Typically the peduncle is terete but the peduncles may be somewhat flattened laterally, especially when there are clusters of inflorescences per axil. The peduncle is usually whitish or pale green at the base where it is often hidden by the leaf sheath. The remaining portion of the peduncle is usually dark to medium green with the surface often shortly pale-lineate like the petioles. The peduncle is often coarsely pale-ribbed near the apex, as in P. copense, P. dodsonii, P. findens and others, Rarely is the peduncle pinkish red as in P. malesevichiae or P. schottianum or reddish as in P. roseospathum (or sometimes in P. sulcicaule) or tinged with red or purple as in P. chiriquense, P. davidsonii var. bocatoranum, P. heleniae, P. grandipes, P. purpureoviride, and P. verrucosum.
Most peduncles, like other parts of the average Philodendron are glabrous, but some species have peduncles which are a conspicuously covered with trichome-like glands, e.g. P. squamicaule (Fig. 384), P. squamipetiolatum (Fig. 388), and P. verrucosum (Fig. 440).
The peduncle is usually much narrower than the spathe, commonly no more that 1/3 to 1/4 the width of the spathe tube and it is almost always broadened at the apex, merging almost imperceptibly with the spathe tube. Usually the color distinction is also gradual but in some cases, e.g., P. annulatum, P. dodsonii, and P. dolichophyllum, there is an abrupt transition between the green peduncle and the colored spathe. In P. ligulatum there is a purple ring at the apex of the petiole, much like that at the apex of the petiole (Fig. 276).
The relative length of the peduncle, especially compared to the relative length of the spathe, may be important taxonomically. Some species, e.g., P. antonioanum, P. crassispathum, P. davidsonii, P. ferrugineum, P. findens, P. malesevichiae, P. purulhaense, P. radiatum, P. schottianum, and P. zhuanum have very short peduncles in relation to the length of the spathe. In contrast other species, e.g., P. advena, P. angustilobum, P. dodsonii, P. hebetatum, P. heleniae, P. immixtum, P. mexicanum, P. pterotum, P. rothschuhianum, and P. wilburii var. wilburii, have peduncles as long as or longer than the spathes.
Peduncles range in length from 1 to 25 cm with four species, P. microstictum, P. pseudoauriculatum, P. wilburii var. longipedunculatum, and P. verrucosum all having peduncles which attain the maximum length of 25 cm. Several additional species have peduncles which may be more than 20 cm long. These include P. anisotomum, P. brunneicaule, P. panamense, P. pseudoauriculatum, P. rothschuhianum, and P. scalarinerve. Only 16 additional species have peduncles which normally attain lengths of greater than 15 cm. These include P. advena, P. anisotomum, P. clewelii, P. cotonense, P. dodsonii, P. dressleri, P. hederaceum, P. heraclioanum, P. jacquinii, P. lazorii, P. ligulatum, P. mexicanum, P. sagittifolium, P. straminicaule, P. tripartitum, P. wilburii var. wilburii.
Most species of P. subg. Philodendron have peduncles which are more than 10 cm long. In addition to those mentioned above, 37 Central American species have peduncles more than 10 cm long. In contrast 38 taxa (35 species) have peduncles that are less than 10 cm long. Sixteen species have petioles which may be less than 3 cm long but only P. knappiae has a peduncle which does not exceed 3 cm in length.