very long time before new growth occurs to replace the old. Plasticum and Sericum thrive in low-light areas, however. A surprisingly large number of people literally keep theirs (particularly M. aglaophylla) in closets and other dark storage areas, apparently without harm, for months at a time, though I can't endorse this.

Plasticum perforatum.
HUMIDITY: None of these plants seem to be particularly affected by humidity levels either way. These are good choices for spots where humidity is always low, or in climates which are frequently very dry.

TEMPERATURE: All known Artificaceae species are hardy in all USDA zones, though in extreme heat (indoors or out), Plasticum sometimes develop a weeping or "melted" habit, which most people consider unattractive. Any indoor temperature which is comfortable for you should also be comfortable for them, though.

PESTS: Plasticum is one of the most insect-resistant plants known. Sericum may be attacked in certain cases, but this is rare. Mildew will occasionally attack plants kept in extremely moist spots over long periods, though this seems to be uncommon.

Variegated Plasticum hederaceum.
GROOMING: Virtually non-existent, though on occasion growing tips will simply fall off of the plant. These can usually be stuck back into the trunk or branch where they originated, and will graft themselves back again. (One can also try to propagate them. Read on:)

PROPAGATION: I have consistently been unable to get Plasticum to root, even after months in constantly-moist vermiculite and in a humidity tent. Rooting hormone doesn't seem to help either. On the other hand, I still have hope, because they're not actually browning and dying either. I'm more than interested if anybody has tips. Berries and seed pods are occasionally seen on mature plants, but when opened, these often completely lack seeds, and when they do contain seeds, the seeds are non-viable. I could not find any information on how these plants are propagated by growers.

FEEDING: All members of the Artificaceae have extremely minimal requirements for nutrients and will do best if not fed. Overfeeding will often cause a green or blue discoloration of leaves and/or stems, which may be permanent.

Aside from the difficulty encountered in propagation, their slight susceptibility to overwatering, and their intolerance of extreme heat, they're about as carefree as one can get.

Their toxicity to pets and children appears to be fairly low but not zero. Some varieties may contain small amounts of toxins, especially those grown in China (as for example P. walmartensis, which is native to China: virtually all of it is still cultivated there). In most cases, though, the problem is that the partly-chewed leaves can bridge across gaps in the respiratory or digestive systems, leading to choking, asphyxiation, bowel obstruction and abdominal pain, so it's probably a good idea to keep them away from kids and pets. They are also frequently flammable (rare for living plants), which makes them something of a risky prospect for certain locations (e.g. on either side of a fireplace, though realistically you shouldn't be trying to put any kind of plant on either side of a fireplace if you ever intend to use the fireplace). Fire-resistant cultivars exist but are difficult to find.

Not all nurseries carry these plants (and some other stores carry no plants except these, which is weirder). We had some where I used to work, but I've never tried to grow one at home: I just don't like them, when it comes down to it. Their growth habit never appears entirely natural to me, somehow: on the treelike forms, the foliage is gappy, with very dense and very sparse areas, the main trunk isn't in proportion with the side branches, and the whole thing is just strange.

* * * At this point, I'll drop the conceit that I'm talking about a real plant, and just explain to you why artificial plants bug me, by referring to a concept called the Uncanny Valley. * * *

I usually don't mind odd-looking plants. In fact, usually, I really like odd-looking plants. But artificial ones are somehow odd in all the wrong ways, or not quite odd enough, or something. The term uncanny valley, which is a term from robotics and computer graphics, refers to how relatable or pleasant people find representations of human beings (robot, image, computer graphic, statue) according to how realistic they are: if you start out with a very abstract image and gradually make it look more and more human, it will be more and more appealing and human-like as you add details up to a certain point. At that point, adding more detail and accuracy will just make your robot, avatar, or whatever, look increasingly creepy, which will only be overcome by extreme verisimilitude and the creation of a nearly-perfect replica of a person.

Photo by Michael Möller. Found in the Wikipedia entry for Mannequin.
Think of the progression from a circle (very abstract) to a smiley face (still abstract, but more human) to Homer Simpson (abstract, but recognizably a human being) to department store mannequin (more detailed human being) to ventriloquist's dummy (creepy, unnerving) to wax sculpture (also unnerving) to photograph of an actual person (perfect detailing). The ventriloquist's dummy / wax-sculpture area is what we're talking about with the uncanny valley, as it applies to people.

This also likely explains why, as a child, though I liked Mister Roger's Neighborhood's puppetry in the Neighborhood of Make-Believe, I found (and still find) Lady Elaine Fairchilde icky and off-putting. Daniel Striped Tiger and Henrietta Pussycat are clearly animals, X the Owl is cartoony, King Friday XIII is personlike but his face is mostly covered by a beard, but Lady Elaine Fairchilde has weird, big, narrow eyes, strangely-colored cheeks and nose, which nose is extremely long and pointy: she's got characteristics of a person, but it's just not quite right somehow:


It doesn't help the creepiness factor that she only has one facial expression, is occasionally genuinely malicious, and talks without moving her mouth. Though if I remember correctly, none of the puppets in the Neighborhood of Make-Believe moved their mouths when they talked so maybe it's not fair to single her out on that last point.²

The uncanny valley is also, by the way, posited as one explanation for why we're scared of certain kinds of "monsters," like Frankenstein's monster, zombies, mummies, aliens, clowns, that goddamn Burger King mascot may he rot in hell,³ and so forth: they have a lot of the details, proportions and postures of a real person, but they're also noticeably different in certain ways: missing or wildly exaggerated body parts (especially noses: aliens don't have them at all, clowns have huge, brightly colored ones), odd movement (Frankenstein, zombies), weird skin color (Frankenstein, zombies, aliens), etc. The reason these are thought to be creepy and off-putting is because off-colored skin, weird posture or facial expression, etc., are also qualities of corpses (or at least corpses prior to the funeral industry and embalming), and there are very good evolutionary reasons for avoiding corpses. (If the person was killed by a wild animal, the animal might still be nearby and kill you too; if s/he was killed by disease, you might catch it, etc.) Hence, ookiness and monsters.⁴

A couple fairly realistic mannequins (though the fact that they're chained to a pipe at the neck kind of makes it obvious that they're not people). Uncredited photo from Wikipedia, found in the entry for Mannequin.
I don't know that this theory is provable exactly (though I like it, or else I wouldn't have brought it up), but you do see the general idea: very much like people, but wrong is way creepier than not very much like people at all.⁵

My point in bringing all this up (and see also these links, for more about the Uncanny Valley as it relates to human representations: arclight.net, Wikipedia, slate.com; it might also be worth your time to do a Google image search for "uncanny valley:" there are good example pictures out there that I didn't use because I didn't think they were probably public domain) is that this is more or less also my reaction to artificial plants: they look very plantlike, up to a point, but the mimicry is never all that great, and to me they wind up looking undead, ill, and wrong.

Because of this, I really want to condemn artificial plants and anyone who buys them, because they are creepy and weird and I don't want to have to see them. But I recognize at the same time that my dislike of artificial plants, intense though it may be, is still only a matter of taste, and it would be way past absurd for me to pretend like owning one is some kind of grave moral failing.

So I will just say that yes, plastic plants are out there, and in some circumstances they're fine,⁶ and in the rest of the circumstances they are also fine.⁷ However. They also don't really give you the natural look you're going for, they'll dirty your air instead of cleaning it,⁸ and, worst of all, they will never, ever love you like a real plant will. So choose wisely.

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¹ (So one winds up with things like "Plasticum artificialis ficusoides," and "Sericum artificialis cordylinis 'Burgundy,'" which take much more work to type but don't do any better job of identifying anything.)
² There are other schools of thought on Lady Elaine, ranging from identification (This post's author wonders "if this [description of Lady Elaine] could describe me more.") to envy (I found a Flickr photo captioned "sometimes I wish I was an alcoholic hand puppet with magical powers living in a rotating museum.") to open admiration (This post's author "may have to start a chapter of the Society for the Appreciation of Lady Elaine Fairchilde.").
I'm not the only person to find her creepy and unpleasant, though, despite her unexpectedly large fan base. ("Did FRED ROGERS purposely pick a puppet design to scare children into his submission?" "I was completely terrified by lady elaine i had to sleep with my dad for 5 years and i would have nightmare that she would be right out my window and i thought if I would get up at night she would grab my feet under the bed;" [following a sequence of creepy-puppet videos] "too horrifying for me to even try and find a film of")
And then there is THIS Lady Elaine tribute blog, which . . . words literally fail me. I cannot describe it. I suspect either genuine severe mental illness or a really brilliant imitation of severe mental illness.
³ Really dislike the Burger King mascot. In fact, I have deliberately chosen not to go to Burger King once or twice for a soda, when it would actually have been more convenient to go there, on account of their mascot. I've done that for Quiznos, too, because I am still annoyed by their "Spongmonkey" campaign from 2004. That's right: I have boycotted a sandwich shop for five years because I disliked their commercials. I won't be going to Burger King until 2034 or so.
⁴ Other monsters are maybe more straightforward representations of things that are dangerous, and don't relate to corpses, but those usually involve animals which are dangerous in themselves: werewolves are scary because (among other things) wolves are scary. Vampires are scary because . . . well, actually for vampires you could argue that corpses are involved there as well: they're as much animated corpses as mummies or zombies are. But there's also the whole rabid-bat angle.
⁵ In fact, it's not even difficult for people to develop emotional attachments to things that don't resemble people in the slightest and aren't even alive: people easily project human qualities onto their Roombas, for example. Gamers have reported feeling horrible at having to incinerate the Weighted Companion Cube in the video game Portal -- this despite the WCC does not talk, move, or serve any useful purpose whatsoever in the game and has no human or facelike features.
⁶ Plants for the disabled, who know they wouldn't be able to care for one but want something green in the vicinity; plants for locations where a pot wouldn't be able to fit, or where conditions wouldn't support a live plant; plants for people who spend a lot of time traveling and are unable to give consistent care to a live plant, etc.
⁷ Because people should be free to have plastic plants in their homes if they want to, so long as it's not hurting anybody else. While I find the whole phenomenon icky and strange, I do have to admit that, bottom line, I'm not being hurt by other people having artificial plants. One could maybe argue from an environmental standpoint that plastic plants are objectively bad and harmful to others, but I couldn't make that objection without being a huge hypocrite, so I don't make it.
⁸ Although I am on record as skeptical about the ability of live plants to improve one's air quality in a meaningful way, and don't like seeing this hyped in the way it has been in the last however many years, it's undeniable that live plants will take volatile organic compounds out of the air. This may not happen quickly or improve your life in any meaningful way, but a reduction in formaldehyde is still a reduction in formaldehyde. A plastic plant, on the other hand, is going to add chemicals to the air, if anything. This also probably wouldn't happen quickly or affect your health at all, but even so. Everything else being equal, most of us would rather have less phthalate in the air than more.
If you have some burning desire to avoid real plants, but still want the air-cleaning benefits, get a fake and plant it in soil. You'll probably wind up with a net benefit in air quality, as about 1/3 of the volatile organics taken up by plants aren't taken up by the plants at all: they're removed by the microorganisms living in the soil. Planting an artificial plant in real soil comes dangerously close to dating a blow-up doll, of course, and you risk being committed to an institution by your family, but if you're going to insist on getting some of the benefits of a real plant without actually buying a real plant, here is an option.