Appressed-climbing hemiepiphyte growing to 15 m in trees. JUVENILE plants appear scandent, growing as a semi-epiphytic vine with short internodes, 2.0-2.5 cm, with cataphylls drying reddish brown and intact, and with moderately spongy petioles flattened laterally, 9-17 cm long and blades 9-10 cm long. ADULT plants with elongate internodes, 3-35 cm long, 7-13 cm diam. on trailing portions, 2-5 cm diam. on flowering plants, grey-green to green, turning light to yellow brown, semiglossy; cataphylls green, unribbed, 18–26.5 cm long, turning reddish brown, then deciduous; roots 5-6 per node, light brown, to 25 cm long, 2.5 mm diam., later to 4 mm diam and less than 1 m long; LEAVES: petioles 56-90(100) cm to 1.8-2 times longer than blades, rarely equalling blade, terete with an obscure medial rib adaxially, weakly to obtusely flattened adaxially, firm (less spongy than young plants), dark green, semiglossy, faintly striate, sometimes spreading; midrib flat to broadly convex and concolorous above, convex to narrowly convex or in some bluntly angular, and concolorous below, slightly darker than surface; primary lateral veins 8-10 per side, concolorous, weakly sunken to quilted-sunken above, weakly pleated-raised to prominently convex and darker than below; minor veins moderately distinct to obscure below, fine, moderately close; blades deeply 3-lobed somewhat pendent from an erect-spreading petiole, slightly bicolorous, dark green above, moderately paler beneath, subcoriaceous, semiglossy, drying gray-green above, yellowish-reddish brown below; medial lobe more or less elliptic, 32–45(53) cm long, 8.5–20 cm wide, acuminate to weakly cuspidate at apex, ; lateral lobes slightly shorter than, but similar in shape to medial lobe, the upper edge attenuate at base, lower edge rounded at base, sinus of lateral lobes 14–39 cm, lower margins of medial and lateral lobes erect and confluent at apex of petiole. INFLORESCENCE 1 to 2 per axil; peduncle 6–10 cm long, 1.2 diam., green, spongy, faintly striate; spathe 10–17 (20) cm long, medium to yellow-green, densely pale-speckled especially toward apex, semiglossy outside, paler and glossier within, becoming pale yellow-green on tube at anthesis, white or pale greenish on tube within, burgundy in lower half, whitish on blade within; spadix to 16.5 (20) cm long, pistillate spadix cream to greenish, staminate spadix, clavate, white to pale green, 4.5–9.5 cm long 1.0–1.7 cm diam.; staminate spadix 5.5–10 cm long, 0.8–2.0 cm diam., sterile part ca. 7 mm long, sterile male flowers white.
Philodendron hylaeae is widespread in the northern and western Amazon Basin, ranging from Venezuela (Amazonas, Bolivar, Delta Amacuro) to the Ripuruni River in Guyana, southeastern Colombia (Amazonas, Caqueta, Guainia), Brazil (Amapá, Acre, Amazonas, Roraima), Ecuador (Napo, Orellana, Sucumbios, Zamora-Chinchipe), northern and eastern Peru.