Taxonomy

Why is Taxonomy Important?

Taxonomy involves the classification and relationships of plants, often referred to as systematic botany. This field is essential due to the vast diversity of plant life, with over 500,000 living species identified. Even the most skilled taxonomists may only recognize around 5,000 species.
Various classification systems have been developed over time. For instance, Pliny (A.D. 23-79) categorized plants based on their size and form, creating three main groups: herbs, shrubs, and trees. In the Middle Ages, plants were classified according to their uses, such as medicinal, edible, or poisonous. The renowned Swedish botanist Linnaeus (1707-1778) introduced a system based on the number of stamens, which were viewed as reproductive organs. Some of his contemporaries found this approach controversial. These classification systems are often seen as artificial, as they are based on arbitrary criteria.
In contrast, a natural classification system is grounded in the actual relationships among plants. This means that similar plants are grouped together based on their true connections. Typically, simpler plants are listed first, followed by more complex ones, reflecting the principles of evolution. Natural classification systems have emerged more recently, shaped by the extensive research and insights of generations of botanists.

Definition of Terms

Taxonomy is the study of the general principles of scientific classification, especially, orderly classification of plants and animals which best reflects the totality of their similarities and differences.
Taxonomic groups of the plant kingdom are: Kingdom > Division > Subdivision > Class > Subclass > Order > Family > Genus > Species.
In aromatherapy it's enough to know: Family > Genus > Species
The genus: generic names are based on structural characteristics and are always written in italics with an initial capital letter and can be used alone
The species: these are adjectival describing the genus and are never written with a capital letter, even when it is after a person e.g. smithii the whole word is in lower-case italics and cannot be used by itself.
Exemple: German Chamomile = Matricaria recutita L.
Subspecies: often denotes a geographic variation of a species.
Exemple: Eucalyptus Australiana = Eucalyptus radiata Sieber ex DC. subsp. radiata
Variety: indicates a rank between subspecies and forma. They are named by adding ‘var’. The label ‘var.’ is used to indicate a major subdivision of a species, or a variant of horticultural origin or importance (although these are now labelled cultivar). Many names of horticultural origin reflect the historical use of the variety rank.
Exemple: Tagetes = Tagetes minuta L. var. bipinata
Forma: denotes trivial differences.
Cultivar: indicates a cultivated variety, and a rank known only in horticultural cultivation. These names are non-Latinized and in living languages (usually the name of, or chosen by, the originator, in the following case Monsieur Maillette). They are not italicized, and appear within quotation marks.
Exemple: English lavender 'Maillette' = Lavandula angustifolia Mill. 'Maillette'
Chemotype: indicates visually identical plants but having different, perhaps significantly so, chemical components, resulting in different therapeutic properties. Chemotypes occur naturally in plants grown in the wild, some species throwing up many chemical variations; they can be propagated by cuttings for cultivation and they are named by the abbreviation ‘ct.’ followed by the chemical constituent, e.g. Thymus vulgaris ct. thujanol-4, T. vulgaris ct. geraniol, T. vulgaris ct. carvacrol, etc. Chemotypes are plants that look the same from the outside, but have different chemical constituents inside; by contrast phenotypes are plants that look different on the outside but are chemically similar inside.
Exemple: Thyme ct. thujanol = Thymus vulgaris L. ct. Thujanol
Hybrid: indicates natural or artificially produced crosses between species. The name contains ‘x’ (in Roman font) which means the plant is a hybrid produced by sexual crossing e.g. Mentha x piperita, which is a cross between Mentha aquatica and Mentha spicata.
Exemple: Key Lime = Citrus × aurantiifolia (C. hystrix × C. medica) (Christm.) Swingle