It sounds like it gets to little light. If it gets too much heat in the winter it might grow like this to. /David

I don't grow the spineless one, but I have winter hardy Opuntias growing in a raised (enclosed) bed in front of my house in our rather rich Nebraska soil with just a bit of rock mixed in. They come back after the coldest winters. Mind you, they look like hell by winter's end - nearly black and withered. But once it starts to warm, they puff back up and green up, and by June, they're blooming up a storm... I was a bit skeptical myself when I put mine in the ground, so I kept a rooted pad inside in the winter the first couple of years, in case I lost them and had to start over. But they truely are WINTER hardy! Denise in Omaha

About the frozen pad issue, It all depends on what type of PP you have and how cold cold is.. GT, I have to preface this with I live in Zone 8B, so what I say must be taken with a note of caution. I do not know where you are and how your cactus will do. Many cactus harden off by dehydrating and "LYING DOWN" and playing dead. The ice is giving it some insulation. When spring comes it may just stand up once warm IF it is a hardy cactus like O. polycantha, O macrohiza (sp). I have seen this with Prickly Pear. I saw a huge 5 foot O. gomei lie down and smother the cactus below it and then stand up exposing the now dead prized trailing cactus 3 months later. I forgot. That happens when one has too many plants. . I had trimmed its brother of about 200 lbs. of pads and left it as a control to see what would happen. It took a long time but it stood up. It was on the edge of its hardiness range. My neighbors 4 cows broke loose and ate the 200 lbs. of pads in one afternoon. You have a choice of cutting the pad off know and bringing it inside and see if it is viable or leaving it as is , but check it for rot. The pad will not even think of rooting till warm spring/summer so do not put it in soil. Just let it callous .

This may sound negative - but pls. consider all remarks (they may or may not apply to your situation): No need for humidifier for succulents, it actually is not better. They come from arid areas, and humidity is often causing fungal problems. You suggested drafty windows, now you saying they are "nicely insulated" - I was commenting on what you said originally. Most succulents will overwinter well in much lower temps, as low as 45-48*F or so. You don't have to, but need to adjust other growing conditions accordingly. Typical moisture meters are not very reliable, but maybe you have new one that still works well, or better quality one. I find much more reliable way of checking for moisture using bamboo skewer, chopstick or even pencil. Some ppl water successfully from bottom, if using fast draining mix. Very often, typical C&S soil is full of peat and doesn't dry well enough. If that is the case, watering from bottom is worse because it keeps soil too wet for too long. Ppl using C&S soil usually add lot more sifted perlite to it - easily 50% or even more - and that works better. I find it much better using inorganic potting mix (no soil). 10" pot sound huge to me - but that all depends on size of plant and I have no idea about yours. Clay 10" pot is usually quite deep. Big, deep pots hold lots of soil and if it doesn't drain fast, it could be problem. I am assuming it has drainage hole. I am not sure what is wrong with your plant, but it looks like either drying (how close is it to grow light? Was it put under it suddenly - is there any chance it may have burned?), or having fungal problems. I would definitely improve potting mix and keep it in room with no humidifier to begin with.