Looks like your basic Yucca flaccida, a widepread and remarkably hardy form. Can be grown in areas as cold as zone 4. Not really a cactus - it is a member of the asparagus family.

And no, it won't die once the flower is done :-)

Thank you! That makes sense. I read up on it a bit. The fact that the outer leaves are droopy suggests that this is indeed Flaccida. I read that the flowers usually emerge in "late spring", though, which isn't what is going on here. In fact, there are evidently a few of these in the neighborhood blooming right now. My others are not blooming, but they are all smaller.

Sure it's not Yucca recurvifolia? Or also Yucca gloriosa. Some combine them in one species, others split them, and there can be hybrids.

In either case, they can bloom in Fall and can grow with large trunks. .

I think flaccida blooms in summer and I don't think it forms a trunk (similar to filamentosa, glauca)

This post was edited by dave_in_nova on Wed, Oct 15, 14 at 8:17

The leaves of mine recurve, which I gather Gloriosa does not. But Recurvifolia? Hmmm.

Let me ask this. When the flower is done, can I slice off the big flower stem and plant it? Is that a way to propagate? In the past, I've just hacked off the main trunk and replanted the top. The stump that remains resprouts by itself. But planting the used flower stem keeps the original plant looking good.

This post was edited by daninthedirt on Wed, Oct 15, 14 at 10:15

This is new to me. Your yucca does not die after blooming.
All of my yucca filamentosa died once it bloomed, but new shoots always came up from the bottom of the main trunk.

You can root most trunking yuccas, but not just using the flowering stalk to my knowledge. The flowers and flower stalks eventually dry up.

Gloriosas and recurves have many intermediate forms. Yours looks more like a recurve to me. How tall was it (trunk) when it fell over?

Thanks. I won't waste my time with the flower stalk. I seem to recall that the trunk on the original (which gave rise to my four other plants) was just a foot or two high when it fell over. These aren't big plants. I propagated the other two by just decapitating a trunk before it fell over.