Dave,
this is a good question! I grow this plant for 10 years and keep it frost free over the winter in my house like Pleiones (0°C - +10°C max.), because I am not sure about the hardiness in my country. The last year I have changed the substrate, now I use a normal garden soil with grit and bims, and now it is flowering very well and is growing much better. When the plant starts to grow I put the pot outdoors (not sunny) where we have 2000 - 2500m rain/year.