N. northiana is a litophyte plant. Just have a look here for some in-situ photos:
http://pitcherplants.proboards.com/i...ay&thread=7302
Like epiphytes also litophytes should be grown in very well draining soil. Also it's a good idea to use for this sort of plants rather small pots. My experience with northiana is quite limited. I just grow it for 8 months and it increased well its size and is pitchering regularly. I've got my northiana in a meshpot in a 50/50 mix of sphagnum and expanded clay and the pot has a 5 cm drainage of pinebark and charcoal and it recieves lots of wind from a ventilator.