Hi anthro,
N. Khasiana is the most cold tolerant nep.

- Adrian

how hardy is it? i always thought that N. ventricosa cold hardy to 5'C

My N.ventricosa takes occassional brief temps down to 0oC if protected from frost. The same can be said for tobaica, sanguinea and highland forms of alata and maxima. N.khasiana is equally if not a little more tolerant. Many hybrids using these species (especially with other highlander parents) will also take these temperatures. By brief I mean a few hours max. Don't expect them to be happy if your day temps stay at that temperature.

could they be placed in a warmish shed for the winter?