[3]: 123  Nepenthes rajah grows exclusively on serpentine substrates, particularly in areas of seeping ground water where the soil is loose and permanently moist.

Due to its localised distribution, N. rajah is classified as an endangered species by the IUCN and listed on CITES Appendix I.

[2] The species was collected by Hugh Low on Mount Kinabalu in 1858, and described the next year by Joseph Dalton Hooker, who named it after James Brooke, the first White Rajah of Sarawak.

[14] The peristome has a distinctive scalloped edge and is greatly expanded, forming a red lip around the trap's mouth.

[6][3]: 122  The individual flowers of N. rajah are produced on partial peduncles (twin stalks) and so the inflorescence is called a raceme (as opposed to a panicle for multi-flowered bunches).

[3]: 122  Like all Nepenthes species, N. rajah is dioecious, which means that individual plants produce flowers of a single sex.

The first observation dates from 1862 and was made by Spenser St. John, who accompanied Hugh Low on two ascents of Mount Kinabalu.

[11] In 1988, Anthea Phillipps and Anthony Lamb confirmed the plausibility of this record when they managed to observe drowned rats in a large pitcher of N.

[19] N. rajah occasionally traps other small vertebrates, including frogs, lizards and even birds, although these cases probably involve sick animals, or those seeking shelter or water in the pitcher, and certainly do not represent the norm.

[12] Nepenthes rajah has evolved a mutualistic relationship with mountain treeshrews (Tupaia montana) in order to collect their droppings.

[19][26] Whereas the mountain treeshrew visits pitchers during daylight hours, the summit rat is primarily active at night; this may be an example of resource partitioning.

[26] Although Nepenthes are most famous for trapping and digesting animals, their pitchers play host to a large number of other organisms (known as infauna).

The question of whether infaunal animals "steal" food from their hosts, or whether they are involved in a mutually beneficial (symbiotic) association has yet to be investigated experimentally and is the source of considerable debate.

[28] The two species were found to live in association with larvae of Culex (Lophoceraomyia) jenseni, Uranotaenia (Pseudoficalbia) moultoni and an undescribed taxon, Tripteroides (Rachionotomyia) sp.

[33] Spenser St. John wrote an account of his encounter with N. rajah on Mount Kinabalu in his 1862 Life in the Forests of the Far East.

[35] Shortly after being introduced into cultivation in 1881, N. rajah proved very popular among wealthy Victorian horticulturalists and became a much sought-after species.

[36] A year later, young N. rajah plants were displayed at the Royal Horticultural Society's annual show for the first time.

[37] The specimen exhibited at the show by the Veitch Nurseries, the first of this species to be cultivated in Europe, won a first class certificate.

[39] Dwindling interest in Nepenthes at the turn of the century saw the demise of the Veitch Nurseries and consequently the loss of several species and hybrids in cultivation, including N. northiana and N. rajah.

By 1905, the final N. rajah specimens from the Veitch nurseries were gone, as the cultural requirements of the plants proved too difficult to reproduce.

[40][a] N. rajah was featured in the first episode of Kingdom of Plants 3D, a natural history series presented by David Attenborough.

[42] N. rajah grows exclusively on serpentine soils with high concentrations of nickel and chromium, toxic to many plant species.

[43] N. rajah has an altitudinal distribution of 1,500–2,650 m (4,920–8,690 ft) above sea level[8][3] and is thus considered an (ultra) highland or Upper Montane plant.

[44] In the upper limit of its range, night-time temperatures may approach freezing and day-time maxima rarely exceed 25 °C (77 °F).

The relatively open vegetation of the upper montane forest also experiences greater fluctuations in temperature and humidity compared with lower altitudes.

[1] It is listed on Schedule I, Part II of the Wildlife Conservation Enactment (WCE) 1997[45] and CITES Appendix I,[2] which prohibits commercial international trade in plants collected from the wild.

[47] The recent advent of artificial tissue culture, or more specifically in vitro, technology in Europe and the United States has meant that plants can be produced in large numbers and sold at relatively low prices (~US$20–$30 in the case of N. rajah).

In vitro propagation refers to production of whole plants from cell cultures derived from explants (generally seeds).

[48] The plants in the wild are further threatened by climate phenomena including El Niño; the 1997/98 event and subsequent drought had a catastrophic effect on the Nepenthes on Mount Kinabalu.

[3] It is likely that the misconception was popularised by Shigeo Kurata's 1976 book Nepenthes of Mount Kinabalu, in which he states that "N. rajah is rather fond of wet places like swamps or the surroundings of a waterfall".