Nepenthes benstonei /nɪˈpɛnθiːz bɛnˈstoʊniaɪ/ is a tropical pitcher plant endemic to Peninsular Malaysia, where it grows at elevations of 150–1350 m above sea level.

[1] In their 1997 monograph, "A skeletal revision of Nepenthes (Nepenthaceae)", Matthew Jebb and Martin Cheek tentatively referred specimens collected from Bukit Bakar, near Macang, Kelantan, to N. sanguinea.

They noted that the plants exhibited some unusual morphological features, such as larger leaves and decurrent, almost petiolate leaf bases, suggesting that they might represent an as-yet undescribed taxon.

[3][12] Although only described towards the very end of the twentieth century, N. benstonei was probably first collected in July 1911 by Henry Nicholas Ridley on Mount Tahan in Pahang.

[3] For his seminal monograph of 1928, "The Nepenthaceae of the Netherlands Indies", B. H. Danser examined the sheet of Ridley 16097 held in Singapore, lumping it with the variable N. alata from the Philippines.

[2] Danser briefly mentioned this specimen in his discussion of N. alata:[2] The specimen recorded by me from the Malay Peninsula deviates more [from N. alata], especially by the long, narrow inflorescence and 2-flowered pedicels, but also in the Philippines and Sumatra forms with 2-flowered pedicels have been found (Ramos 14650, Lörzing 11603).Danser also treated N. eustachya from Sumatra in synonymy with N. alata, giving rise to a taxon with a puzzling geographical distribution: widespread across Sumatra and the Philippines, apparently very rare in the Malay Peninsula (Ridley 16097 being the sole record), and completely unknown from Borneo and the other major islands of the Malay Archipelago.

Kiew explained the apparent near-absence of N. alata from Peninsular Malaysia as follows:[6] Why has this species not been recollected since 1911 in spite of several botanical expeditions to G. Tahan since then?

Although N. alata Blanco is superficially similar to N. gracillima in its narrow leaf blade which has an attenuate base, the pitchers of these two species are distinct.

[8] They also restored N. eustachya as a separate species, making N. alata a Philippine endemic once again — a circumscription that has been accepted by subsequent authors.

[12][13] However, in his 2001 book, Nepenthes of Sumatra and Peninsular Malaysia, Charles Clarke disagreed with Kiew's identification of Ridley 16097 as N. gracillima.

Kiew partly attributed the narrower leaf bases of Ridley 16097 to a preservation artefact, but Clarke stated that this explanation could not fully account for the differences.

[3] In addition to the two sheets of Ridley 16097, populations of N. benstonei from Mount Tahan are represented by the specimen Holttum 20643, held at the herbarium of the Singapore Botanic Gardens (SING).

[12][16] Specimens from peninsular Thailand originally assigned to N. benstonei in Cheek and Jebb's 2001 monograph, "Nepenthaceae",[8] have since been identified as belonging to a new species, N. thai.

[12] The stem and leaves of N. benstonei bear a thick, waxy cuticle that often gives a whitish-blue sheen to the lamina and pitchers.

It is known with certainty only from the summits of low hills in Kelantan and northern Terengganu,[12][16] and from Mount Tahan in Taman Negara, Pahang.

[12][16] There, its altitudinal distribution appears to be restricted to 450–600 m.[12] The species is also present on Mount Tahan, which at 2187 m is the highest mountain in Peninsular Malaysia.

Though there were no confirmed reports of N. benstonei from Mount Tahan prior to 2012, the species's presence there is attested by much older herbarium material.

[12] Otherwise, N. benstonei lacks remarkable characteristics and is distinguished from related species on the basis of its stem, leaves, peristome, lid, indumentum, and glands of the digestive zone.

The presence of teeth on the peristome of lower pitchers and of a thick, waxy cuticle on the leaves also serve to distinguish these taxa.

[12] Nepenthes benstonei has also been compared to N. albomarginata, although the presence of a white band below the peristome, which gives the latter its name, makes identification easy.

[12] In 2001, Charles Clarke performed a cladistic analysis of the Nepenthes species of Sumatra and Peninsular Malaysia using 70 morphological characteristics of each taxon.

[13] A single example of N. benstonei × N. mirabilis was discovered by Andrew Hurrell at the foot of Bukit Bakar, where the two species occur sympatrically.