I don't think there are actually any plants that are genuinely black black, but quite a few of them can come close, usually as very dark greens, reds, or purples.
There are also a couple very dark grays out there, but they're few and far.
As a group, these don't photograph terribly well. Too much light and they no longer look black; too little light and you can't see them against a dark background.
As always, I am aware that I've left things out, because there's no way not to. So I'm open to suggestions if anybody wants to leave some.
Alworthia 'Black Gem.' I know it doesn't look like it in this photo. That's because it's not. Grown in bright light, though, this will turn a very dark green-black.
Begonia rex-cultorum 'Harmony's Red Robin,' and other Begonia cvv. to greater or lesser degrees. This is not a good example, since the leaves are mostly red, but the solid-color, darker plant I have, which is 'Texas Coffee Star,' 'Gladys Meyer,' 'Black Coffee,' or something like that, photographs weirdly.
Calathea NOID, possibly 'Medallion.' Also some other Calathea cvv. Usually just very dark green, though the leaves usually have a red or purple back to them which makes them look a little darker.
Ficus elastica 'Burgundy.' (rubber plant) The exact color depends on how the light hits it and growing conditions, but this is also a very good approximation of black.
Ludisia discolor. (jewel orchid; Ludisia discolor) Very dark red.
Ophiopogon planiscapus 'Niger.' (black mondo grass) Very dark green. Not much of a houseplant, really: it doesn't do a lot indoors. But it can be grown there. And it's very, very dark. So.
Pellionia pulchra. (watermelon plant) Very dark gray with even darker veins. This picture makes it look greener than it appears under normal circumstances.
Schefflera (Dizygotheca) elegantissima (false aralia) I still prefer calling it Dizygotheca, partly because it seems more appropriate for a plant with such dark green leaves to have a name containing the word "goth."
Zingiber malaysianum. (midnight ginger) Very dark red, sometimes verging on dark orange. Older leaves may be more green than red, especially in lower light.
If I had to choose just three, Alworthia 'Black Gem' would definitely make the cut, as would Zingiber malaysianum and probably Schefflera elegantissima. Though there are others in the above list I like, too. Alworthia 'Black Gem' is definitely the easiest of the above, and it self-propagates well, which are both endearing qualities as far as I'm concerned. Zingiber malaysianum is much harder (somewhere around a 6.1 on the difficulty scale), but the color of the leaves is fun (especially when light is shining from behind them), and the plant also has a light, spicy, gingery scent, which is only appropriate since it's a ginger.
Schefflera elegantissima, which I am still calling Dizygotheca in my head, is also kind of a pain, mostly with regard to pests, but the color and shape are either unique or very uncommon, and at least one of my plants is growing very well for me. (I had three others at one point in the past, which did not.)
- Aechmea 'Black Chantinii'
- Aeonium 'Zwartkop'
- Alocasia 'Frydek?'
- Aloe variegata (in bright light)
- Anoectochilus chapaensis (jewel orchid) (strongly resembles Ludisia discolor)
- Anoectochilus formosanus (Taiwan jewel orchid)
- Anthurium x 'Marie'
- Aphelandra squarrosa (zebra plant)
- Codiaeum variegatum, some cvv. (croton)
- Colocasia cvv., some cvv. (elephant ear)
- Cordyline fruticosa, some cvv. (ti plant)
- Cryptanthus cvv. (some cvv. like 'Black Mystic')
- Cyclopogon elatus (jewel orchid) (strongly resembles Tradescantia zebrina in the davesgarden photo)
- Dossinodes Indra's Net (jewel orchid)
- some Episcia varieties (flame violet) have dark gray or brown leaves
- Ficus benjamina 'Midnight' ('Midnight' ficus tree)
- Ficus microcarpa (at least some cvv.; the one I have cuttings of is very very dark, except for new growth)
- Goodyera reticulata (jewel orchid)
- Haworthia attenuata (zebra plant)
- Haworthia limiifolia var. limiifolia (fairy washboard)
- Haworthia pumila
- Macodes petola (jewel orchid)
- Maranta leuconeura 'Marisela,' other M. l. cvv. to some degree or another (prayer plant)
- Nematanthus cvv., some cvv. (guppy plant)
- Neoregelia cvv., some cvv.
- Peperomia caperata, some cvv. (Emerald Ripple, ripple peperomia)
- Philodendron 'Black Cardinal'
- Philodendron 'Imperial Red'
- Philodendron 'Pink Princess'
- Pilea involucrata 'Norfolk'
- Pilea 'Silver Tree'
- Sansevieria trifasciata, some cvv. (snake plant, mother-in-law's tongue)
- Solenostemon scutellarioides, some cvv. (coleus)
- Syngonium wendlandii?
- Tradescantia zebrina (wandering Jew)
- Vriesea ospinae var. gruberi
- Vriesea splendens (flaming sword)