Editing Philodendron (section)

===Leaves===
[[File:PhilodendronMaximum.jpg|thumb|right|A leaf of ''[[Philodendron maximum]]'']]
The leaves are usually large and imposing, often lobed or deeply cut, and may be more or less [[pinnate]]. They can also be oval (''Philodendron'' 'White Princess'), spear-shaped, divided (''[[Philodendron tripartitum]]'') or in many other possible shape variations. The leaves are borne alternately on the stem. A quality of philodendrons is that they do not have a single type of leaf on the same plant. Instead, they have juvenile leaves and adult leaves, which can be drastically different from one another. The leaves of seedling philodendrons are usually heart-shaped early in the life of the plant. But after it has matured past the seedling stage, the leaves will acquire the typical juvenile leaf's shape and size. Later in the philodendron's life, it starts producing adult leaves, a process called [[metamorphosis]].<ref name="Ray">{{harvnb|Ray|1990|pp=1599–1609 }}</ref> Most philodendrons go through metamorphosis gradually; there is no immediately distinct difference between juvenile and adult leaves.<ref name="Bell">{{harvnb|Bell|Bryan|2008|p=26 }}</ref> Aside from being typically much bigger than the juvenile leaves, the shape of adult leaves can be significantly different. In fact, considerable taxonomic difficulty has occurred in the past due to these differences, causing juvenile and adult plants to mistakenly be classified as different species.

The trigger for the transformation to adult leaves can vary considerably. One possible trigger is the height of the plant. Secondary hemiepiphytes start off on the dark forest floor and climb their way up a tree, displaying their juvenile type leaves along the way. Once they reach a sufficient height, they begin developing adult type leaves. The smaller juvenile leaves are used for the darker forest floor where light is in scarce supply, but once they reach a sufficient height in the canopy the light is bright enough that the bigger adult leaves can serve a useful purpose. Another possible trigger occurs in primary hemiepiphytes. These philodendrons typically send their aerial roots downward. Once their roots have reached the ground below, the plant will begin taking up nutrients from the soil, of which it had been previously deprived.<ref name="Orihuela1">{{harvnb|Orihuela|Waechter|2010|pp=119–122 }}</ref> As a result, the plant will quickly morph into its adult leaves and gain in size dramatically. Another quality of philodendrons leaves is they are often quite different in shape and size even between two plants of the same species. As a result of all these different possible leaf shapes, it is often difficult to differentiate natural variations from [[morphogenesis]].