This is for any would-be cactus enthusiast that didn't know where to start. I bought this Gymnocalycium (papschii or closely-related hybrid) around 2.5 years ago, and since then it has been one of the most reliably blooming plants that I own. As one might expect from a cactus, it seems to feed off of heat and punishing sunlight, and the hotter and brighter it is, the more it thrives. Given those conditions, it blooms basically constantly between June and August, with one flower coming up nearly immediately after the previous one fades.
Like most cacti, the blooms open at dawn and fall away at dusk on the same day, so it's sometimes difficult to catch them if you aren't paying a lot of attention. The flowers are a spectacular, near-perfect white, and the diameter usually matches that of the entire plant.
You can also see that it is sending little buds off all around itself, so in another couple years I will have that many more little tiny Gymnocalyciums (to give away). Last winter I accidentally let this cactus dry completely out, which it's not a massive fan of, and consequently the dermis on the smaller pups died. I was worried that they would not be viable at all, but you can see that they're starting to grow out again, despite being all-but-dead, which attests to the durability of this particular specimen.
I haven't tried leaving it outside in extreme cold, nor will I, but it's a compact grower so it is no problem bringing it inside for the winter. It also hasn't seemed to ever need any sort of acclimation. As soon as it's warm enough to stick it outside, I stick it outside in the glaring sun, and it goes about its business.
A lot of cacti are sort of fussy about water regulation, which is why I have tended to stick mostly with opuntioids (because they are basically the opposite), but this seems to be more on the thirsty end of the spectrum both during dormancy and moreso during growth. The spines aren't particularly spiny, and on Gymnocalyciums they wrap around the body, so I just give it a little squeeze every now and then and if it isn't rigid, I give it some water. That relationship seems to be fine with both of us.
