Blades of P. subg. Philodendron in Central America as elsewhere are highly variable in size but relatively few have blades that are considered huge. Only 19 Central American species of P. subg. Philodendron have blades that exceed 75 cm long (although many others approach that size). Of these, only P. gigas regularly exceeds one meter in length, with the maximum recorded at 137 cm. Philodendron ferrugineum rarely exceeds one meter in length. Alternatively, 53 species have leaves that exceed 50 cm in length. By the same token few species in Central America have small leaves. Only 37 species have blades which are less than 25 cm long on adult plants and of these only 13 have blades less than 15 cm long. Philodendron brewsteriense, with blades a maximum of 11 cm long, is the species with the smallest leaves and P. chirripoense, with blades up to 11.6 cm long, is about as small. Thus the median-sized leaf for Philodendron in Central America is 57 cm long. The broadest blades belong to P. gigas and P. radiatum (to 90 cm long) but P. pterotum (to 84 cm wide), P. findens (to 70 cm wide), P. dodsonii (to 66 cm), P. schottianum (to 64 cm) and P. warszewiczii (to 62 cm) have quite broad blades.
While blade size on Philodendron is often not reliable for taxonomic separation and even blade shape is sometimes unreliable, the length-width ratio is, in general, more acceptable as a taxonomic character. Blades range from being much broader than long, to more than eight times longer than wide in (P. cretosum) to broader than long. Blades are broader than long in a number of species, only 0.62 times as long as broad in P. anisotomum and P. brunneicaule and 0.7 times as long as broad in P. cotobrusense, P. grayumii, 0.74 for P. microstictum and P. pterotum. Other species with blades that may be sometimes broader than long include P. dressleri, P. hederaceum (both just barely), P. grandipes, P. jefense, P. lazorii, P. schottianum, P. thalassicum (rarely so), P. tysonii, P. warszewiczii, and P. wilburii. The average minimum blade length-width ratio for species with simple, unlobed leaves is 1.6 times longer than wide while the average maximum length-width ratio is 2.5 times longer than wide. There are slight differences with blade length-width ratios by section. Species in Philodendron sect. Calostigma have average minimum length-width ratios of 1.8 times longer than wide and an average maximum length-width ratio of 2.7 times longer than wide. Alternatively P. sect. Philodendron have average minimum length-width ratios of 1.4 times longer than wide and average maximum length-width rations of 2.2 times longer than wide. This is an indication of the fact that more members of P. sect. Calomystrium have oblong blades.
Blade margins are typically entire on simple leaves, never toothed and only rarely sinuate, such as in P. subincisum. Species which are weakly sinnuate are P. basii, P. dwyeri, P. jefense. On the other hand, blade margins are frequently undulate to a certain extent, especially on larger blades. Species which have broadly undulate leaves are P. annulatum, P. antonioanum, P. copense, P. ferrugineum, P. fortunense, P. grandipes, P. hebetatum, P. panamense, and P. sulcicaule.
Blade margins are frequently hyaline and also often weakly revolute. Species with hyaline margins include P. advena, P. crassispathum, P. davidsonii P. ferrugineum, P. gigas, P. immixtum, P. hederaceum, P. smithii, P. squamicaule, P. straminicaule, P. subincisum, and P. wilburii var. longipedunculatum.
The coloration of blades is highly variable and largely dependent on the habitat, but some species such as P. roseospathum, P. scalarinerve, and P. tysonii have very dark green blades while P. lazorii has lighter green blades. The upper surface of blades is invariably darker green than the lower surface (Fig. 64). A few species, such as P. chiriquense have purple coloration on young leaf blades but most lose this coloration in age. Exceptions are P. verrucosum which have adult blades generally purplish on the lower surface. A few species such as P. ligulatum var. heraclioanum (Fig. 274) and P. sagittifolium have leaf blades purplish-spotted on the lower surface, especially when young. Coloration of lower blade surfaces is more common to be restricted to the major veins which are frequently reddish (along with the young petiole) as, for example in P. antonioanum.