Usually hemiepiphytic, sometimes epiphytic; stem appressed or climbing; sap brown with fruity odor; internodes 3–25 x 1–3 cm, longer than broad, medium brown to reddish brown; epidermis scurfy to deeply reticulate-fissured appearing corky, drying medium brown and deeply reticulate-fissured; roots few per node, drying red-brown with flaky epidermis; cataphylls to 20 cm, unribbed to sometimes 2-ribbed near apex, bluntly rounded at apex, medium green, tinged red or purple-spotted at base, drying reddish brown with paler margins, becoming soft with thin brown epidermis, then deciduous. LEAVES spreading; petioles 42(–58) cm x5–10 mm (dry), terete, medium green, firm, obtusely to broadly sulcate at base, weakly striate at apex, drying dull dark olivegreen with many longitudinal wrinkles; geniculum striate, to 5 cm, usually drying dark brown to black, often wider than petiole; blades ovate-elliptic to ovate, coriaceous, acuminate at apex, cordate at base, rounded along margins, 29–54 x 12–37 cm, 1.3– 1.8(–2.4) x longer than wide, 0.9–1.2(–2.1)xas long as petiole; adaxial surface moderately glossy, dark green, drying glossy pale gray-green; abaxial surface matte, paler than adaxially, drying dull and barely paler than adaxial surface; anterior lobe 39.5–46 x 37 cm, 4.2–6.6(–8.1) cm longer than posterior lobes; posterior lobes 5–10.5 x 7–11.5 cm; sinus arcuate to parabolic, 1.3–6 cm deep; midrib flat, medium green adaxially, convex and sometimes purple-spotted abaxially; primary lateral veins 14 to 20 per side, spreading from midrib at 60º–75º angles, downturned at midrib, 5 mm apart near base widening to 4 cm apart near apex; basal veins 6 to 8 per side, all free to base; minor veins distinct; all veins drying concolorous and sunken adaxially, darker than blade or sometimes paler than blade and raised abaxially. INFLORESCENCE erect to spreading, 3 to 6(to 10) per axil, often enclosed in a persistent pink prophyll that dries reddish brown; peduncle 3–10.5 cm, 3– 5 mm diam. (dry), much shorter than petiole, pale green, sometimes faintly striate, drying dark brown, moderately flattened; spathe 5.5–11 cm, rounded and slightly apiculate at apex, barely constricted above the tube, margins and apiculum white, drying dark to medium brown, sometimes reddish brown; spathe blade brick to cherry-red, sometimes with purple ringlike or pale spots, or green speckles outside, creamy white with orange resin canals in lower 2/3 inside; spathe tube pale green at base, upper part tinged red to cherry-red, sometimes pale spotted outside; spadix exserted from spathe at anthesis, clavate, 7.4–8.5 cm; pistillate portion yellow-green becoming pink, 1.5– 3 cm, 8–10 mm diam. at base (dry), 6–8 mm diam. at point where it meets the staminate portion (dry); staminate portion creamy white, 4–5.5 cm, somewhat constricted above the pistillate portion; fertile staminate portion clavate, 4.5–5 cm x 5–7 mm at base, 8–12 mm wide 1 cm from apex; sterile staminate portion not obvious; pistils ca. 1.5 x 1.6–2 mm; ovary 6- to 7-locular, ovules with subbasal placentation, 2 to 3 per locule; sterile staminate flowers ca. 4 x 9–10 mm. INFRUCTESCENCE unknown. JUVENILE PLANTS differ in having ecordate, broadly elliptic leaf blades.
The species is a member of subgenus Philodendron, section Macrobelium, subsection Macrobelium, series Macrobelium and is characterized by its reticulate-fissured stem internodes with a corky appearance for which it is named, from the Latin ‘‘suber’’ or cork (cork tree); elliptic to barely cordate blades with basal veins that do not coalesce; primary lateral veins becoming wider apart toward the apex; and large clusters of inflorescences, with peduncles that are much shorter than the petioles, and with spathes that are pale green on the tube and have cherry-red blades. Philodendron suberosum is somewhat similar to P. trojitense Croat & D. C. Bay; however, that species differs in having stem epidermis that is only transversely fissured (not appearing corky), and blades that are longer and narrower (2–3.53 longer than wide) with fewer primary lateral veins consistently widely spaced (3–7.5 cm apart). In addition, the inflorescences are long-apiculate and pale yellow with red-violet spots, not solid dark red like P. suberosum. The only other Philodendron with which this species might be confused is P. discretivenium, but the latter species does not have a corky stem epidermis, the blades have coalesced basal veins, and the inflorescences have spathes that are greenish white on the tubes, with paler blades.