Lecture 7: Plant Identification

Introduction to Taxonomy

  • Taxonomy: The science and practice of classifying and naming living organisms.

  • Importance for horticulture: Taxonomy is used differently in horticulture compared to pure botany; the emphasis is on practical identification rather than broader scientific classification.

  • Learning outcome focus: Student Learning Outcome 3.5 - Utilize effective plant identification and botanical terminology.

Key Concepts

What is Taxonomy?

  • Taxonomy involves labeling and organizing living organisms into categories, aiding in systematic study.

What is Botanical Nomenclature?

  • The formal science of naming plants, following conventions for clarity and consistency.

What is Binomial Nomenclature?

  • A two-name system of classification developed by Carl Linnaeus in the 18th century.

  • Structure: Genus name and specific epithet.

  • Example: Trachelospermum jasminoides (commonly referred to as star jasmine).

Importance of Scientific Names

  • Common names can be misleading or confusing due to regional variations; for example, "star jasmine" may refer to different species.

  • Scientific names provide a universal language, enabling clear and unambiguous communication among professionals globally.

Taxonomical Hierarchy

  • Hierarchy Levels:

    1. Kingdom

    2. Division (or Phylum)

    3. Class

    4. Order

    5. Family

    6. Genus

    7. Specific Epithet

  • Example of Taxonomical Classification (Plant Kingdom):

    • Kingdom: Plantae (multicellular autotrophic organisms).

    • Major groups:

    • Angiosperms (flowering plants) - seeds contained in fruit.

    • Gymnosperms (naked seeds, e.g., conifers).

    • Vascular plants without seeds - e.g., ferns (Pterophyta) and mosses (Bryophyta).

Unique Characteristics of Groups

  • Angiosperms:

    • Largest and most diverse group.

    • Seed encased within ovule vessel (fruit).

  • Gymnosperms:

    • Seeds exposed (naked) after conifer cones mature.

Importance of Family Names in Horticulture

  • Knowledge of plant families aids in understanding plant characteristics, diseases, and care.

  • Example: Plant families often end in '-aceae'. For example,

    • Rosaceae (rose family) includes roses, apples, and strawberries.

    • Asteraceae (aster family) relates to composite flowers like daisies.

Specific Epithet and Common Names

  • Common Names:

    • Ambiguous and vary by region (e.g., "marigold" can refer to different species such as Tagetes or Calendula).

  • Genus and Specific Epithet: Essential for precise identification (e.g., Acer rubrum for red maple).

  • Species: Refers to both genus and specific epithet.

Subspecies and Variety

  • Subspecies:

    • Indicates natural geographical variation within a species.

    • Identified in nature based on habitat differences (e.g., Eucalyptus minifera subspecies maculosa).

  • Variety (Var):

    • Indicates variations found in nature across different regions without geographic isolation.

  • Form (f.):

    • Specified minor deviations within a variety, often distinguished by different leaf shapes or growth habits (e.g., Viburnum placatum and Viburnum placatum form tomatosum).

Cultivar

  • A cultivated variety, often modified or maintained by humans, which does not exist in nature.

  • Denoted by single quote marks around the cultivar name (e.g., Acer rubrum 'October Glory').

Hybrids

  • Result from cross-pollination of two species within the same genus (e.g., Acer rubrum x Acer saccharinum = Acer freemanii).

  • Hybrids can also form between different genera (e.g., Chitalpa, a cross between Catalpa and Chilopsis).

Writing Botanical Names

  • Formatting Rules:

    • Genus name: capitalized and italicized.

    • Specific epithet: lowercase and italicized.

    • Cultivar names: capitalized, in single quotes, and not italicized.

    • Common names: capitalized, not italicized.

  • Example of formatting: Quercus rubra (red oak), Acer rubrum 'October Glory'.

Sources of Botanical Names

  • Influenced by historical languages (Latin, Greek, Hebrew, Arabic) and contemporary usage from various cultures.

  • Names may be based on characteristics, geographical locations, or homage to individuals who discovered or developed the plant.

Conclusion

  • Understanding the language of botanical nomenclature is essential for effective communication in horticulture.

  • Recognize practical implications of scientific names in landscaping, plant selection, and horticultural practices.

Closing Remarks

  • Students encouraged to reach out for further discussion or clarification regarding plant identification and terminology.