1. I live in zone 8a, changed from 7b last year. I have grown crinums for about l0 years. I have never seen any of them stay green over winter. I give them a top dressing of manure each fall and then mulch them well with pine straw. I do not cut them back. The foliage freezes into a black, stringy goo. I leave it right where it is. I believe it insulates the bulbs, whose necks are above ground. In spring, when I see them trying to emerge, THEN I go out and pull all the debris from the previous year off. It will actually be attached to the beginnings of this years' leaves, but is easy to remove. This winter die back has never caused mine to fail to bloom. (I have about 6 to l0 varieties, I guess.)

2. I have lots of Lycoris radiata bulbs and a new this year planting of squamigera. We have had the coldest winter I have experienced here in the sense that we have had very long terms of very cold weather. But still, our coldest temp this year was 9 and that was only for a couple hours on one day. I have seen zero once in 25 years here. All that being said, lycoris foliage is evergreen here every year I have gardened. I have never seen it so much as freeze burn. Radiata blooms in fall here, with foliage following a couple weeks later. It stands all winter and goes dormant with the daffodils. This is my first year for squamigera. I only got the bulbs a few weeks ago from a friend. The foliage was partially emerged when she gave them to me. It is beautiful and healthy right now.

I cannot speak to zone hardiness. Sorry.

This year (zone 6 here), I lost the radiata foliage in December, which wasn't long after they emerged...due to the incredibly harsh winter we had. I'm sure my radiata won't be blooming for a couple years. This has been not the norm....
I have a crinum x powellii (one of the hardiest), and after several years to get the first bulb to maturity, it flowered at least once a year after that. And yes, the foliage has pretty much no frost tolerance....it's gonna go black and slimy easy/early and die back.

Thanks for the info.

My experience is limited to L. squamigera as far as Amaryllids are concerned.

Do you mulch your Crinum x powellii over winter, dbarron? Has it multiplied well?

Oh, and how deep should you plant them? I've read anything from "keep the neck at/above soil level" to "plant 18 inches deep".

I planted quite deep (knowing I didn't want the bulb to freeze) originally. I believe crinums tend to self-adjust on depth (not sure on that). I mulched pretty heavily the first 2 or 3 years.
I had perhaps 5 bulbs with growing points above ground after 7-10 years....not fast multiplication by any means.