Usually hemiepiphytic, rarely terrestrial or epilithic; stem usually appressed-climbing, thick, short, leaf scars inconspicuous; internodes striate, 2-3.5 cm long, 1-2.5 cm diam., about as long as broad, dark green to olive-green; roots drying tan to brownish red to blackish, smooth, elongate, 7 - 28 cm long, 0.2 - 0.5 cm diam., usually few per node, rarely numerous per node, dense, spreading at the nodes, epidermis peeling; cataphylls membranous, 28 - 31 cm long, 8 cm broad at base, usually unribbed, sometimes bluntly or sharply 1-ribbed to sharply 2-ribbed, green, red or purplish green, pale white-striate, drying brownish to reddish brown, persisting intact, eventually fibrous. LEAVES ± erect; petioles 29-107 cm long, 2-11 mm diam., erect, ± terete, stiff, firm, dark green, sometimes somewhat flattened with a low medial rib adaxially, surface weakly semiglossy, weakly light green striate with many small, fine ridges; geniculum thicker than petiole, 3 - 4 cm long, scurfy, slightly paler than petiole; blades ovate to ovate-triangular with prominent posterior lobes, chartaceous to subcoriaceous, moderately bicolorous, narrowly acuminate, sometimes long-acuminate at apex (the acumen inrolled, 1-4 mm long), cordate at base, 31-78 cm long, 16-52 cm wide (1.2-3.1 times longer than wide), (0.6 - 1.4 times longer than petiole), margins weakly undulate, upper surface gray-green to dark green, glossy, lower surface semiglossy, paler; anterior lobe 30.5 - 60 cm long, 14 - 34 cm wide (1.5 - 3.8 times longer than posterior lobes), broadest at point of petiole attachment; posterior lobes 10 - 29.5 cm long, 6 - 16.5 cm wide, broadest at or near the middle, directed downward and outward, sometimes inward, obtuse to sub-rounded to bluntly acute; sinus triangular, acute to almost obtuse, sometimes closed, 4.5 - 17 cm deep; midrib flat to sunken, concolorous to slightly paler than surface above, raised, concolorous, drying somewhat paler than surface below; basal veins 5 - 7 per side, with 0(1) free to base, part of the remainder coalesced 2 - 10.5 cm; posterior rib not naked; primary lateral veins (6)8 - 14(20) per side, departing midrib at a 65-90¡ angle, ± straight or weakly arcuate to the margins, prominently to narrowly sunken above, raised to convex below; inter-primary veins as conspicuous as primary lateral veins, weakly sunken and concolorous above, weakly raised and concolorous below; minor veins moderately visible to distinct below, arising from both the midrib and primary lateral veins. INFLORESCENCES erect, to 4 per axil; peduncle 2-11 cm long, 3 - 18 mm diam., pale green, drying reddish brown, heavily white-lineate, drying longitudinally fissured; spathe erect to erect-spreading, coriaceous, acuminate at apex, 7 - 14 cm long, (1.3 - 4.4 times longer than peduncle), moderately constricted above the tube, 2.1 cm diam. at constriction, short-lineate throughout; spathe blade weakly lanceolate, greenish white, sometimes heavily tinged red outside, 4 - 8 cm long, 2.1 cm diam., (opening 3.6 cm long), white to pale green inside; spathe tube ovoid, medium to dark green, usually tinged red or sometimes dark violet outside, white-striate with clear margins in front, short, pale green lineate in back outside, 3-7 cm long, 2-3.5 cm diam., white to pale green, sometimes red at base inside, sometimes sparsely white-spotted; spadix sessile; 6-12 cm long; pistillate portion yellowish green to pale green, weakly tapered upward, 2.8^4 cm long in front, 1.9 - 2.2 cm long in back, 1.1 - 1.6 cm diam. at middle, 1.75 cm wide at base, 0.9 - 1.5 cm ca. 1 cm from apex, with 12 - 14 flowers per spiral; staminate portion 5.3 - 7.1 cm long; fertile staminate portion white, drying orange reddish to light reddish, 1 - 1.1 cm diam. at base, 1.2 - 1.5 cm diam. at middle, 7 - 10 mm diam. ca. 1 cm from apex, broadest in the middle, as broad as to slightly broader than the pistillate portion, as broad as to narrower than the sterile portion, 27 - 35 flowers visible per spiral; sterile staminate portion as broad as to broader than the pistillate portion, pale brown, 11 - 17 mm diam.; pistils 2.7 - 3.1(6.2) mm long, 1.2-1.7(3.9) mm diam.; ovary 4 - 5-locular, 1.6-2(5.9) mm long, 1.2 - 1.7(3.9) mm diam., with axile placentation; locules 1.6-2(4.2-5.9) mm long, 0.4 - 0.7(1.1) mm diam.; ovules 12-14 per locule, 2-se-riate, 0.4 mm long, longer than funicle; funicle 0.2(0.5) mm long, adnate to lower part of partition, style 0.5 - 0.6 mm long, 1.2 - 1.7 mm diam., similar to style type B; style apex flat; stigma cupullate, ± hemispheroid, 1.1 mm diam., 0.4-0.6 mm high, covering center of or entire style apex, depressed medially with 6 - 8 holes; the androecium truncate, prismatic, margins irregularly 4 - 6-sided, (0.3)0.7 - 0.9 mm long, 1.1 - 1.4 mm diam. at apex; thecae oblong, 0.3-0.4 mm wide, ± parallel to one another, nearly contiguous; sterile staminate flowers irregularly 4-6-sided, mostly prismatic, sometimes clavate, blunt, 1.3 - 2.5 mm long, 1.4 - 2.5 mm wide. INFRUCTESCENCE with fruits purplish.
In Central America it occurs in Premontane wet forest, rarely in Tropical moist forest. Philodendron tenue is ecologically quite versatile in South America, where it occurs in Tropical thorn woodland, Premontane thorn woodland, Tropical dry forest, Tropical moist forest, and Premontane wet forest life zones.