Planta hemiepiphytica; internodia 3.5--4 cm longa, ca. 1 cm diam.; cataphylla acute 2-costata, 15 cm longa, decidua; petiolus 8--9 cm longus, 7--8 mm diam., convexus adaxialiter cum 2 costis marginalibus; lamina oblongo-oblanceolata, debiliter cordata basi, 19--28 cm longa, 4--6 cm lata; nervis primariis lateralibus 5--6 utroque; inflorescentia 1; pedunculus 10.5 cm longus; spatha usque 15.7 cm longa, viridis; lamina spathae intus viridi; tubo spathae extus suffuso rubro, intus rubro; pistilla 3--5- locularia; loculi 1-ovulati.

Hemiepiphytic vine; internodes semiglossy, 3.5--4 cm long, ca. 1 cm diam., longer than broad, drying light brown, epidermis longitudinally deeply ridged, finely striate on magnification and densely granular to almost scabrous (but not harsh to the touch), the vestiture raised to ca. 1.5--2 times longer than wide; roots drying dark brown, <15 cm long, 1 mm diam., few per node; cataphylls 15 cm long, sharply 2-ribbed, (ribs low), green, deciduous.
LEAVES with petioles 8--9 cm long, 7--8 mm diam., convex with acute margins adaxially, drying dark brown and somewhat sulcate adaxially with distinct acute marginal rib; sheath short, inconspicuous, 1--2 cm long, for <0.25 its petiole length; blades oblong-oblanceolate, acuminate at apex, weakly cordate at base, 19--28 cm long, 4--6 cm wide (3.8--4.7 times longer than wide), upper surface medium green, weakly glossy, drying dark brown, lower surface slightly paler, drying yellowish brown; midrib flat, concolorous above, convex, slightly paler than surface below; basal veins 1--2 per side, with 1--2 pairs free to base, indistinct; primary lateral veins 5--6-per side, weakly sunken above, convex, slightly paler than surface, drying paler below; minor veins moderately obsure, barely visible on drying, the larger weakly undulate, arising from the midrib only, secretory canals appearing on magnification as short, pale raphide cells along the minor veins. INFLORESCENCES (Post-Anthesis), 1 per axil; peduncle 10.5 cm long, 1 cm diam.; spathe to 15.7 cm long, to 7 cm wide when flat, weakly constricted above the tube, green throughout; spathe blade green inside with prominent striations from lower 1.5 cm to 9 cm up from base; spathe tube tinged red outside, red inside; fertile staminate portion to 5.5 cm long, 9 mm diam.; spadix with pistils 1.5--3 cm diam., drying light brown, sparsely granular on the sides; ovary 3--5-locular; ovules with 1 per locule, style similar to style type E; style funnel 0.5--0.7 mm, distinctly raised above the surface. INFRUCTESCENCE 10 cm long, 2.7 cm diam. in lower 1/3, prominently tapered toward apex to 1.3 cm diam. at apex; berries whitish; seeds oblong-elliptic, tan, smooth, 1.3--1.9 mm long.

Flowering in Philodendron granulare probably occurs in the early wet season. Fruiting is recorded by a single collection made in July.

Philodendron granulare is known only from the Panamanian type specimen, from Darién Province near El Real along the Río Pirre at less than 75 m elevation in Premontane wet forest.

Philodendron granulare is a member of P. sect. Calostigma subsect. Glossophyllum ser. Glossophyllum. This species is distinguished by its scandent habit, more or less oblong, short-petiolate blades with subcordate bases, and especially by its densely granular dried stem (hence the name) and distinct funnel-shaped styles.

Philodendron granulare is most easily confused with P. bakeri which it resembles in a superficial way. The latter species differs in having totally smooth stems, petioles with conspicuous sheaths often extending to the middle or beyond, leaf blades with more conspicuous minor veins, and pistils with a truncate, type B style which lacks a funnel, having instead the stylar canals emerging directly onto the flat truncate apex.