Yucca guatemalensis (more widely known by the incorrect name Y. elephantipes) is my very favorite houseplant. This is not to say that there aren't others that I like very very much, but I would be nearly inconsolable if I were to lose mine, particularly since I have a couple variegated versions that I haven't seen anywhere else, ever, which wouldn't be easy to replace. The first one of these, with gray variegation, I've had since 1998 or 1999, a couple plant-obsession cycles back (it's also the only survivor from that cycle, since a Sansevieria trifasciata I'd had since 1998 bit the dust about a year ago).
I've gotten a lot of very nice plants through mistaken identity. When I bought the gray Yucca,1 it was just a bunch of leaves with no visible stem in a 4-inch pot, and I thought it was a Dracaena of some kind. (It does sort of resemble a D. deremensis 'Warneckei,' if you're not looking too closely.) So for a very long time I persisted in thinking it was a Dracaena, even though I knew that Dracaenas didn't, for example, have leaves with serrated edges.
Then I moved in 2001, up to the Iowa City area, and my new apartment was many, many times the size of where I'd been living before, so there was a whole bunch of room for new plants. I went to Target and found a couple more Dracaena-like plants, which had sword-shaped, thick but kinda floppy leaves, that were solid green with about a half-inch of yellow on the sides. No serration on the leaves this time2. I thought, well, Dracaenas are supposed to be pretty easy, so why not? And then eventually, again, it became clear to me that this, too, was a Yucca.
So then I met my husband in 2002, and we moved in together in 2006 (he had a cat, I had cat allergies: for this and other reasons3 there was a transitional period from 2004 to 2006 where we kept separate apartments in the same building4). He had a Yucca of his own but had assumed it to be a Dracaena fragrans, because the Yucca was smallish and looked enough like the Dracaena fragrans massangeana it was with that nobody really ever bothered to think about it too hard. Then at some point, I noticed that the little "corn plant" in this group planting of his had leaves with slightly serrated edges, and after some investigation, we concluded that 1) it was actually a Yucca, and 2) it was rotting to death. The group planting was subsequently divided, my husband gave the Yucca to me, whereupon I cut it into pieces and rooted it, making four even smaller plants out of it.
I do not know what Yuccas are hoping to gain by infiltrating Dracaena territory, but clearly they're planning something or another. Be on the lookout. Question your own Dracaenas.
Should war break out between the Yuccas and Dracaenas, my money is on the Yuccas. Their leaves are usually slightly serrated, which would be advantageous in battle, and also terminate in a fairly sharp point. Many species of Yucca have actual spines at the ends of leaves; Y. guatemalensis doesn't, but the leaves are still sturdy enough that they can hurt you if you walk into them wrong. My grower-guide reference book (useful in all kinds of unimaginable ways: here's the Amazon page for it, if you're interested. There's also a second edition, which I was not aware of when I got mine.) says that the author got a punctured eardrum from a Yucca leaf tip. So they're not to be toyed with, but at least they're not overtly mean, like Agaves are.
The other reason I love Yuccas is, they are incredibly tolerant of all kinds of things. The books will tell you that they need very bright light, ideally full sun, and while it's true that they do well in full sun (and they are very grateful if you can swing leaving them outside for a summer), they will put up with a lot less for a long time. During the transitional-apartment period, mine were all a few feet away from a north window, and their growth was unaffected, as far as I could tell. They also seem to be relatively easy-going as far as watering: I know mine have periodically been wetter or drier than they would have preferred, and they've come through it fine, except for one barely-rooted cane section that rooted, and sprouted, but then rotted out when I planted it with three other canes. Overwatering is a much bigger deal than underwatering; a lot of the risk can be eliminated by using an appropriately-sized pot (something that's not huge compared to the root ball) made of clay. Most of mine are in plastic, though, and apparently they couldn't care less.
I've never had any pest problems with mine, though I know they can still be attacked by scale and mealybugs, so you do want to be careful when you pick one out. I also suspect one of mine of being a highway for a spider mite migration last winter, though I have no proof of this, and in any case the mites seem not to have bothered the plant itself, just the plants around it.
The variegated versions are, according to the abovelinked Tropical Foliage Plants: A Grower's Guide (Lynn P. Griffith, Jr.), often more vigorous growers than the plain green kind. This flies in the face of all common sense, but that actually matches my experience pretty well. The yellow-variegated version of mine in particular seems to outgrow the gray-variegated and plain-green plants.
How do you penetrate a Yucca's ingenious disguise, if you see one in the store? Here are some tips.
1) If the leaf edges are slightly serrated (you won't be able to see this, probably: you have to run a finger along the side of the leaf), it's a Yucca. If not, it could go either way.
2) If the newest leaves have a blue-green cast to them (called "bloom"), like the coating on grapes or Echeverias, it's a Yucca. If not, it could go either way.
3) If the leaves have ridges running lengthwise down the leaves, it's a Dracaena. Smooth leaves could go either way.
4) If the leaves are wider than a couple inches (5 cm), it's a Dracaena. Thinner leaves could go either way.
5) If the leaves fall up, out, and down away from the stem in a smooth curve, it's probably a Dracaena. Yucca leaves tend to be heavy enough and thick enough that they will only curve down when they're too heavy to hold themselves straight anymore, so you wind up with two straight segments separated by a kink.
It's not that they're all that special, exactly, in and of themselves, but I really can't help but praise them: they've hardly ever given me a moment of trouble, and there's almost nothing else I can say that about. (Possibly Haworthia retusa, as well: we'll get to it eventually.)
Photo credits: all me.
2 It eventually developed serrations, which is kinda weird when you think about it.
3 (Reasons which are complicated, none of your business, and surprisingly uninteresting anyway.)
4 He gave Tara, his cat, to his parents. They then promptly moved to Minnesota, where Tara was killed by a wild animal of some kind, likely a fox, that broke into their back yard somehow.