Thanks everybody, much appreciated! I think you are right about the first one being S. thurberi. The thought had occurred to me before, but the way it was branching didn't quite seem to match. However, I realize now that it's probably branching naturally only at the base, and that the branches further up were probably all caused by people taking cuttings. I think I read somewhere that thurberis rarely branch in cultivation, but I guess this one doesn't know. Jen, thanks for the Goldfish plant ID - after looking it up I'm pretty sure you're right on that one. Dan: yeah, in that picture I think the Trichocereus(?) is in a 2" or maybe 2.5" pot. shrubs_n_bulbs: I already repotted it shortly after that picture was taken, so it's got some more room to grow now. For comparison, here is a new picture of it together with a larger Pachanoi (which, as you said, is a very quick grower): I'm still not 100% convinced that the small one is a pachanoi - I'm surprised that it's branching that much already, and that the spines are spaced so much closer to each other compared to the larger one in the picture. But, I don't know what young pachanois look like, so it's certainly possible. Thanks for the info on the Agave, it probably is a filifera or toumeyana. Denise, I may take you up on that offer. Maybe I'll have some time this weekend to separate the pups, or maybe I'll do it some time later and send you an email at that point. I have a batesiana hybrid myself too, but that one looks quite different from this and was much more modest when it flowered recently, with a single stalk (though it looks like there is another one on its way). Again, thanks! Fredrik

Keep them warm, in sun most of the time and mist once a week or so. If they're going to root, they should be rooted by spring.

If you have no mold than there's no need to uncover yet. By about 2-3 month mark is when I uncover. It honestly just depends on what's going on in the container. My Ferocactus are uncovered now. Along with a couple other containers that had mold growing. As soon as I uncover the mold stops. I just have to remember to keep moist everyday. Instead of having them covered and not having to worry about them as much. I still have three covered. I will uncover those last three in a month or so. I don't like to keep them covered longer than three months because I feel like they start to need air circulation. Everybody does it different I'm sure. Whatever works:). As long as you keep them moist with some filtered light, they should be fine. All my seedlings are in a north west frosted bathroom window. This would never be enough light for most mature cactus, but the seedlings don't need direct sun. You can see the window in the above pic. That's how much light they get till about 3:30-4:00pm then as the sun is going down they get some sun. I don't know if you've seen this YouTube video, but this guy is germinating Astro seeds. I get the vibe he doesn't keep them covered long at all, but you can see he keeps them very moist because once you uncover the water evaporates pretty quickly:). Video:)

Oof, not an easy question. I'll give it a shot. "Bluish" plants aren't really blue, they'd still feast on the 400 to 700 nanometer wavelength, except they have more of the non-chrolophyll, light-absorbing pigments than do green plants. These accessory pigments harvest green light so plants that have more of them will look less green. It does not necessarily mean they will only use shorter wavelength radiation (blue end of the spectrum), just that they will use more than green plants. Also, even green plants still use some green light because they also have these accessory pigments. I think your purple LED grow light will work fine. I'd just keep an eye on it and watch for stress signs. Alternatively, you can use that bulb on something else and get the full-spectrum LED for your Pilo instead, something in the 7000 K to 10kK range. As long as you're curious (I've slid down that rabbit hole too), look up photosynthetically active radiation. Fun stuff!