Plant Taxonomy BHT344

Learn how to classify and identify plants based on systematic analysis of differentiating plant characteristics. 

Learn about:

  • Botanical nomenclature
  • Plant classification
  • Plant parts and their use in plant identification
  • Plant description methods
  • Taxonomic techniques
  • Important plant families

Course Content

There are 10 lessons in this course:

1. Introduction to Taxonomy

  • Introduction to Plant Taxonomy
  • Scientific Vs. Vernacular Names
  • Linnaeus
  • Binomials
  • Uniformity
  • Protein Analysis
  • Ranks and Language
  • Ranks of Classification - KPCOFGS
  • Plant Phyla
  • Plant Families
  • Genus and Species
  • Latin Names
  • Gardener's Ranks
  • Hybrids
  • Subspecies
  • Varieties
  • Cultivars
  • International Code of Botanical Nomenclature
  • The Basic Ideas
  • Principle of Priority
  • Legitimate Naming
  • Recent Changes to the Code
  • International Code of Nomenclature for Cultivated Plants
  • Taxonomic Name Resolution Service
  • International Plant Names Index
  • Trademarks & Patents
  • Plant Breeders Rights
  • The Rise of Molecular Data
  • The Impact of Molecular Data

2. Describing Plant Parts

  • Habit
  • Stems
  • Hairs
  • Leaves
  • Compound and Simple Leaves
  • Leaf Shapes
  • Leaf Margins
  • Leaf Structure
  • Leaf Arrangements
  • Leaf Venation
  • Leaf Modifications
  • Roots
  • Root Modifications
  • Terminology
  • Flowers
  • The Inflorescence
  • Fruits
  • Dry Fruits
  • Fleshy Fruits
  • Compound Fruits
  • A Key to the Main Types of Fruits
  • Terminology

3. Recording & Analysing Plant Descriptions

  • Herbaria - Collecting and Preserving a Plant
  • Fresh Material
  • Arranging Plants for Pressing
  • Pressing Difficult Specimens
  • The Drying Process
  • Herbarium Specimens
  • Photographs
  • The Problem of Colour
  • The Law Relating to Plant Collecting
  • Describing a Plant on Paper
  • The Equipment You Need
  • Botanical illustration
  • Floral Diagrams
  • Floral Diagram Technique
  • Floral Formulae
  • DNA Barcoding
  • Process of Using DNA Barcoding for Plant Identification
  • Applications of DNA Barcoding
  • Chemical Analysis (Chemotaxonomy)

4. Taxonomic Techniques

  • The Advantages of Using Keys and Their Limitations
  • Using a Key
  • The Rules when Making a Key
  • Lamiaceae (Simplified Key)
  • Rules When Writing Couplets
  • Best Practice Points
  • Making a Key
  • Why Botanical Families are So Useful When Identifying Plants

5. Primitive Plants

  • The Bryophytes
  • Mosses
  • Liverworts
  • Hornworts
  • Vascular Plants or Tracheophytes
  • Vascular Tissue and Why it is Important in Evolution of Life on Earth
  • A glossary to help you
  • The Lycopodiopsida (or Lycophytes)
  • Clubmosses - Plants in the family Lycopodiaceae
  • Quillworts - Plants in the Family Isoetaceae
  • Spike Mosses or Lesser Clubmosses - Plants in the Family Selaginellaceae
  • The Euphyllophytes - The Seed Plants, Horsetails, and Ferns
  • The Seed Plants
  • Horsetails
  • The Ferns

6. Seed Plants

  • The Gymnosperms
  • The Cycads
  • Ginkgo
  • The Gnetidae
  • Welwitschiaceae
  • Gnetaceae
  • The Conifers
  • The Conifers’ Life History
  • The Cycads, Ginkgo, and Gnetidae - How they Differ from the Conifers
  • The Six Families of Conifers
  • The Angiosperms
  • Flowers and Why they are Important in Evolution of Life on Earth
  • The Flowering Plant’s Life History
  • The Diversity of Angiosperms

7. Phylogeny of Land Plants

  • Introduction
  • Darwin’s Tree of Life Metaphor - The Hidden Bond of Descent
  • Why Use DNA Sequences for Classification?
  • The Principle of Monophyly
  • The Phylogeny of Land Plants
  • The Major Changes in Flowering Plant Taxonomy
  • The End of the Monocot-Dicot Split
  • Finally, Some Resolution Within the Monocots
  • Some Surprises
  • Name Changes Resulting from the Increase in Evidence
  • When Applying the Principle of Monophyly Results in Name Changes
  • What We Can Learn From Phylogenies

8. Monocotyledons

  • Summary of Important Families
  • The Monocots - Significant Families
  • Arecaceae
  • Aizoaceae (syn. Ficoidaceae)
  • Dioscoraceae
  • Liliaceae
  • Orchidaceae
  • Iridaceae
  • Amaryllidaceae
  • Asparagaceae
  • Arecaceae
  • Pontederiaceae
  • Musaceae
  • Bromeliaceae
  • Poaceae
  • Cyperaceae
  • Juncaceae

9. Dicotyledons (Part I)

  • Important Dicot Families
  • Key to Selected Angiosperm Families
  • Lower-growing Soft-wooded Plants
  • Apiaceae
  • Asteraceae
  • Brasicaceae
  • Cactaceae
  • Crassulaceae
  • Euphorbiaceae
  • Gesneriaceae
  • Lamiaceae
  • Ranunculaceae
  • Solanaceae

10. Dicotyledons (Part 2)

  • Fabaceae - Papilionoideae, Mimosoideae, Caesalpinoideae
  • Fagaceae
  • Ericaceae
  • Magnoliaceae
  • Malvaceae
  • Myrtaceae
  • Ongaraceae
  • Rosaceae
  • Proteaceae
  • Rutaceae
  • Rubiaceae

Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.


  • Explain how plants are classified, including both benefits of and contradictions within the scientific system as followed by horticulturists and botanical scientists across different parts of the world.
  • Examine and describe parts of a plant, both sexual and asexual, at various stages of the plant’s life cycle.
  • Process descriptive information about a plant using taxonomic techniques that involve processing that data to create a better understanding and/or record of that information.
  • Explain a variety of tools used in taxonomic work.
  • Explain the taxonomy of land plants that do not produce seeds.
  • Explain taxonomy of a range of significant, seed producing plants, including gymnosperms.
  • Explain the relationship between different types of plants (i.e. phylogeny), and how molecular information impacts on this in taxonomic considerations.
  • Differentiate between at least 10 different families of monocotyledon plants, through inspection and identification of a range of commonly shared characteristics within that family.
  • Differentiate between at least 10 different families of dicotyledon plants which predominantly contain lower growing soft wooded plants or herbs; through inspection and identification of a range of commonly shared characteristics within that family.
  • Differentiate between at least 10 different families of dicotyledon plants which predominantly contain woody trees and shrubs; through inspection and identification of a range of commonly shared characteristics within that family.

Describing Plant Parts

When a botanist describes a new species, or when a gardener is accurately describing a plant to another gardener, there is a strict order in which he or she describes the components of the plant.  You start with those that are present for the longest time and finish with the most transient. The order is as follows:

  • Habit – e.g. woody or herbaceous; tree, shrub, or climber
  • Stems – e.g. round or square or ridged; hairy or hairless
  • Leaves – e.g. evergreen or deciduous, alternate or opposite, simple or compound
  • Flowers – e.g. in an inflorescence or solitary, type of inflorescence, number of sepals, colour of sepals, and so on!
  • Fruits – e.g. dry or fleshy
  • Seeds – e.g. smooth or rough, colour

Roots are rarely described and are rarely used in identification, but they can be useful. For example, the plants in the Berberis family (Berberidaceae) often have roots with a yellow inside.

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