Nepenthes flava /nɪˈpɛnθiːz ˈflɑːvə/ is a tropical pitcher plant endemic to northern Sumatra, where it grows in montane forest at 1800–2200 m above sea level.

[1][2] The specific epithet flava is derived from the Latin word for "yellow" and refers to the typical colouration of the plant's upper pitchers and other vegetative parts.

[2] Whereas the type description mentions a basal crest on the underside of the lid,[1] McPherson writes that no appendages are present in either lower or upper pitchers.

[2] Nepenthes flava is a climbing plant growing to a height of 6 m.[2] It only remains in the rosette stage for a short time before transitioning into a scrambling vine.

The stem, which may be branched,[2] is around 3 mm in diameter and has roughly cylindrical internodes measuring up to 14 cm in length.

[2] On the inner margin of the peristome, these ribs terminate in teeth up to 1.5 mm long, with the largest located towards the rear.

[2] The peristome is usually darker than the rest of the pitcher, typically being dark orange to purple,[2] although it may be creamy white and occasionally exhibits red stripes.

The lid has a similar colour to the pitcher cup, usually having a darker upper surface with dark red speckles.

[2] Characteristically, the hollow pitcher tube often continues past the curved basal portion and for some distance up the tendril.

Young parts of the stem bear a sparse covering of reddish-brown, basally branched hairs (0.2–0.5 mm long).

A dense indumentum of reddish-brown hairs (0.5–1 mm long) is present on developing pitchers and tendril ends.

[1][5] The typical habitat of N. flava is upper montane mossy forest[2] dominated by Rhododendron and Leptospermum plants.

[1] It often grows terrestrially in more open areas of forest, where the vegetation rarely exceeds 4–5 m in height.

Indeed, this trapping method is employed by the closely related N. inermis, which also produces highly viscous pitcher fluid.

[1][2] Nepenthes flava differs from this species in that its upper pitchers are markedly smaller and have a peristome that is significantly narrower, bears distinct ribs, and has an undulate margin.

[2] With N. inermis, this species shares similarly infundibular pitchers, a narrow lid, and the habit of rapidly transitioning from a rosette to a climbing plant (with associated sudden internode elongation).

[1] The describing authors considered N. flava to likely represent an evolutionary link between the pair of N. inermis and N. jacquelineae and "common Sumatran species such as N. ovata".

[2] Nepenthes flava can be distinguished from all of these species on the basis of a combination of features: entirely yellow upper pitchers; a broad, wavy peristome; very small peristome teeth; and a narrowly ovate or elliptic lid that lacks appendages[2] (or has a small basal crest).

[2] Two natural hybrids involving N. flava have been recorded; the describing authors found examples of crosses with N. ovata and N. rhombicaulis.