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					Plant Classification

Objectives of today‟s lecture:
• learn some common terms used to group
  plants
• learn the scientific protocols used to name
  plants so they can be universally
  recognized
• learn about the terminology used to
  distinguish plants within a species
Categorizing plants is an
ancient practice

• The Greek philosopher Theophrastus
  (~300 B.C.E.) published the first
  horticulture text book “Historia Plantarum”.
  In this text, plants are grouped together
  based on life span, growth habit, retention
  of leaves, and other traits
• Many of these characteristics are still used
  to classify plants
Categorizing plants

• Thousands of plants are used today in
  various areas of horticulture
• Convenient to group plants together
  based on common characteristics
   • life cycle
   • growth habit
   • environmental adaptation
   • end use or function
 Classification based
 on life cycle
• Annuals
  • plants that complete their life cycle (from
    seed to seed) in 1 year, e.g. petunia, peas
  Classification based
  on life cycle
• Biennials
  • plants that require all or part of two growing
    seasons; vegetative growth in the first year,
    followed by overwintering (low temperature);
    biennials flower in the second growing
    season, e.g. hollyhocks, carrot
 Classification based
 on life cycle
• Perennials
  • plants that persist for more than two seasons
    and do not die after flowering, e.g. maple,
    forsythia, tulips, daylily
 Classification based
 on life cycle
• Note that many biennials and perennials
  are grown as annuals
   • root crops such as carrots and beets
     are grown and harvested in one season,
     before they flower
   • tomatoes and poinsettias are grown in
     the US as annuals, but in S. America
     they grow as perennials
Classification based on
growth habit
Normally applied to perennial plants
• Woody plants
  • have persistent vegetative structures, e.g.
    trees and shrubs
Classification based on
growth habit
Herbaceous perennials
  • do not have woody structures and
    vegetation does not persist, e.g. daylily,
    hosta
 Classification based on growth
 habit

• Vines
  • climbing or trailing
    plants that require
    support, e.g.
    grapes, wisteria,
    clematis
 Classification based on growth
 habit

• Deciduous plants
  • shed leaves for part of the year
• Evergreens
  • never without leaves
  • they still shed leaves or needles after new
    organs are formed
 Classification based on
 environmental adaptation

• Temperature
  • Hardy, tolerant of low temperatures
  • Tender, unable to survive low
    temperatures
  • Warm season crops, e.g. corn, beans,
    melon
  • Cool season crops, e.g. lettuce, peas,
    broccoli
 Classification based on
 environmental adaptation

• Temperature
  • USDA hardiness zone map
  Classification based on
  environmental adaptation

• Requirement for water
  • Aquatic plants, which live in water
  • Xerophytes, which require very little water
• Soil conditions
  • Halophytes are adapted to salty conditions
  • Acidophytes require acid soils, e.g.
    rhododendrons
  • Metallophytes require high levels of specific
    metals
Classification based
on usage
• Edible plants
  • fruits (dessert or snack)
  • vegetables (savory)

  • Note that this classification differs from
    the botanical definition of a fruit. The
    strict botanical definition of a fruit is a
    structure that develops from the ovary
    in a flower. Using this definition, a
    tomato is a fruit while a strawberry is
    not.
  Classification based
  on usage

• Other culinary uses include:
  •   nuts (hard seeded fruits)
  •   herbs (fresh or dried vegetative tissue)
  •   spices (dried fruit or bark)
  •   beverages (tea and coffee)
• Medicinal plants
  • source of pharmaceuticals, e.g. digitalis from
    foxglove, taxol from a yew
Classification based
on usage
• Industrial plants
  • provide raw materials for industrial
    use
    • oils from oil palm or jojoba
    • fibers from flax or hemp
Classification based
on usage
• Ornamental uses
  • nursery crops, e.g. trees and shrubs
  • ground covers, e.g. ivy and pachysandra
  • bedding plants, e.g. petunias and pansies
  • foliage plants, for indoor decoration
  • pot crops, e.g. poinsettia and
    chrysanthemum
  • floriculture crops, e.g. roses and
    carnations
  Limitations of these
  classification systems

• Classifications are very subjective
  • Based on your perspective, a hazel shrub can
    be regarded as a source of nuts, an
    ornamental landscape shrub, or a weed.
  • What is grown as an annual in one region is
    classified as a perennial elsewhere.
  • Plants that are considered hardy in Florida or
    Georgia are considered tender in Indiana.
Limitations of these
classification systems

• These classifications are not understood
  throughout the world, in different
  languages or across cultures
• Common names can be confusing
  • Same name used to describe different plants
  • Different names to describe the same plant
Scientific classification
system

Advantages of this system include:
• common universal designation
• based on international convention
• uses Latin, a “dead” language that will not
  change

All organisms are divided into a series
  of categories called “taxa”
 Scientific classification system
Kingdom (plant, animal, bacteria, etc.)
  Division
   Class
      Order
        Family
          Genus
           Species


• Members of each successive category are more
  similar to each other
 Scientific classification system

• Developed by Carl von
  Linne, a Swedish
  physician. He is better
  known as Linnaeus,
  the father of taxonomy
• In 1753, “Species
  Plantarum” was
  published , which
  described his new
  classification system
 Scientific classification system

• Linnaeus‟ system of classification is based
  on stable morphological features, especially
  flowers
• Avoids features that can vary with age of the
  plant or the environment in which the plant is
  grown
• Incorporates the concept of evolution, i.e.
  plants with similar features share a common
  ancestor
The Binomial System

Each name has two components:
  Genus + specific epithet = species
Prunus persica (peach)
• belongs to the Genus Prunus
• species name is Prunus persica

Conventions that apply to this system:
  • written in italics (or underlined)
  • first letter of the Genus is capitalized
The Binomial System

Genus - a group of similar organisms, some
 of which may interbreed
Species - members will interbreed and
 produce similar progeny
No matter your origin or situation, Solanum
 tuberosum is recognized as referring to
 pomme de terre, kartoffel, potato
The Binomial System

• Avoids confusion that can arise when
  using common names




    Rose of Sharon         Rose of Sharon
  Hypericum calycinum     Hibiscus syriacus
 Additional terms used with
 the binomial

Prunus persica (L.) Batsch
  • (L.) indicates the “authority”, the individual
    who first named this species
  • Linnaeus is indicated by (L.)
  • Others are written out in full
  • Amendments to the classification are added
    after the authority, e.g. Batsch
  Additional terms used with
  the binomial
• Botanical varieties
  Juniperus communis var. depressa
     • Indicates a botanical variety within this species of
       juniper, in this case plants with a distinctive low-
       growing (depressed) habit
  Additional terms used with
  the binomial
• Interspecific hybrids
  Forsythia X intermedia
     • “X” indicates these plants result from a cross
       between two different species (F.suspensa and F.
       viridissima) in the genus Forsythia
Additional terms used with
the binomial

Prunus persica cv. Redhaven
• cv. Redhaven indicates a cultivar
Also written as Prunus persica „Redhaven‟
• single quotation marks indicates the cultivar
• Cultivars are cultivated varieties
• Cultivars are groups of plants within a
  species that share common characteristics
  and maintain their identity
Summary

• Many different methods used to classify
  plants used in horticulture
• The scientific binomial system provides a
  universal protocol that does not depend
  on variable factors

				
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