Trematolobelia kaalae grows to a height of 1.2–2.1 meters. The stem measures 1–1.3 cm in diameter, glabrous, with semi-circular, shallowly obtriangular, or widely obtrullate cicatrices measuring 2.5–4.5 mm tall and 3.5–5 mm wide. The leaves are simple and alternate, forming a dense spherical, oblate, or cylindrical apical rosette. The blades are oblanceolate, measuring 15–19 cm long and 1.6–2.3 cm wide, with a length-to-width ratio of 9–10. The leaf apex is acuminate, and the base is attenuate, sometimes appearing petiole-like. The surfaces are glabrous, and the blades are coriaceous, with crenulate margins. Stipules are absent. The flowers are arranged in glabrous racemes, each with 25–30 flowers. The peduncle is 10–15 cm long, with sterile bracts that are oblanceolate, narrowly elliptic, or linear, measuring 30–120 mm long and 4–16 mm wide, with crenulate or entire margins and acuminate apex. The rachis is 14–26 cm long, with floral bracts that are narrowly oblong or linear, measuring 15–35 mm long and 3–4.5 mm wide, with crenulate or subentire margins and acute apex. The pedicels are 20–26 mm long, and oblong or elliptic bracteoles are 2–3 mm long. The hypanthium is hemispheric, measuring 5–7 mm long and 6–8 mm in diameter, 1/12–1/10 the length of the corolla. The calyx lobes are triangular, oblong, or ovate, erect, measuring 4.5–7 mm long and 1.8–2.8 mm wide, 2/3 the hypanthium length to equaling it, with entire margins and obtuse or acute apex. These flowers are tetracyclic, bisexual (perfect), protandrous, zygomorphic (bilaterally symmetric), epigynous, pedicellate, resupinate, and ornithophilous. The calyx is synsepalous, with a glabrous tube adnate to the ovary, forming a hemispheric, campanulate, oblate, obovoid, ovoid, or ellipsoid appendicular hypanthium 1/12–1/6 the length of the corolla. The corolla is subbilabiate and pink, measuring 70–73 mm long. The tube is gently curved, measuring 34–40 mm long, 4–7 mm tall at the middle, and 3–5.5 mm at the mouth. The dorsal lobes measure 31–37 mm long and 1–2.2 mm wide, with an acuminate apex. The ventral lip is obovate or widely elliptic, measuring 27–32 mm long and 4–8 mm wide. There are five stamens, antisepalous, connate distally for most of their length. The staminal column is strongly exserted, emerging above the dorsal lobes. The filament tube measures 57–62 mm long, 3.7–4.3 times longer than the dorsal anthers, and is sparsely to densely pubescent toward the apex. The anther tube measures 3–3.8 mm in diameter and is pubescent at the base. The dorsal anthers measure 14–16 mm long, and the ventral anthers measure 10–12 mm long, with tufts of white trichomes measuring 1.5–2.5 mm long at the apex. The ovary is inferior, 2-loculed, adnate to the hypanthium, and flat at the apex. The placentae are axile, with numerous ovules. The style is slender and cylindrical, with a ring of stiff white hairs near the apex. The stigma is 2-lobed, with the lobes appressed and non-receptive as the style grows through the anther tube, pushing out pollen, after which the stigmas spread and become receptive. The fruit is a broadly depressed oblate capsule measuring 7–10 mm long, 11–12 mm wide, and 7–9 mm thick. Numerous pores scatter the entire lateral surface. The seeds measure approximately 1 mm long and 0.4–0.9 mm wide. It is found in montane wet shrublands between 1,160-1,225 meters.