Interesting collection of information is provided in the link above. I tried a couple times to grow it; unsuccessfully. However it did 'volunteer' at the base of a Asiatic Crinum. It is noted that aparently amaryllid roots support a microbe that psilotum may require. Mine is growing in the ground in zone 9a with winter temps occasionally reaching 32F, though ground temps likely remain closer to 40. However, it has been in the mid 30s for the past three days. We'll see if it survives.