Epiphytic or hemiepiphytic vine; internodes dark green, becoming gray, weakly glossy to semiglossy, 2-15 cm long, 1.5-1.8 cm diam., drying with a thin, loose, tan epidermal layer; eataphylls green, tinged reddish, moderately thin, unribbed to bluntly I-ribbed, to 5 cm long, drying red-brown, deciduous; petioles 5-12 cm long (averaging 8.9 cm), 4-6 mm diam. at middle, erect-spreading, obtusely much flattened adaxially; blades ovate, ovate-elliptic, oblong-elliptic, or oblong, acuminate at apex, acute, obtuse, broadly rounded, tmncate, or even weakly cOl·date at base, 19-39 cm long, 6--15 cm wide (averaging 27.9 X 10 cm), 2.6-3.0 time longer than broad, 3.2-4.3 times longer than the petioles, surfaces semiglossy, moderately bicolorous, subcoriaceous; anterior lobes 16-35 cm long, posterior lobes not equal, to 3.5 cm long, 4-5 cm wide; midrib flat to obtusely and weakly sunken and scarcely to slightly paler above, narrowly rounded to thicker than broad and darker below; primary lateral veins 6--8 per side, weakly and narrowly sunken above, weakly convex and darker below; minor veins obscurely visible; INFLORESCENCES to 5 per axil; peduncle 3-8.5 cm long, 1-2 mm diam., green; spathe 4-6 cm long; spathe tube light green to whitish inside, medium green outside; spathe blade white inside, tinged red near apex (post-anthesis), pale green to white outside; spadix 3-4 cm long, cylindroid; pistillate portion medium green, 2.0-2.5 cm long, 3-5 mm diam.; staminate portion white or pale reddish to pink at anthesis, 2.5-3.0 cm long, 4-5 mm diam.; pistils 2.8 mm long, 1.8-2.4 mm diam.; style about as wide as the pistil, quadrangular to rounded or pentagonal, the margins thicker and raised, the center sunken with the medial stigma button-shaped, 0.4 mm diam.; ovules 1 per locule with basal placentation; seeds 1.9-2 mm long, 0.8 mm diam., appearing to be attached to the lower surface of the style, terete in cross-section, light brown, moderately smooth.
Stem scandent, upper internodes up to 10 cm long, 1.5-2.0 cm ('1,5-2 dm') thick. LEAVES: Petiole subterete, 18-25 cm long, sheathed for 3-5 cm at the base, thereafter terete. Blade herbaceous, base cordate, oblong, 25-30 cm long, 10-14 cm wide; 2-3 primary lateral veins borne at the base, 4-5 emerging from the midrib at an angle of ca. 80º, slightly arcuate near the margin, 2-3 slender secondary veins interjected between the more slender parallel primary veins. INFLORESCENCE: Several peduncles 2-2.5 cm long. Spathe oblong, very slightly constricted halfway, 4-5 cm long, convolute, 6 mm wide. Spadix shortly stipitate, cylindroid, obtuse, ca. 4 cm long, 4 mm thick. Female zone somewhat shorter than the male zone. Pistils oblong, 1.5 mm long, stigma small, rounded, locules 1-ovulate. Stamens barely longer than broad, thecae oblong, obtuse at both ends.
Philodendron oligospermum ranges from southern Colombia (Huila, Narino, Valle del Cauca) to central Ecuador (Bolivar, Canar, Carchi, Chimborazo, Cotopaxi, El Oro, Imbabura, Manabi, Zamora-Chinchipe, Pichincha) and Peru (Huanuco), at elevations of 250-2,200 m, primarily above 1,400 m, in Tropical dry forest, Premontane wet forest, Lower montane dry forest, Lower montane moist jorest, Lower montane wet forest, and Montane moist forest life zones.