Hemiepiphytic vine or occasionally terrestrial; internodes elongate, 3-20 cm long, but much shorter on plant high on tree, to 3 cm diam., weakly glossy, dark green with sparse, coarse, short whitish streaks, especially at upper end; cataphylls yellow-green or green, sometimes tinged red, unribbed on younger plants, becoming sharply D-shaped, margins briefly flaring or prominently erect, 12-16 cm long, persisting semi-intact at upper nodes, soon decaying to thin, pale fibers; juvenile petioles 25-35 cm long, 2-3 mm diam.; petioles (35-) 46-55 cm long (averaging 53 cm), 3-5 mm diam. at middle, terete above base, with an obtuse medial rib beyond middle, or obtusely flattened adaxially; juvenile blades 17-28 cm long, 7-13 cm wide, with anterior lobe 15-20 cm long, 6-12 cm wide, with posterior lobes often unequal, 2-10 cm long, 3-5 cm wide, usually directed outward, with sinus 2-7 cm deep; adult blades narrowly ovate-triangular, narrowly acuminate at apex, cordate-sagittate at base, (26-) 40-46 cm long, 12-25 cm wide (averaging 46 X 23 cm), 1.7-2.3 times longer than broad, 0.7-1.0 times length of the petioles, broadest near point of petiole attachment, subcoriaceous to thinly coriaceous; upper surface dark green and matte-velvety; lower surface slightly to moderately paler and semiglossy to moderately glossy; anterior lobe (18-) 27-36 cm long; posterior lobes often markedly unequal, 9-18 cm long, 7-12 cm wide, directed outward or inward on adult plants; sinus parabolic to spathulate, occasionally V-shaped, 8-18 cm deep, 4-7 cm wide; midrib sunken or flat and paler green above, convex and paler below; basal veins 4-7 pair, 1-3 pair free to base, the remainder coalesced for 2-8 cm, narrowly sunken above, convex below; posterior rib naked for 1-4 cm; primary lateral veins 10-12 per side, departing midrib at 70°-90° angles, concave to narrowly sunken and concolorous above, round-raised to convex and matte below; minor veins visible but moderately obscure; INFLORESCENCES 1-2 per axil; peduncle white 14-15 cm long, 4-6 mm diam. on drying; spathe 13-14.5 cm long, 3 cm diam. furled, flattening to ca. 5 cm wide, the dark maroon on tube (both surfaces); blade flattening to 6 cm wide, green tinged maroon on blade yellow-green at tip and along open margin, otherwise heavily tinged maroon, inner surface reddish-violet except at apex, whitish at apex; spadix 10.7-11.5 cm long, pistillate portion, pale green, 2.1-3.7 cm long in front, ca. 1.3-2 cm long in back, 1.2 cm diam. midway; staminate portion 5.5-7.4 cm long, sterile staminate portion 0.7-2.2 cm long, 0.7-1.1 cm diam.; staminate flowers 0.9-1.2 mm long, 0.8-1.5 mm wide; sterile staminate flowers 1.5-2.2 mm long, 0.6-1.1 mm wide; pistils 1.1-1.2 mm long, 0.6-0.7 rom diam.; locules 4 per ovary; ovule 16-20 per locule.
Philodendron narinoense is known only from the type locality Colombia (Narino) and adjacent place Ecuador (Carchi), at elevations of 1,780-2,275, in Premontane wet forest life zone. It is apparently moderately common at La Planada, having been collected in the area of regrowth forest along the trail leading up to the ridge from La Posada and along Sendero Vieja, along the ridge top in the direction of La Pina.