[2][5] Although once confused with N. vieillardii[5][6] and previously regarded as conspecific with the closely related N. monticola, it is now recognised as a distinct species.

[7] The specific epithet lamii honours Dutch botanist Herman Johannes Lam, who made one of the earliest known collections of this species.

[5][7][8] Herman Johannes Lam, after whom the species is named, made a number of collections of N. lamii during the Van Overeem Expedition of 1920.

[5][7][8] He collected both male and female floral material on October 17, 1920, on the flanks of Doorman Top (now known as Mount Anggemuk), West Papua, at an elevation of 3250 m[3] (or 3200 m).

[8] In addition to the specimens mentioned above, Danser also listed Docters van Leeuwen 10834 as New Guinean material of what he identified as N. vieillardii.

[a] Danser explained his interpretation of N. vieillardii as follows:[3] N. Vieillardii has only been recorded from New Caledonia and the Isle of Pines up to the present, but the materials collected by the latter expeditions have shown, that at least in the western part of New Guinea it is not rare, in the latter country it varies more than in New Caledonia but it seemed impossible to me to distinguish separate species.

A prominent example of this is Matthew Jebb's 1991 monograph, "An account of Nepenthes in New Guinea",[4] where an illustration of N. lamii (figure 27) is labelled as showing N. vieillardii.

[8] In 1994, A. Wistuba, H. Rischer, B. Baumgartl, and B. Kistler observed wild plants of N. lamii (which they called N. vieillardii) during a trip to Doorman Top in search of the enigmatic N. paniculata.

[8] The next detailed treatments of N. lamii appeared in Cheek and Jebb's updated monograph of 2001, "Nepenthaceae",[8] and Stewart McPherson's 2009 work, Pitcher Plants of the Old World, which included colour habitat photographs of the species.

[5] Nepenthes lamii reaches a maximum height of around 4 m, although plants growing towards the upper altitudinal limit of this species are greatly stunted shrublets.

It has an acute to acuminate apex and an obtuse base that may be decurrent for more than 2 cm down the stem, although it is variable in this respect.

Three to four longitudinal veins are typically present on either side of the midrib, restricted to the distal quarter to third of the lamina, although they may number as many as 5 or as few as 0.

[8] Pinnate veins, which may or may not be distinct, emerge obliquely from the midrib to form an irregular network in the distal half of the lamina.

[5] A very sparse covering of pale brown, woolly-scurfy hairs measuring 0.2–0.4 mm is present on developing parts.

The only mature parts that retain an indumentum are the inflorescence and tendrils, which bear an inconspicuously puberulent covering of simple, black hairs of around 0.3 mm.

Papua has been found at similar altitudes of around 3500 m.[5] The species is highly variable in terms of growth habit and stature.

[5] The size and distribution of natural populations of N. lamii are incompletely known, making it difficult to assess the species's conservation status.

[5] However, the populations found near Tembagapura appear to be secure for the time being due to the tight controls on access and development present in the area.

[5] Stewart McPherson writes that N. lamii "may be anticipated from many of the high peaks of central Papua, and the species may accordingly have a wider distribution than is currently appreciated".

[5] Furthermore, although similar, the traps of N. lamii differ in that they have a round, as opposed to angular, pitcher mouth, and mature specimens never have filaments on the upper surface of the lid.

Nepenthes lamii almost completely lacks an indumentum on mature parts, whereas N. vieillardii bears a sparse to dense covering of white hairs measuring around 1 mm in length.