Taxonomy

TAXONOMY: the science of describing, naming and classifying plants or animals, following the International Code of Botanical Nomenclature for plants. A taxon (plural: taxa) is any taxonomic entity, of whatever rank.

Penstemons, because they number almost 300, are subdivided into six SUBGENERA, apparently natural groups, categorized by anther shape and method of opening. Each SUBGENUS is posted under the first column in the table below. They are further subdivided if needed into SECTIONS, then SUBSECTIONS in particularly large groups.

SUBGENUS DASANTHERA, 9 species, the most primitive; no other subdivisions are needed.

Two subgenera are monotypes, containing only one species:
SUBGENUS CRYPTOSTEMON: species: Penstemon. personatus
SUBGENUS DISSECTI: species: Penstemon dissectus.

SUBGENUS PENSTEMON, the largest with 8 SECTIONS and many Subsections.

SUBGENUS HABROANTHUS with 2 SECTIONS.

SUBGENUS SACCANTHERA with 2 SECTIONS.

Detailed documents linked below.