WCW said she'd tried Medinilla cvv. (rose grape, medinilla) indoors before, and it hadn't done that well for her, but I don't remember any details beyond that. I also know that they tend not to do that great in the ex-job's greenhouse in the long term,1 though that hasn't stopped them from ordering them more than once.
When I googled Medinilla, I found a lot of photos of them indoors in containers, usually in pristinely clean and expensive-looking surroundings, accompanied by breathless, over-caffeinated ad copy about what wonderful, wonderful houseplants they are. So it's possible that we'll be seeing a lot more of them in the future. I'm not sure how I feel about this.
I can't say I've ever had any strong urge to try growing Nandina domestica (heavenly bamboo, sacred bamboo), so I haven't been terribly bothered by not being able to find one. It's my understanding that they're not particularly beloved outdoor plants, though most of the objections raised at davesgarden.com have to do with their rapid spread and drought tolerance, both of which would be a positive indoors. ("Tacky-looking / cliched," "I think I'm allergic," "ecologically disastrous," and "poisonous" are also represented.)
Although Nandina is an FLEPPC Class I (has produced documented ecological damage) invasive plant, it's not illegal to produce it or sell it in Florida. Since there's no legal barrier, I expect that they're unavailable in the north due to a lack of demand.
Neomarica spp. (walking iris, apostle plant) are apparently mostly passalong plants, so there's no money in producing them commercially. I don't know what they're like to grow indoors, and I haven't personally seen anybody growing one, but by most accounts they're pretty easy. (I'm somewhat interested in getting a Neomarica, eventually, someday.)
When my Osmanthus fragrans (sweet olive, tea olive) first arrived, I had it in the house, hoping for ongoing blooming so we'd get to smell the flowers all the time,2 but it didn't bloom. And then it got spider mites. So it spent the summer outside. It seemed to like that well enough, though it didn't grow very much, and it didn't rebloom out there either.
Then, after it came inside, it dropped a lot of the new leaves it had just grown. So we don't seem to be getting along, is kind of the upshot. Some googling brought up this page from the Missouri Botanical Garden, in which it is said "In St. Louis, grow in containers which must be overwintered indoors in bright cool locations."
Which probably explains it, 'cause mine's in a warm dim location. So I'll try to fix that and then get back to you.
None of this explains why I never see them for sale. (I'd think they would sell really well, given the fragrance.) This Garden Web thread suggests that Osmanthus might be another plant that would rather have an unheated sunporch than central heating.
I feel like I pretty well covered the reasons why Pandanus spp. (screw pines) might not be more available in their profile, but in case you don't want to read it all: both Pandanus utilis and P. veitchii can get huge; both have sharp, unpleasant spines along the leaf margins and on the underside of the leaves along the midrib; P. veitchii is so easily propagated that it's probably a passalong. These all seem like perfectly good reasons why they might not be found in retail very often.3
I'm still trying to get a P. utilis of my own, though. Someday.
I've seen Phoenix roebelinii (pygmy date palm, miniature date palm) at the ex-job once, I think, when I first started working there, and I've run into them at Lowe's occasionally since then, but they're not easy to find around here. Something that isn't always obvious from their photos in the books is, they're full of extremely sharp, long (to at least 3.5 inches / 9 cm!) thorns, especially near the base of the fronds. Worse, when I started working there, the ex-job's Phoenix was displayed underneath a huge Ficus benjamina, which dropped leaves into it all the time. Much blood was shed before I learned that there was just no safe way to get the Ficus leaves out of the Phoenix pot, and decided to move the Phoenix instead.
The thorns are bad enough that I'd never actually want to own one myself, but even if I did, Phoenix also gets too large for me, "pygmy" date palm notwithstanding. It probably also needs more sun than I have. Those might also be factors for other people.
Nobody seems to grow Pilea microphylla (artillery plant) on purpose anymore, and I've only seen it deliberately sold once (and that was a strangely-colored variety). On the other hand, I still run into it in stores on a pretty regular basis: they're weedy, and hitchhike in the pots of more desirable plants.
I've grown it once; I pulled it out of some other plant's pot and gave it its own. That worked fine for several months, and then it suddenly collapsed. I have no idea why. (The timing and location were such that scale might have been a factor. I don't know.) I wasn't that crazy about it in the first place, so I haven't tried to replace it.
I don't find Pittosporum spp. (pittosporum, Japanese mock-orange) very interesting. Apparently the flowers smell nice, but the look of the plants, even the variegated ones, do nothing for me. But hey, some people juggle geese.
I gather Pittosporum also prefers cool temperatures during the winter, and is therefore probably another victim of changing home construction, though I'm not 100% sure on that. According to Monrovia, they're only cold-hardy to USDA zone 8, so you wouldn't think they'd want a lot of cold in the winter. I don't know.
Portea spp. (no common name)4 aren't particularly common in the houseplant books, granted, but the Powell book lists a whole bunch of bromeliads I've never seen for sale, and this is one of them, so Portea is kind of standing in for all those (which also include Bromelia, Catopsis, Nidularium, and Quesnelia). The photo above was the best one I found for showing the leaves and inflorescence at the same time, but doesn't do a particularly good job selling the plant overall: it might be clearer why Portea would be desirable from some of the photos of inflorescences. (P. alatisepala, P. kermesina, P. leptantha, P. petropolitana. Don't skip that last one; the colors are particularly interesting.)
The leaf margins are heavily spined, which might explain some of the problem with Porteas (though it doesn't look any worse than some of the Aechmeas or Neoregelias I've seen for sale). Beyond that, there's no obvious problem. Poking around with Google turned up some evidence that they may need a lot of sun, and some of them do get large. They are sold here and there on-line as outdoor plants for people in tropical climates, so it stands to reason that they could be put on trucks and shipped north as easily as anything else could. I'd be interested in a Portea someday, too.
I've personally met a couple people who grew Punica granatum (pomegranate) indoors, and the ex-job was selling them the last time I was there, so Punica isn't missing from retail as much as just exceedingly rare. (That's the only time I can recall seeing them in retail.) Not sure why that is; by one of those people's accounts, it wasn't particularly difficult, though I don't know how long he'd had it.
The Missouri Botanical Garden suggests that the species is probably not that easy to keep indoors, but the variety P. granatum 'Nana' is better suited to use as a houseplant. The comments at davesgarden.com were all uniformly positive on 'Nana' as well, though it's not clear where they were all buying their plants.
I'm desperate to get a Pandanus utilis someday, even knowing that I don't have room for it. I could sort of understand why someone might want to own any of the others, too, but I'm only really interested in Pandanus, Neomarica, and Portea.
- Miltoniopsis spp./cvv. (pansy orchid): have seen very occasionally, in orchid-specialist contexts.
- Myrtus communis (myrtle, true myrtle): have never seen.
- Nerine bowdenii (spider lily): have never seen. (Wikipedia suggests some of the reason could be because they respond badly to being moved.)
- Nicotiana (flowering tobacco): some cultivars seasonally available as annuals or as seeds, but I've never known anybody who was growing them year-round indoors.
- Nidularium (bromeliad): never seen.
- Olea europaea (olive): rarely seen, and super-expensive when they are seen.
- Pentas (pentas, star flower): seasonally available as annuals.
- Petrea volubilis (queen's wreath, sandpaper vine): never seen. (Images from Google show a huge, vining plant that I imagine doesn't stay contained for very long.)
- Philodendron hastatum (silver philodendron): have seen occasionally at the ex-job.
- Pleione formosana (Himalayan crocus, windowsill orchid): have never seen, though it's possible I've seen hybrids for sale at some point.
- Plumbago spp. (plumbago, leadwort): as outdoor perennials; never as houseplant.
- Primula (primrose, auricula, cowslip, oxlip): seasonally as temporary indoor plants.
- Quesnelia (bromeliad): never seen.
As with the other posts in this series, readers are encouraged to leave comments about their experiences with seeing, buying, or growing any of the above, or speculating on why I don't see them for sale (especially if your speculation conflicts with mine).
2 (previous Osmanthus post here)
3 There's also the matter of customers not buying them even when given the opportunity. Oh how I tried, but customers are not that into four-foot-wide (1.2 m) plants where every leaf has three rows of hooked spines pointing in different directions, no matter how easy you tell them the plant is to grow.
4 And no, this is not a misspelling of the better-known plant Protea.