Nepenthes rajah is known to hybridise with several other species with which it is sympatric. It seems to flower at any time of year and for this reason it hybridises relatively easily. Charles Clarke also notes that N. rajah, more than any other species, appears to have been successful in having its pollen transported over considerable distances. Consequently, a number of putative N. rajah hybrids exist without the parent plant growing nearby. However, it appears that the limit as to how far pollen can be transported is approximately 10 km. Hybrids between N. rajah and all other Nepenthes species on Mount Kinabalu have been recorded. Due to the slow-growing nature of N. rajah, few hybrids involving it have been artificially produced yet.