Uploaded January 2023 | Updated September 2026, 2 weeks ago
Plant Taxonomy and Nomenclature
Professor DeBacco
Nomenclatural Codes and Resources
International Codes that set the rules for plant nomenclature
These are authoritative but also technical which may not make them as easy to read as some would like.
The International Code of Nomenclature for Algae, Fungi, and Plants, Shenzhen Code, 2018.
International Association for Plant Taxonomy. Abbreviation: ICN
Serves the needs of science by setting precise rules for the application of scientific names to taxonomic groups of algae, fungi, and plants
iapt-taxon.org/nomen/main.php
The International Code of Nomenclature for Cultivated Plants, 9th Edition, 2016
International Association for Horticultural Science. Abbreviation: ICNCP
Serves the applied disciplines of horticulture, agriculture, and forestry by setting rules for the naming of cultivated plants
ishs.org/sites/default/files/static/ScriptaHorticulturae_18.pdf
Additional Resources
Plant Names: A guide to botanical nomenclature, 3 rd Edition, 2007. Spencer, R., R. Cross, P. Lumley. CABI Publishing.
..and..
The Code Decoded, 2nd Edition, 2019. Turland, N. Advanced Books.
ab.pensoft.net/book/38075/list/9
Parts of a Name
Genus Name- should be written in italics with first letter capitalized.
Example: Pinus
Specific Epithet- should be written in italics and in lower case.
Example: strobus
Species Name- comprised of the genus name followed by the specific epithet. It should be written in italics, with the first letter of the genus capitalized. A species name comprised of a genus name and specific epithet is also known as a binomial.
Example: Pinus strobus
Properly Naming PlantsCultivar vs Variety
Both appear as part of the scientific name of a plant and they always follow the genus/species name.
Cultivar = means a cultivated variety; thus, a cultivar is selected and cultivated by humans, most cultivars are developed by plant breeders and are called hybrids
Variety = a variation within a plant species that develops naturally in the environment. (Does not require human intervention.)
How To Distinguish a Cultivar from a VarietyHow was it Developed?
Varieties develop naturally.
Cultivars are developed through human intervention.
How To Distinguish a Cultivar from a VarietyWhat Characteristics Does it Have?
Seeds planted from a variety tend to grow true to type
Meaning, the offspring retains the parent plant's unique characteristics
Writing a Variety
When writing a variety name within a plant’s full scientific name, the species name comes first followed by the abbreviation "var." followed by the variety name all lowercase and italicized.
Ex. Rudbeckia hirta var. pulcherrima
Plant Variety and Breeders’ Rights
A plant variety is a legal term coined by the International Union for the Protection of New Varieties of Plants (UPOV) that recognizes certain cultivars as official plant varieties in order to grant the creator of the cultivar legal protection.
This has a different meaning than variety on its own.
This practice is commonly referred to as plant breeders' rights.
The term “plant variety” describes a legally protected cultivar and should not be confused with the taxonomic rank term of variety.
When writing the complete scientific name of a plant cultivar, the cultivar name comes after the name of the genus and species.
The cultivar name is unitalicized, set off in single quotation marks, and the first letter of each word is capitalized.
Ex. Rudbeckia hirta ‘Denver Daisy’.
Establishing a New Cultivar
To create a new cultivar, growers crossbreed parent plants that each have desirable characteristics in the hopes that their offspring will inherit those traits.
Plant Hybrids
When two different cultivars undergo cross-pollination, the seed that those two plants produce grows a hybrid plant.
Natural Plant Hybrids
When two different plant species grow near each other, the wind or a pollinating insect can cross-pollinate the plants.
This produces a hybrid seed that falls onto the ground and grows into a new hybrid plant.
Human Generated Plant Hybrids
Human plant breeders create most hybrid plants in order to grow a plant with positive traits from both parent plants.
Even though hybrid seeds can be made randomly in nature, hybrid seeds that you purchase are deliberately produced by humans.
Properly Naming PlantsStrain
Strains are often seen as inherently artificial concepts, characterized by a specific intent for genetic isolation.
This is most easily observed in microbiology
(Bacterial) Strains are derived from a single cell colony and are typically limited by the physical constraints of a Petri dish.
Strains are also commonly referred to within virology, botany, and with rodents used in experimental studies.
It is not advised to apply this name for plants.
Link to Lecture Slides:
*Due to the description character limit the full work cited for "Plant Taxonomy and Nomenclature" can be viewed at...
Plant Taxonomy and Nomenclature
Professor DeBacco
Nomenclatural Codes and Resources
International Codes that set the rules for plant nomenclature
These are authoritative but also technical which may not make them as easy to read as some would like.
The International Code of Nomenclature for Algae, Fungi, and Plants, Shenzhen Code, 2018.
International Association for Plant Taxonomy. Abbreviation: ICN
Serves the needs of science by setting precise rules for the application of scientific names to taxonomic groups of algae, fungi, and plants
iapt-taxon.org/nomen/main.php
The International Code of Nomenclature for Cultivated Plants, 9th Edition, 2016
International Association for Horticultural Science. Abbreviation: ICNCP
Serves the applied disciplines of horticulture, agriculture, and forestry by setting rules for the naming of cultivated plants
ishs.org/sites/default/files/static/ScriptaHorticulturae_18.pdf
Additional Resources
Plant Names: A guide to botanical nomenclature, 3 rd Edition, 2007. Spencer, R., R. Cross, P. Lumley. CABI Publishing.
..and..
The Code Decoded, 2nd Edition, 2019. Turland, N. Advanced Books.
ab.pensoft.net/book/38075/list/9
Parts of a Name
Genus Name- should be written in italics with first letter capitalized.
Example: Pinus
Specific Epithet- should be written in italics and in lower case.
Example: strobus
Species Name- comprised of the genus name followed by the specific epithet. It should be written in italics, with the first letter of the genus capitalized. A species name comprised of a genus name and specific epithet is also known as a binomial.
Example: Pinus strobus
Properly Naming PlantsCultivar vs Variety
Both appear as part of the scientific name of a plant and they always follow the genus/species name.
Cultivar = means a cultivated variety; thus, a cultivar is selected and cultivated by humans, most cultivars are developed by plant breeders and are called hybrids
Variety = a variation within a plant species that develops naturally in the environment. (Does not require human intervention.)
How To Distinguish a Cultivar from a VarietyHow was it Developed?
Varieties develop naturally.
Cultivars are developed through human intervention.
How To Distinguish a Cultivar from a VarietyWhat Characteristics Does it Have?
Seeds planted from a variety tend to grow true to type
Meaning, the offspring retains the parent plant's unique characteristics
Writing a Variety
When writing a variety name within a plant’s full scientific name, the species name comes first followed by the abbreviation "var." followed by the variety name all lowercase and italicized.
Ex. Rudbeckia hirta var. pulcherrima
Plant Variety and Breeders’ Rights
A plant variety is a legal term coined by the International Union for the Protection of New Varieties of Plants (UPOV) that recognizes certain cultivars as official plant varieties in order to grant the creator of the cultivar legal protection.
This has a different meaning than variety on its own.
This practice is commonly referred to as plant breeders' rights.
The term “plant variety” describes a legally protected cultivar and should not be confused with the taxonomic rank term of variety.
When writing the complete scientific name of a plant cultivar, the cultivar name comes after the name of the genus and species.
The cultivar name is unitalicized, set off in single quotation marks, and the first letter of each word is capitalized.
Ex. Rudbeckia hirta ‘Denver Daisy’.
Establishing a New Cultivar
To create a new cultivar, growers crossbreed parent plants that each have desirable characteristics in the hopes that their offspring will inherit those traits.
Plant Hybrids
When two different cultivars undergo cross-pollination, the seed that those two plants produce grows a hybrid plant.
Natural Plant Hybrids
When two different plant species grow near each other, the wind or a pollinating insect can cross-pollinate the plants.
This produces a hybrid seed that falls onto the ground and grows into a new hybrid plant.
Human Generated Plant Hybrids
Human plant breeders create most hybrid plants in order to grow a plant with positive traits from both parent plants.
Even though hybrid seeds can be made randomly in nature, hybrid seeds that you purchase are deliberately produced by humans.
Properly Naming PlantsStrain
Strains are often seen as inherently artificial concepts, characterized by a specific intent for genetic isolation.
This is most easily observed in microbiology
(Bacterial) Strains are derived from a single cell colony and are typically limited by the physical constraints of a Petri dish.
Strains are also commonly referred to within virology, botany, and with rodents used in experimental studies.
It is not advised to apply this name for plants.
Link to Lecture Slides:
*Due to the description character limit the full work cited for "Plant Taxonomy and Nomenclature" can be viewed at...
