Romain, as the 2 bulbs you bought would be offsets from the same bulb, they won't set seed. It needs an unrelated clone to be successful in pollination. And that it not the whole story either. Best to enjoy these as they are. Anders,I suspect that one cannot totally replicate the climate where these ones come from. So it may not be the mix that is the problem. I wonder who else is growing these in cooler/cold climates. As for mix, I use 1/2 pumice, the rest a mix of soil and coarse sand. It is more important to get the watering right. Mine thrive, and are on the porch, get filtered sun I guess. When in growth they need lots of feeding. Once they start to show a leaf which is going dormant, I don't water, although the mix retains quite a bit of moisture, so they are never bone dry. Winter temperatures range from minus 4 - 18ºC. The minus 4 melts off as soon as the sun comes up, and of course the bulbs are protected from that, the porch never gets any frost. Others may have other mixes which work well. This is just my personal experience. https://get.google.com/albumarchive/… Ina On 27/10/2016 9:53 a.m., Anders Bo Petersen wrote: > Romain, I was about to lose mine as well because of the same reasons as you mentioned. I still have the first bulb I bought but it's been growing smaller instead of bigger. I have got some of the cactus mix from the Botanical Garden which consists of 8 different minerals/soil. I know that the it is perfect for many bulb species because they thrive. Would like to hear from other growers what kind of soil mix they use. How often they fertilise and with what. Anders - Copenhagen