Larsenianthus assamensis grows as an evergreen, herbaceous plant that can reach heights of up to 1.44 meters.

The dull green underside of the leaves is tinted blue-green and has a flat central rib.

[1] The stalked inflorescence is formed as a winding thyrsus at the tip of leafy shoots and can reach a total length of up to 14 centimeters.

In older inflorescences, an adventurous shoot can arise from the lower, sterile bracts.

The lanceolate-boat-shaped prophylls are about 2.7centimeters long and about 1.9 centimeters wide, are slightly translucent white and have a red, conical tip.

The between 0.8 and 0.9 centimeters long and 0.4 to 0.45 centimeters thick, elongated to elliptical shaped, white capsule fruits have a row of seeds in each half of the capsule, which are divided into a total of three separate chambers.

[1] Larsenianthus assamensis has so far only been found at two locations in Cachar, a district of the state of Assam in northeast India .

[1] It was first described as Larsenianthus assamensis in 2010 by Santanu Dey, John Donald Mood, and Suptotthita Choudhury in PhytoKeys number 1, page 26.

The specific epithet assamensis is reminiscent of the Indian state of Assam, where the species is endemic.