[5] The earliest known collection of N. tobaica was made by Johannes Elias Teijsmann on February 8, 1856, probably from the Batak regions.

[6] Nepenthes tobaica was formally described[note a] in 1928 by Dutch botanist B. H. Danser in his seminal monograph "The Nepenthaceae of the Netherlands Indies".

[note b] Danser suggested a possibly conspecific species in N. reinwardtiana:[2] "N. tobaica has only been found on the plateau north, east and south of Lake Toba.

[5] Some plants sold in the horticultural trade under the name N. tobaica are likely to represent a manmade cross between N. khasiana and N. ventricosa.

However, mature plants may have angular stems because of a groove that originates at the node and extends across most of the internode's length.

A pair of wings runs down the pitcher's ventral surface, often bearing fringe elements either throughout the whole length or only in the upper part.

[5] Upper pitchers are typically somewhat infundibular in the lowermost part, becoming narrowly ovoid in the lower third, and finally cylindrical and slightly narrower above.

[5] Around the town of Prapat, plants have been observed to come into flower in April, although mature fruits are not common at this time.

The sepals of this species are densely tomentose, but the rest of the inflorescence has a sparser covering of short hairs.

[5] In some forms, the underside of the lid is a vivid red, making the plants particularly easy to spot amongst other vegetation.

Its natural range was once thought to stretch from the Gayo Lands of Aceh in the north to Tarutung in the south.

These include Mount Sorik Merapi and a unique high altitude peat swamp habitat near Lake Kerinci in Jambi.

[5] Nepenthes tobaica commonly grows in forest edges, where it is often sympatric with species of Leptospermum and Rhodomyrtus.

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

Five natural hybrids involving N. tobaica have been recorded to date; specifically, crosses with N. ampullaria, N. reinwardtiana, N. rhombicaulis, N. spathulata, and N.

[5][13][14] Folia mediocria sessilia, lamina lineari-lanceolata, nervis longitudinalibus utrinque 0-1, raro 2, basi lata semiamplexicauli ; ascidia rosularum ignota ; ascidia inferiora parte inferiore anguste ovata, medio angustata, os versus infundibuliformia, alis 2 fimbriatis, peristomio operculum versus acuto, cylindrico, 1/2-1 mm lato, costis 1/3-1/4 mm distantibus, saepe indistinctis, dentibus fere 0 ; operculo rotundato-elliptico, facie inferiore plano ; ascidia superiora parva, e basi infundibuliformi parte inferiore paulum ventricosa, medio leviter angustata, os versus paulum infundibuliformia, costis 2 prominentibus, peristomio operculum versus acuto, cylindrico, 1/2-1 mm lato, costis 1/3-1/4 mm distantibus, saepe indistinctis, dentibus fere 0 ; operculo orbiculari v. rotundato-elliptico facie interiore plana ; inflorescentia racemus pedicellis 13-15 mm longis fere omnibus 2-floris ; indumentum in inflorescentiis et ascidiis parcum stellatum, ceterum 0.