Hemiepiphytic; stem appressed-climbing; internodes 3–6 cm x 5–10 mm, sometimes weakly flattened on one side, light yellow-green, epidermis semiglossy, drying smooth, reddish tan to red-brown; roots few at each node, smooth, drying dark brown; cataphylls 6–8.5 x ca. 1.5 cm, sharply 2-ribbed, rounded at apex, light yellow-green, drying reddish tan or red-brown, deciduous. LEAVES spreading; petioles 3.5–6 cm x 2–4 mm (dry), broadly and bluntly sulcate, light green, drying yellowish tan to reddish tan with loose wrinkled epidermis; blades elliptic, subcoriaceous, acuminate at apex, attenuate to truncate at base, 10–14.4 x 3.5–6 cm, 2–3x longer than wide, 1.9–2.5(–3.2)x longer than petiole; adaxial surface dark green, semiglossy, drying dull olive-green; abaxial surface pale yellow-green, drying reddish tan or reddish brown with minute red punctations; midrib broadly rounded (almost flat), paler than blade, drying light tan adaxially, narrowly rounded and paler abaxially, drying much paler; all other veins obscure on both surfaces. INFLORESCENCES solitary; peduncle terete, 6–9.2 cm x ca. 2 mm (dry), slightly longer than petiole, semi-glossy, light green, drying olive-green; spathe curved, apiculate, not constricted, 4.2–5.5 cm, uniform in width, 8–11 mm wide (dry), drying light reddish tan; spathe blade white to yellow outside; spathe tube yellow-green outside, spadix cylindrical, 4.2–4.4 cm; pistillate portion yellow, 1.8–2 cm, fairly uniform in width, 3–4 mm wide (dry); staminate portion 2–3.5 cm; sterile staminate portion 4–6 mm, slightly narrower than pistillate portion and fertile staminate portion; pistils 2–2.4 x 1.4–1.8 mm, ovary 5-locular, ovules with basal placentation, 2 per locule. INFRUCTESCENCE unknown.
Philodendron rubromaculatum is a member of subgenus Philodendron, section Macrobelium, subsection Glossophyllum, series Glossophyllum characterized by its appressed-climbing hemiepiphytic habit, deciduous cataphylls, and small elliptic blades that are pale yellow-green abaxially and dry reddish tan with red punctations (hence the epithet from the Latin ‘‘ruber’’ meaning red and ‘‘maculatus’’ meaning spotted). Also distinctive are its small, yellow-green inflorescences with yellow female flowers.
Philodendron rubromaculatum is somewhat similar to P. longipes Engler as they both have elliptic blades with obscure veins and small, slender, cylindrical inflorescences. However, P. longipes has much larger blades that are never punctate and dry light olive-green on both sides, cataphylls that persist at the bases, and inflorescences that are green on the spathe tube and yellow-green on the spathe blade, with green female flowers.
IUCN Red List category. Conservation for Philodendron rubromaculatum must be considered as Near Threatened (NT) according to IUCN Red List criteria (IUCN, 2001). There is no reason to assume that it is exceedingly rare because only a tiny fraction of the Bajo Calima region has been studied, but it has not been collected elsewhere from other sites in Colombia.