Plant Taxonomy & Classification (HORT 2050) - Video Notes

Taxonomy: Definition and Purpose

  • Taxonomy: the science of identifying, naming and classifying plants
  • Distinguish plants by:
    • Morphology (structural form)
    • Anatomy (internal structure)
    • Physiology (plant functions)
    • Phylogeny (genetic relations)
    • Cytology (cell type)

History of Plant Taxonomy

  • Theophrastus: earliest record of categorizing plants by growth characteristics (trees, shrubs, half-shrubs, herbs)
  • Noted seed structure, germination, plant habitat range
  • Observed umbrella shape of flower clusters among parsley, fennel, and chervil

Scientific Classification of Plants

  • Taxonomy: science of identifying, naming and classifying plants
  • Distinguishing plants: how, based on careful study of:
    • Morphology
    • Anatomy
    • Physiology
    • Phylogeny
    • Cytology
  • Examples (illustrative): Lilyturf (Liriope muscari) and English lavender (Lavendula angustifolia)

Taxonomic Groups (Hierarchy)

  • Domain → Kingdom → Division → Class → Order → Family → Genus → Species
  • Kingdoms: Monera, Protista, Fungi, Animalia, Plantae

Plant Divisions

  • Nonvascular Plants: Liverworts, Hornworts, Mosses
  • Vascular Plants:
    • Seedless: Ferns, Club Mosses, Horsetails
    • Seeded: Pinophyta (Gymnosperms), Magnoliophyta (Angiosperms)

Gymnosperms

  • Nonflowering; seeds in cones
  • Leaf structure: narrow, needle-like; generally evergreen
  • Examples: Conifers, Cycads, Ginkgoes
  • Notable: Ginkgo biloba (a living fossil); Sago palm; Pinecone

Angiosperms

  • Flowering plants; seeds in a fruit
  • Leaves: broadleaf or grass-like; can be evergreen or deciduous
  • Examples: flowering annuals/perennials; fruits and vegetables; woody ornamentals

Angiosperms: Monocots vs Dicots

  • Monocotyledons (Monocots): grasses and grass-like plants
  • Dicotyledons (Dicots): broad-leaved plants

Plant Families

  • Contain similar morphological characteristics; used for identification
  • In the same family, flora often share:
    • Similar floral structures
    • Attract similar pests and diseases
    • Similar nutrient and growth requirements
  • Important families:
    • Rosaceae – Rose Family
    • Poaceae – Grass Family
    • Fabaceae – Legumes/Bean Family
    • Lamiaceae – Mint Family
    • Asteraceae – Aster Family

Kingdom, Division, Class, Order, Family, Genus, Species

  • Binomial system of nomenclature
  • Counts (illustrative group sizes):
    • Kingdom Plantae: ±280,000\pm 280{,}000 species
    • Phylum: ±250,000\pm 250{,}000 species
    • Class: ±235,000\pm 235{,}000 species
    • Order: ±18,000\pm 18{,}000 species
    • Family: ±3,500\pm 3{,}500 species
    • Genus: ±500\pm 500 species
    • Species: variable

Binomial Nomenclature

  • Definition: two-part name representing the species
  • Carl von Linné (Linnaeus): lived 17071707–17781778
  • Published Species Plantarum in 17531753; introduced binomial nomenclature
  • Genus name + specific epithet = scientific name
  • Rules:
    • Genus name capitalized; specific epithet lowercase
    • Italicize or underline the binomial name
    • Include the authority (person who named the plant) after the binomial name
  • Example: Magnolia grandiflora L.
  • Historical note: Linné organized plants into classes based on floral structure

Binomial Nomenclature: Examples and Details

  • Examples:
    • Magnolia grandiflora L.
    • Magnolia stellata
    • Magnolia virginiana
    • Magnolia macrophylla
    • Magnolia acuminata
  • Genus name + specific epithet = scientific name

Binomial Nomenclature: Varieties, Subspecies, and Cultivars

  • Variety (var.): recognized variations within a species; underlined/italicized
    • Example: Acer rubrum var. drummondii
    • Native range: Acer rubrum var. drummondii Swamp Red Maple
  • Cultivar: not underlined/italicized; enclosed in single quotes
    • Example: Acer rubrum 'Red Sunset' (Red Sunset Maple)

Latin in Plant Names: What Can It Tell Us?

  • Latin indicates geographic origin and wild habitat
    • Ostrya virginiana = American Hop Hornbeam ("of Virginia")
    • Fagus sylvatica = Common beech; Sylvatica/ woods origin
    • Taxus baccata 'fastigiata' = Irish yew; Fastigiate/erect habit
  • Additional clues:
    • Leaf shape, edge, size, texture, color
    • Flower shape, size, color and flowering time
    • Color of leaves/flowers/wood
    • Scent/aroma
    • Commemorative names (named after botanists, discoverers, etc.)
  • Examples: Acer palmatum (Japanese maple) – palm-shaped leaves; Liriodendron tulipifera (Tulip poplar)

Common Classification of Plants

  • Seasonal growth cycles: Annual vs perennial
  • Seasonal growth temperatures: Warm season vs cool season
  • Place of origin: Temperate, tropical, or subtropical
  • Edible organs: Root vegetables vs leafy greens

Learning Objectives (Review)

  • Define taxonomy and universal nomenclature
  • Understand scientific vs common classification methods
  • Summarize the history of plant classification
  • Recognize major taxonomic plant groups and key classifications in horticulture
  • Compare Angiosperms and Gymnosperms
  • Apply binomial nomenclature rules and write plant names correctly
  • Describe common classifications of plants
  • Define and identify plant varieties and cultivars
  • Refer to Chapter 2 for further reading

Quick Activity Prompts

  • What's your favorite plant? Look up its scientific name online and write it down
  • Search for a cultivar or variety of that plant; write full name including cultivar/variety