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EC1272 Classification and Naming of

Anne M. Streich, Associate Professor of Practice Kim A. Todd, Extension Landscape Specialist

Extension is a of the Institute of Agriculture and Natural Resources at the University of Nebraska–Lincoln cooperating with the Counties and the United States Department of Agriculture. University of Nebraska–Lincoln Extension educational programs abide with the nondiscrimination policies of the University of Nebraska–Lincoln and the United States Department of Agriculture. © 2014, The Board of Regents of the University of Nebraska on behalf of the University of Nebraska–Lincoln Extension. All rights reserved.

Classification and Naming of Plants

Anne M. Streich, Associate Professor of Practice Kim A. Todd, Extension Landscape Specialist

Classifying based on similarities helps provide to the thousands of living organisms on earth. By understanding the classifica- tion system, gardeners and profes- sional landscape managers can make appropriate decisions for propagat- ing, controlling, or managing land- scape plants. Properly naming plants through careful classification allows professionals and gardeners to eas- a b ily communicate with each other and with others across the world without Figure 1. Common names are frequently used when talking about plants. being confused by common names Unfortunately, confusion occurs when multiple common names are used (Figure 1). for the same or a is used for more than one plant. is a common example. Most people think of the well-known Classification of Plants annual ( X hortum) that often has large clusters of red, pink or white flowers as geranium (a). But Geranium is also the for a lesser-known perennial which has smaller, single flowers in shades of is the science of iden- pink and purple and different foliage characteristics (b). Using scientific tifying, classifying, and naming organ- names eliminates the potential confusion that occurs when communicat- isms. In 1735, created a ing about plants. hierarchical classification system that places all organisms into successively smaller groups that assume organisms and specific epithet, which together continues to evolve. Plants are occa- within a specific group resemble one define the . Before the binomial sionally moved from one classifica- another more than organisms within system was adopted, plants could have tion to another or names are slightly a different group. His system classified very long scientific names that could changed to reflect new knowledge. plants based on sexual reproductive be easily changed. With the binomial These changes can be observed in text- parts. Other plant classification systems system, there can be several common books. used different morphological charac- names for a single plant, but there is teristics, such as and stem qualities, only one official scientific name. to classify plants. Linnaeus’ basic clas- The scientific binomial naming system Kingdoms sification method is still used today. The is governed by the International Code classification system groups, in order of . from largest to smallest, are , Kingdom is the broadest divi- or division, , order, , is an emerging sci- sion of organisms. Linnaeus originally genus, and species (Figure 2). ence that uses today’s technology to divided all organisms into two king- classify plants based on evolutionary doms — the Plant Kingdom and the Linnaeus also described a bino- relationships that can be identified Kingdom. With new knowl- mial naming system. All organisms through molecular sciences. With edge and discovery, this classification were given two names — the genus new technology, plant classification system was expanded to five kingdoms

© The Board of Regents of the University of Nebraska. All rights reserved. 3 in the 1900s, and more recently into six kingdoms. Organisms are differen- tiated into kingdoms based on various characteristics including the number Species ~ 300,00 of cells (one to multicellular), cell (complex or simple), presence or absence of cell walls and/or organelles, Genus ~ 16,167 and the ability to make their own food. The six kingdoms recognized today are described below. Family ~ 620 • Plant Kingdom. Plants are mul- ticellular, have complex cell walls, are primarily immotile, and make Order their own food. Organisms that make their own food are called au- totrophs. More information about the processes plants use to create Class food can be found in EC1268, Plant Growth Processes: Transpira- tion, , and Respira- tion. Without plants, on earth Division would not exist. and other heterotrophs (organisms

that cannot use atmospheric CO2 to create complex organic mole- Plant Kingdom cules) rely on plants for their food. The plant kingdom is the second Figure 2. Plant kingdom contains all the known plants, approximately largest kingdom and contains 300,000 plant species. As plants are classified into divisions, classes, an estimated 300,000 plant spe- orders, families, and genera more specific groupings of plants are cies. Within the plant kingdom, found until each plant is specifically named. plants are further categorized into non-vascular and vascular plants. Non-vascular plants do not con- tain water-conducting tissues or landscapes are beneficial because considered delicacies. For more true , , or stems. Plants of their or preda- detailed information about plant with non-vascular systems include tory activities. For more detailed diseases, see EC1273, Introduction and liverworts. Vascular information about classifi- to Plant Diseases. plant systems contain water and cation see EC1588, Introduction to nutrient conducting tissues called Entomology. EC1260, Landscape • Protista Kingdom. Most Protista and . Vascular plants Diagnostic Guide for Problems are unicellular, complex cells that have true roots, stems, and leaves Affecting Woody Ornamentals and acquire nutrients through pho- (Figure 3). Herbaceous Perennials provides tosynthesis or by eating other information on signs and symp- organisms. This kingdom includes • Animal Kingdom. are toms of common pests a of microscopic organ- multicellular, consist of complex in home landscapes. isms that vary quite a bit from one cells, and rely on plants for their another, unlike organisms in the food. The animal kingdom is the • Fungi Kingdom. Fungi are pri- other five kingdoms. Slime molds largest kingdom. It has more than marily multicellular, complex and are in the Protista king- a million species, with more than cells, but they do not make their dom. three-fourths of all species being own food. They usually obtain (primarily ). In food from decaying organisms. • Eubacteria Kingdom. Eubacteria landscapes, wildlife and insects Fungi are often the causal agent are complex, unicellular organ- are the primary animals of inter- of many plant diseases. However, isms. Most are in this est, and many insects found in many fungi, including morels, are kingdom. Bacteria have various

4 © The Board of Regents of the University of Nebraska. All rights reserved. Plant Kingdom b

Non-vascular Plants Vascular Plants No , stem Structures look Producer Producer or leaf-like like root, stem, structures or leaf No Flowers Algae Angiosperms One Seed Leaf Two Seed Leaves Monocot Dicot

Figure 3. All members of the plant kingdom can be classified based on their morphological differences. Some biologists classify algae in the Protista kingdom, while other plant biologists would classify them as the sim- plest member of the plant kingdom.

, hybrid, and authority nota- or functions, including being causal tions. (Figure 4). agents for some plant diseases, biological control agents for some • Plant Division. Plant divisions ■ Monocotyledons (monocots) pests, nitrogen fixers in some classify plants based on whether include grasses, , lilies, or- plant species (), and serv- they reproduce by or . chids, and . Distinguish- ing as the primary organic matter Spore-bearing plants include ing characteristics include one decomposers in the soil. Bacteria ferns, club mosses, and horsetail. seed leaf, a vascular system in can live in environments that have Seed-bearing plants are divided paired bundles throughout the (aerobic) or lack (anaerobic) oxy- into gymnosperms and angio- stem, floral parts in multiples gen for respiration. sperms. of three, and parallel leaf veins. Meristematic regions, of • Kingdom. Archaea are ■ Gymnosperms are non- plant growth, are low in the unicellular organisms found in flowering plants that produce plant until vegetative growth extreme environments, such as naked seeds. , , changes to reproductive very hot springs or highly acidic and , such as growth. or alkaline waters. Archaea is and , are examples of the last kingdom discovered and gymnosperms. There are 700 ■ Dicotyledons (dicots) have new knowledge about where estimated species distinguishing characteristics these organisms live is still being in existence today. including two seed leaves, discovered. vascular systems arranged in ■ Angiosperms are flowering continuous rings around the plants that have their seeds inside of the stem, floral parts Plant Classification and enclosed in a . There are in multiples of four or five, Naming 250,000 estimated angiosperm and netted leaf venation. Plant species in existence today. growth occurs from meristem regions above the ground. All kingdoms are divided into • Plant Class. The two plant classes divisions , which are then further under the angiosperm division are • Plant Order. Plant order is not divided into classes, orders, families, valuable classification tools due to commonly used as a way to dis- genera, and species. Each species rep- differences in their growth char- tinguish plants for gardeners, but resents a specific plant. Plants can be acteristics. Angiosperm plants are is used to group similar families further described by using variety, placed into one of two classes — when learning or teaching about

© The Board of Regents of the University of Nebraska. All rights reserved. 5 First leaf

Meristem or growing point

Two

a b

First leaf

Meristem or growing point

Two cotyledons Newest leaf First and oldest leaf

Meristem or growing point

Figure 4. One of the key differences in dicot growth versus monocot growth is the location of the growing point or meristems. In dicots, the first true leaves emerge above the cotyledons and the plant’s meristems continue to grow aboveground (a). Monocots grow from meristems low in the plant, near the soil surface, until the plant moves from vegetative growth to reproductive (flowering) growth. Understanding where the growing point is located is important for making management decisions, such as where to prune and how low to mow.

Newest leaf

First and oldest leaf

Meristem or growing point

Figure 5. Plants are grouped into families because of similar morphological characteristics. Even with vastly different visual appearances, the presence of legumes on plants easily places them into family; blue false indigo has round legumes; Kentucky coffeetree has thick, leathery legumes; and Illinois bundleflower has ball-like clusters of small, wavy legumes.

6 © The Board of Regents of the University of Nebraska. All rights reserved. plants. Most plant order names a genus name preceding it. ■ . Cultivar desig- end in “-ales,” such as The specific epithet is always nates a cultivated variety. Bo- which has 24 families. written in lowercase, even if tanical varieties are naturally the name is a proper noun occurring; cultivars are pur- • Plant Family. Plants in the same commemorating a person or posely bred and propagated. family have similar flower, fruit, place that would normally be Although some cultivars can and seed structures. Most families capitalized, and is either un- be propagated by seed, asexual in the plant kingdom are angio- derlined or italicized. (divisions, graft- sperms. The family name is often ing, culture) should be the first level of plant classification ■ Species. Species is the name of used with cultivars to ensure discussed when talking about spe- a specific plant. The genus and offspring that are true to type. cific plants, as pest problems and specific epithet are combined For cultivars of annual plants management practices within a to name the species. When (such as tomatoes, marigolds, family may be similar. The three related species in a particular and ), sexual repro- largest plant families are Astera- genus are listed, they can be duction is controlled so that ceae (sunflower family), Orchida- written as cordata, T. the desired seed is produced. ceae (orchid family), and Fabaceae americana, and T. tomentosa, Cultivars are always capital- ( family) with an estimated with the genus spelled out for ized and indicated by putting a 24,000, 20,000, and 18,000 plants only the first item in the list. single quotation mark around within each. Family names always If the species is unknown, the the name or by abbreviating it end in “-aceae” (Figure 5). plant can be written as Tilia sp. as cv. Both of the following are or Tilia spp. for multiple spe- correct designations of a culti- Genus. Plants within a family ■ cies. var: Acer platanoides ‘Crimson that have more characteristics King’ or Acer platanoides cv. in common with one another Some plants are further distin- Crimson King (Figure 6). than other plants of the same guished through the use of variety, cul- family are placed in a genus. tivar, hybrid, or authority designations. ■ Hybrids. Hybrids are typically The genus name is the first These items are added after the specific crosses between two varieties, part of the scientific or Latin epithet. species, or two distinct parent name for a specific plant. The lines. A hybrid is identified by ■ Variety. Variety is used to sub- first letter of the genus name placing an “×” before the spe- divide a species and is written is always capitalized and the cific epithet, as in as the third name in a species word is always italicized or ×burkwoodii. Viburnum × designation. Varieties are natu- underlined, as in Quercus or burkwoodii can also be written rally occurring variations that Quercus. Quercus is the as Viburnum carlesii × Vibur- have inheritable differences genus. There are thousands of num utile to show parentage. from the straight species. For genera (plural of genus) in the The “×” is not italicized. plant kingdom. example, triacan- thos, common honeylocust, ■ Authority. The authority is ■ Specific epithet. Specific epi- contains branched thorns and used in some references to thet is the second part of the is not used very often in the indicate the first person who scientific name. The specific landscape industry. Conversely, described the species. The epithet may describe a plant Gleditsia triacanthos var. iner- authority follows the species characteristic, the location mis, a thornless honeylocust, name and is usually abbrevi- where it was found, or the is used quite often. Subspe- ated, such as Quercus rubra person who discovered it. For cies (ssp.) is sometimes used L. The “L.” stands for Carl exam ple, repens means creep- instead of variety, but the dis- Linnaeus . ing and is the specific epithet tinction between these terms for many plants that have a is not always clear. Knowing how to classify and name creeping growth . The may be used when a plant is plants in a landscape is important specific epithet may be used geographically isolated. Variet- for successful plant management and with any number of differ- ies should either be underlined placement in landscapes. Some plants ent genera names, as in Tilia or italicized. The abbreviation are known for quick growth and weak americana or ameri- var. is not italicized or under- (Populus genus), high poten- cana. It is never used without lined. tial for diseases (Rosaceae family),

© The Board of Regents of the University of Nebraska. All rights reserved. 7 preferred growing conditions (Salix in moist conditions), or brilliant fall First letter capitalized color (Acer genus). Knowing the name Family Name NOT italicized of specific plants will help gardeners and landscape managers identify those First letter capitalized general characteristics and become Italicized better managers of the landscape. Genus

All letters lowercase fulgida Italicized Summary Specifc Epithet

GenusGenus + Speci + Specificfc Epithet Epithet = Species = Species All organisms are classified into one of six kingdoms. The plant king- All letters lowercase dom, the second largest kingdom, var. sullivantii var. NOT italicized contains an estimated 300,000 species. Variety Other letters italicized Most of the plant species found in managed landscapes are classified as ‘Goldsturm’ First letter capitalized angiosperms or plants that have true Cultivar NOT italicized flowers. Naming of plants is done in In single quotes a systematic method to allow profes- sionals and gardeners to easily com- Rudbeckia fulgida var. sullivantii ‘Goldsturm’ municate with each other and with Common Name: Goldsturm rudbeckia others across the world without being confused by common names.

Additional information

Detailed information about plant classification can be found at the two websites listed below.

The Plant List, http://www.theplantlist. org.

USDA Plants, http://plants.usda.gov.

Figure 6. Landscape management and design often focus on classifying plants from the family level down to the specific plant name. Effective communication relies on following the proper writing format for plant names.

This publication has been peer reviewed.

UNL Extension publications are available on- line at http://extension.unl.edu/publications.

8 © The Board of Regents of the University of Nebraska. All rights reserved.