I read with interest the response to Dr Wilcox question re D.
filiformis.
i too grew many of these plants this year, not from seed however, but
from leaf cuttings (i found this to be very effective; ie a high
strike rate, often with 3 plantlets per inch cutting).
hoever they reached similar heights to those mentioned (if 'height'
is appropriate to such small plants!)
they have died back for the winter, but will i expect recover (as
does the mother plant) to produce mature plants in the second
season of growth.
Do not despair! Perhaps it is our climate/daylength.