Evidence for monophyly of Alooideae is based on distinctive karyotype and characteristic leaf morphology.

The subspecies were separated from this variable species mostly by leaf morphology and distribution.

Identification is primarily by leaf morphology and flower color:

The leaf morphology may help it retain heat and increase photosynthesis, which is necessary because it grows at high elevations.

Nepenthes rajah is not generally considered to be closely related to any other species, due to its unusual pitcher and leaf morphology.

The terminology associated with the description of leaf morphology is presented, in illustrated form, at Wikibooks.

B. subcapitata most closely resembles B. yunnanensis but differs in both flower and leaf morphology.

Submersed individuals also have a different stem and leaf morphology from those that occur partially or completely out of the water.

The 11 genera are divided into four subfamilies, based on the cone, seed and leaf morphology:

Each of the main four populations varies from the others in their leaf morphology.