Nepenthes eymae is a climbing plant growing to a height of up to 8 m. The two lobes of the peristome are typically separated by a gap of several millimetres under the lid. The peristome ribs are well developed, being up to 2 mm high. The pitcher lid or
operculum is ovate to triangular, growing to 5 cm in length by 3 cm in width. They may be shortly contracted directly below the orifice. Upper pitchers are significantly smaller than their terrestrial counterparts, reaching only 15 cm in height by 8 cm in width. Characteristically, the hollow pitcher tube continues past the curved basal portion of the trap and for a few centimetres up the tendril. This is also commonly seen in
N. flava,
N. fusca,
N. jamban,
N. ovata, and
N. vogelii. The wings are often reduced to ridges, although no vestige of the wings may be apparent in some specimens. These ridges typically run parallel in the lower part of the pitcher, becoming divergent above. The pitcher mouth is horizontal and straight. The peristome is flattened, glossy and up to 1.5 cm wide, being of approximately equal width across its span or broader towards the rear. The peristome ribs are highly reduced but conspicuous, being only up to 0.5 mm high and spaced up to 0.5 mm apart. The rear of the pitcher is elongated into an
acuminate neck (≤3 cm long) that may be vertical or inclined forwards at a considerable angle relative to the pitcher orifice. The peristome's inner margin lacks teeth, while the outer margin is often
sinuate at the base of the neck. The lid is typically
hastate and very narrow, measuring up to 8 cm in length, with basal and middle widths of up to 2.5 and 1 cm, respectively. It bears rounded basal lobes and an obtuse to abruptly rounded apex. It is often curled upwards and may be crenellated at the margins. The presence of appendages is variable in upper pitchers: the lid may possess a pair of appendages as in terrestrial pitchers or may lack them completely. Where these appendages are present, the basal one is hook-shaped and up to 8 mm long and the apical one filiform and up to 12 mm long. The glands of the lower lid surface are similar to those found in lower pitchers. The spur is inserted 10 mm below the lid. It may be simple or
bifid at its apex, and measures up to 10 mm in length. Developing pitchers have laterally appressed walls and a pronounced bulge at the rear, which holds the spur upright. The spur has a closed bifurcation at this point.
Nepenthes eymae has a
racemose inflorescence. The male inflorescence measures up to 30 cm in length by 2.5 cm in width (flowers included), of which the
peduncle (≤3 mm wide at its base) constitutes up to 11 cm and the
rachis up to 20 cm. Flowers are borne singly or in pairs, the two-flowered partial peduncles being located towards the base of the inflorescence. The partial peduncles are
ebracteate and number 30–40. They are approximately 4 mm long, being formed from a pair of basally-united
pedicels around 10 mm long.
Tepals are elliptic and around 4 mm long by 2 mm wide. The
androphore is around 4 mm long and bears an
anther head measuring 1 mm by 1.5 mm. An
indumentum of soft, orange to reddish-brown hairs is often present on all mature vegetative parts, including the stem, lower lid surface, and laminar surfaces. This covering consists of tufted hairs up to 0.05 mm long and simple hairs typically up to 0.8 mm long (those of the tendril, midrib, lid and spur are denser and longer, reaching 2 mm). However, the indumentum is variable and may be reduced to the point of being completely inconspicuous in some populations. The stem and midribs are yellowish green, and the laminae dark green. The tendrils may be yellow to green or tinged red. In terrestrial traps, the pitcher cups may be white, green, yellow, brown, or red, and are often red speckled. Traps bearing a conspicuous indumentum may have a maroon sheen under certain light conditions. The inner surface ranges from yellow or olive green to almost brown, and commonly has darker blotches of red, brown, or purple. The peristome is usually dark, from reddish brown to black throughout in older specimens. It frequently bears stripes ranging from yellow to black. The operculum is green to brown and often mottled with red to black markings on its lower surface. Upper pitcher are predominantly yellow, sometimes bearing red to purple flecks on the inner surface and lid underside. The appearance of the peristome is variable: it may be a solid orange to red (in which case it is often darker towards the inner edge), or it may be narrowly streaked with red, brown, purple, or black.
Tepals are red. No
infraspecific taxa of
N. eymae have been described. ==Ecology==