Organization of the collection

The collections are arranged by family number according to the most recent evolutionary understanding (see separate lists of families and family numbers). The flowering plants are arranged according to the Angiosperm Phylogeny Group III classification system. Within families, genera and species are organized alphabetically. Within species, specimens are grouped by region in colored folders, as indicated below.

Within species, specimens are grouped in color-coded folders by region, as follows:

Yellow - Arizona
Pink - United States (excluding Arizona), Canada & Greenland
Green - Mexico and the remainder of the Americas, including Caribbean Islands
Brown - Old World
White - Cultivate specimens, regardless of region

Exceptions are noted prominently at the appropriate locations in the herbarium.

In addition to the regular collection, types are stored separately, as is the boxed collection of large fruits and cones. There is also a collection of seeds, and small holdings of bryophytes and lichens.