Nepenthes longifolia (/nɪˈpɛnθiːz ˌlɒŋɡɪˈfoʊliə/) is a tropical pitcher plant endemic to Sumatra, where it grows at elevations of between 300 and 1100 m above sea level.

The specific epithet longifolia, formed from the Latin words longus (long) and folius (leaf), refers to the exceptionally large leaves of this species.

[6] Nepenthes longifolia was formally described[note b] by Joachim Nerz and Andreas Wistuba in a 1994 issue of the Carnivorous Plant Newsletter.

[2] Matthew Jebb and Martin Cheek treated N. longifolia in synonymy with N. sumatrana in their 1997 monograph, "A skeletal revision of Nepenthes (Nepenthaceae)".

[4] The authors tentatively upheld this synonymy in their 2001 revision, "Nepenthaceae", writing:[5] Although we treat N. longifolia as a synonym [of N. sumatrana], it is representative of other specimens from inland Sumatra, at higher altitudes (c. 1000 m) that show differences from the plants at sea level on the coast.

The inland plants have more slender pitchers which are ellipsoid in the lower half and cylindrical in the upper (not infundibuliform), with an elliptic (not a suborbicular) lid.

It grows terrestrially in dense, shady lowland or submontane forest on steep sandstone slopes and ridges.

[2][6][note c] Around the river Tjampo in West Sumatra, N. longifolia is sympatric with N. adnata, N. albomarginata, N. ampullaria, N. eustachya, N. gracilis, and N. reinwardtiana.

[6] On Mount Tjampo itself, N. longifolia grows in a number of isolated patches and is sympatric with N. albomarginata, N. eustachya, and N.

[6] In 2001, Charles Clarke suggested a revised status of Vulnerable for N. longifolia based on the IUCN criteria.

[6] The habitat of this species may be threatened in the near future by fires deliberately started to clear forest for agricultural purposes.

[6] Nepenthes longifolia is thought to be most closely related to N. sumatrana; the stem and lamina of these species are virtually identical in appearance.

Those of N. sumatrana are ovoid throughout, with an orbicular lid and the hip immediately beneath the peristome, and are contracted at an angle of 45° to the mouth.

In addition, the upper pitchers of N. longifolia do not give off a noticeable smell, whereas those of N. sumatrana have a sweet, fruity fragrance.

[6] In their description of N. longifolia, Nerz and Wistuba also used the structure of the inflorescence to distinguish these taxa,[2] but subsequent observations have shown that both species produce one- and two-flowered partial peduncles.

It can be distinguished from that species on the basis of its fringed leaf margins, very long tendrils of rosettes, upper pitchers that are cylindrical above the hip, and the notched peristome which is not greatly expanded near the lid as in N.

[6] Plants that resemble the type of N. longifolia grow along the road from Sibolga to Tarutung in North Sumatra.

[6] Nepenthes beccariana was described by John Muirhead Macfarlane in 1908 based on a specimen collected on Nias, an island located approximately 120 km from the port town of Sibolga.

Twenty years later, B. H. Danser synonymised the taxon with N. mirabilis in his seminal monograph "The Nepenthaceae of the Netherlands Indies", although he did not see the type specimen of N.

[9] In 2000, Jan Schlauer and C. Nepi examined the type specimen of N. beccariana and noted significant differences between it and N. mirabilis, suggesting that it should be restored as a distinct species.

[6] In 2001, Clarke published a cladistic analysis of the Nepenthes species of Sumatra and Peninsular Malaysia based on 70 morphological characteristics of each taxon.

[11] Nepenthes eustachya × N. longifolia has been recorded from a number of locations near Payakumbuh and Sibolga, where its parent species are sympatric.

It is relatively rare because N. eustachya and N. longifolia occur in markedly different habitats; the former usually grows in exposed, sunny sites, while the latter is more common in dense, shady forest.

It can be distinguished from N. longifolia on the basis of its shorter tendrils and the presence of longitudinal furrows on the surface of the lamina, similar to those of N.

[6] Folia mediocria, lamina oblongavel lanceolata, nervis longitudionalibus utrinque 3-4, basi in alas 2 decurrente; Ascidia rosularum mediocria, parte inferiore ventricosa os versus cylindrica, ails 2 fimbriatis; ascidia facie ventrali sub peristomio elevata quomodo peristomio inter alis distinctissime undulato, operculum versus acuminato et elevato, ad 6 mm lato, costis 0,2 mm distantibus, dentibus 0.

Ascidia superioria magna, e parte inferiore anguste infundibuliformi tubulosa, costis 2 prominentibus, ascidia facie ventrali sub peristomio elevata quomodo peristomio inter alis distinctissime undulato, operculum versus acuminato et elevato, ad 6 mm lato, costis 0,2 mm distantibus, dentibus 0.