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I really like the Altman "Tricho grandiflorus Torch Cactus". They are cheap, tough, vigorous growers for me (once in the ground, and mine are all outdoors.) They take the 100F plus heat, and our cold. I grab some up every spring from the Altman shipments. As stated above, definitely Forrest Gump "box-of-chocolate" plants. You never know what you'll get until they grow/bloom. However, a few of mine have bloomed even when small 3" single stems, so sometimes I get an early clue. My older clumps always bloom reliably. I have white, pale yellow, bright gold-yellow, peach, and red. The blooms are not nearly as large or interesting as the beautiful named Echinopsis hybrids (like Schick hybrids), but I'm happy to trade that for surviving my zone 8a winters. (Notolover, maybe you could try a few of these in the ground?) The bodies of my Altman trichos vary widely too. Some form clumps of tall stems, and some form wide low clusters. Some have dark green bodies with reddish spines, some have light green bodies with gold spines. I enjoy seeing who they grow up to be. My favorite Altman Tricho grandiflorus blooms pale yellow. It was a single $9.99 stem from Walmart about five years ago. Most winters we get down to mid teens, but last year we were below 10F. In the apocalyptic freeze of 2011, we were below zero for days. We lost 40 foot palm and eucalpytus trees, but every Altman cheapie Tricho I had survived. I stuck styrofoam coffee cups on the stem tips, and threw a bed sheet over that...with a few inches of snow, which no doubt helped. I didn't lose a single stem of these...not a scar. That's when I started buying these like a mad woman. (Don't get between me and a new, unpicked Altman shipment.) In contrast, almost all of my named Echinopsis hybrids died in 2011, even though I covered them too. This is one of only two hybrid survivors (purchased as "Cherry Red" although it looks pink.) Before the freeze, it was over twice this big. It grew back, mainly from the base. If you look closely you can see the sickly narrowing of some stems about halfway down, from the big freeze. It's on the sheltered south side of my house, so that's probably why it survived. My only other 2011 hybrid Echinopsis survivor was Flying Saucer, a gift from a very generous friend in 2010. If they're forecasting teens, I stick styrofoam cups/bowls on the stem tips, and wrap it all with old towels and clothespins. It survived the 2011 below-zero freeze this way. I'm lucky that my neighbors are patient about how stupid my yard looks on cold nights. I have Schick echinopsis hybrids in the ground again, and they each get covered with a plastic bucket if it's heading much below 20F. I add sheets/blankets on top if it's threatening lower teens. Sometimes styro cups on the tips (depending on how crazed I am.) The Schicks have made it through two winters, including down to 9F. They are pretty annoyed by the end of the winter (angry shriveled red bodies) but then they forgive me, cheer up, plump up, turn green, and bloom. Regarding the Altman Trichocereus/Helianthocereus grandiflorus babies....I have read discussions elsewhere that the more current name for these is actually Echinopsis huascha. At least, that's how I label them in my yard, along with the note that I bought them as Altman Tricho grandiflorus. Love em. Good cheap low-stress fun. I plan to always have some of these Altman plants mixed in with my fancier hybrid Echinopsis, just because they are more worry-free, and so ploddingly reliable.

this is there time to be dormant..don't water them at all it is just rotting them. if the base rots off replant the green tip. it is a set back but you will still have a plant. I don't even water mine outside that much in 100+ summer temps.

Waz, Looks to me like a globular South American cactus of which I know little about. It's definitely not columnar, AFAICS, so that rules out Trichocereus (even in its latest incarnation as Echnopsis). I think perhaps a Parodia, owing to the length of its long spines (and the arrangement of the radial ones) and the remains of spent flower pods up top. So, if you're looking for where to look, I'd guess Parodia first, Echinopsis second and something like a Gymnocalycium/Soehrensia third, but all of those could not be your cactus, which is a very nicely mounded round o' green.