Your wonderful article fascinated me to the point of planning to hunt down a Piggybacker as my next houseplant. However, thanks to your concluding statements about its toxicity, and in the interest of protecting our beloved house pets, I've decided to pass!
The toxicity is way overestimated. In fact this plant is being used in Russia as a healing plant (of course caution is necessary not to overdose). The small plantlets, when falling down, are not really dangerous! I guess a mid-size dog would have to eat at least 30 of these plantlets to start having problems. I've been giving almost daily very small pieces of Kalanchoe daigremontiana leaves for YEARS to my dog, because she had cancer (and she was too old for a complicated surgery). I'm not sure if it helped, but it didn't do any harm to her for sure. I have read a lot of articles about the healing abilities of this plant, I would never risk any health damage.
BTW: I use "normal" potting soil, withou any drainage, because this plant wants a lot of water during active growth (I even tried hydroponics instead of soil and it thrived!). I really like it, because it's so easy to grow. However it needs a lot of light and it suffers during winter, so I have to cut it in early spring and let it root in water.
Very interesting! I didn't come across any mention of it being used medicinally when I was researching for the article. Could you point me to any resources about that?
I know that if my beagle ate just a few plantlets, it probably wouldn't have done any serious damage. However, I also have a cat that has eaten many houseplants down to nubs, and he also likes to stalk along the window ledge where I had it precariously balanced. My greatest worry was that he'd eat it (he's already gone into kidney failure once due to something he ate when he escaped the house once), or that he'd knock it off the sill, and the dog would eat a significant amount of it. Both pets have had some serious health scares in the past few years, and I certainly don't want to do anything that will contribute to another one!