Nepenthes rajah is a montane species or "highlander", growing at altitudes ranging from 1500 to 2650 m.
Pure long-fibre Sphagnum moss is an excellent potting medium, though combinations involving any of the following - peat, perlite, vermiculite, sand, lava rock, pumice, Osmunda fibre, orchid bark and horticultural charcoal - may be used with equal success.