I used a 3 gal nusery can...(in my NYC yard). 5 gal would have been better. I did not use a soil mix. I dug up enough soil from my LI property to fill the can, then sank it into the ground- permanently. The acaule's eventually died, not because of the soil, but because my location got overgrown by other plants (azaleas, Japanese maple, and Aesculus) and became too shady for them. C. acaule must have some sun to bloom- best situation is with open trees overhead, so that it gets continual patches of sun during the day, alternating with shade. Direct sun is OK in early spring before trees leaf out. Take care, Eric