3 Introduction to Taxons

Learning Objectives

  • Identify characteristics of taxons.


The plant family taxon is a grouping of plants consisting of one or more related genera that are more like each other than to other genera, and that includes the entire surviving lineage of the ancestral population. Family names always end with the suffix -aceae, except in a few notable cases where use of traditional names is also acceptable. Newer family names are based on the “type-genus” concept which means that for every family there is a genus that best represents the characteristics of the family. For example, Brassica (the cabbage genus) is the base for the family Brassicaceae, as is Rosa (the rose genus) for the family Rosaceae.


Older family names are still used since many are somewhat descriptive and may be more familiar than their newer counterparts. For example, Cruciferae (from the Latin crucifer, a cross) refers to the four-petal arrangement of flowers characteristic of the mustard family. The revised family names for some familiar plant groups are listed in Table 3.1.

Table  3.1:  Revised family names
Traditional Name New Name Common Name
Compositae Asteraceae Aster
Cruciferae Brassicaceae Mustard
Graminae Poaceae Grass
Labiatae Lamiaceae Mint
Umbelliferae Apiaceae Carrot


Because of new discoveries and technological advancements for determining plant genetics and other markers, some genera and family names have been reclassified under new names, as shown in Table 3.2. Updates to  plant information publications and online resources takes time and overlaps in established and reclassified family names can be expected.

Table 3.2:  Reclassified family names
Family Name Reclassified Name Common Name
Aceraceae Sapindaceae Soapberry
Asclepiadaceae Apocynaceae Dogbane
Taxodiaceae Cupressaceae Cypress


Taxonomic Example

The list of ten Pacific Northwest native conifers can be grouped into three families.  Within each family, there are a different number of genera, as represented by the common names. Within each genus, unless a monospecific (single) genus as with Taxus and Pseudotsuga, there are a number of different species.


Pinaceae – pine family

Douglas fir (Pseudotsuga, 1 species)

hemlock (Tsuga, 2 species)

larch (Larix, 3 species)

true fir (Abies, 3 species)

spruce (Picea, 4 species)

pine (Pinus, 7 species)


Cupressaceae – cypress family

arborvitae (Thuja, 1 species)

yellow cedar (Cupressus, 1 species)

juniper (Juniperus, 3 species)


Taxaceae – yew family

yew (Taxus, 1 species)