Nepenthes rajah is comparable to that experienced in nature, since Borneo lies on the equator. 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. The potting medium should be well-drained and not too compacted. Moss is useful for moisture retention near the roots. The mix should be thoroughly soaked in water prior to potting the plant. It has been noted that "N. rajah" produces a very extensive root system (for a "Nepenthes") and,
Sphagnum short-lived, and consists almost entirely of a shiny green, spherical spore capsule that becomes black with spores. Sporophytes are raised on stalks to facilitate spore dispersal, but unlike other mosses, "Sphagnum" stalks are produced by the maternal gametophyte. Tetrahedral haploid spores are produced in the sporophyte by meiosis, which are then dispersed when the capsule explosively discharges its cap, called an operculum, and shoots the spores some distance. The spores germinate to produce minute protonemae, which start as filaments, can become thalloid, and can produce a few rhizoids. Soon afterwards, the protonema develops buds and these differentiate into its characteristic,