Despite being mostly urbanised, Singapore is home to three species of Nepenthes and one hybrid. Nepenthes gracilis, N. ampullaria, N. rafflesiana and N. x hookeriana (ampullaria x rafflesiana) are excellent colonisers of secondary forest and can be found in well drained sections of rainforest throughout the island.
Nepenthes gracilis is the most common species and is characterised by small slender pitchers. In favourable conditions, the basal rosettes can form a dense gathering of larger pitchers. It can typically be found in drier open forest, especially on hillsides.
Nepenthes ampullaria tends to grow amongst the leaf litter and can be hard to spot since the basal leaves are much reduced and the pitchers are often half buried. When mature, this species sends up towering vines that reach high into the canopy – amongst the longest of the genus. The species usually does not grow upper pitchers and instead forms rosettes at regular intervals along their vines.
Nepenthes rafflesiana is the most showy of the three species, growing large pitchers with a mottled red and green pattern. The upper pitchers are particularly elegant and often display an attractively striped peristome.
Where N. ampullaria and N. rafflesiana grows together, the natural hybrid N. x hookeriana is sometimes formed. These plants can be identified by their large leaved basal rosettes, a feature conferred by its N. rafflesiana heritage and squat basal pitchers (alike those of N. ampullaria, albeit with a larger lid).