Part 1 – Plant Identification

2 Introduction to Taxonomy

Learning Objectives

  • Describe the scientific system of plant classification and naming.

A working knowledge of taxonomy is useful for classifying, naming, and identifying unknown plants. Theophrastus (370-285 BC), a Greek philosopher, first used taxonomy to describe and group plants according to their morphology (shape), growth, and reproductive traits. In the 18th century, a scientist named Carl Linnaeus applied binomials (two-term names) and classified known plants into a hierarchical system of classification.

Classification and Naming

The most effective classification systems are hierarchical and comprised of a nested series of categories or ranks. A good analogy is a computer filing system. Certain kinds of information reside at each level (drive, library, directory or folder, sub-directory, document, etc.), with file names (or labels) that signify the sort of information found there. Every level in the hierarchy is more inclusive than the one below it and the more of the filing system that is investigated, the more related information is uncovered.

Similarly, the categories used in plant classification provide an organizational framework into which the names of naturally occurring plants are slotted. In this framework, species of plants that are most similar to each other are grouped together. Groups or taxa (plural) are arranged in a hierarchical sequence of taxons (singular), from least inclusive rank at the bottom to most inclusive rank at the top as shown below in the plant classification hierarchy. In other words, the taxa “family” may include numerous plant genera, and within a genus (singular of genera) there may be any number of species, whereas within a given species, a subspecies may describe only a few populations or individuals.

Within taxa – family, genus, species, etc., there are identifiable characteristics common to each group. For example, plants in the cypress family typically have broad, flattened, scale leaves, while plants in the pine family exhibit needle-like leaves. Once organized into a sensible system that recognizes similarities or relatedness, the grouping becomes easier to understand and remember. That is, once characteristics for a given group are known, they can be used to match unknown plants with known taxons.

Plant Classification Hierarchy of Taxons

  • Family
  • Genus (plural = genera)
  • Species
  • Subspecies or Variety
  • Forma

Other Classification terms

  • Hybrid
  • Cultivar
  • Common Names
  • Plant Groups


Identify the hierarchy of plant taxons.



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Red Seal Landscape Horticulturist Identify Plants and Plant Requirements Copyright © 2020 by Michelle Nakano is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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