Plant Taxonomy

Variety of plant groups in Banff National Park, Alberta (Don White, iStockphotos)

Variety of plant groups in Banff National Park, Alberta (Don White, iStockphotos)
How does this align with my curriculum?
Learn about the categories, or phylum, of the plant kingdom with examples from each.
Scientists like to classify living things in order to better understand their relationships. One way to do this is using Taxonomy. Taxonomy is the science of naming, describing and classifying organisms.
Modern taxonomy began in the mid-1700s. This is when Carl Linnaeus established a system to classify living organisms. He did this by giving every species a two-part Latin-based name. This is also known as a scientific name.
The Evolution of Classification Systems
Linnaeus classified organisms that could be seen with the naked eye into two large groups known as kingdoms. There were two kingdoms. The animal kingdom and the plant kingdom. This was based on whether or not they could move. Fungi were included with plants. Linnaeus further divided organisms by shared physical characteristics. His sub-groups included classes, orders, genera, and species. With the invention of the microscope around 1590, new organisms were discovered. This led to the need for more kingdoms.
The Five Kingdom system was first proposed in 1969. In this system, prokaryotes were put into a single kingdom called Monera. Most multicellular eukaryotes were either in the kingdom plantae (plants), animalia (animals) or fungi. Eukaryotes that did not fit elsewhere were put in the kingdom protista.
Not long after the five kingdom system was created, Carl Woese proposed a Six Kingdom system. He split the monera kingdom into two new kingdoms. These were archaea, which were ancient single-celled organisms and bacteria.
But Carl wasn’t finished thinking about classification. In 1990, he developed what is known as the Three Domain system. This system groups organisms mainly based on differences in the structure of the ribonucleic acid (RNA) found in their ribosomes. Within the three domains there are six kingdoms. These domains closely mirror the ones from 1977.

Three different ways of organizing the kingdoms of life (©2022 Let’s Talk Science).
Image - Text Version
Shown is a colour illustration of the evolution of the kingdom classification system from the earliest in 1969 to 1977 and 1990. Colourful blocks shown from left to to right, display the names of each kingdom .
1969: Five kingdom System
1977: Six Kingdom System
1990: Under three domains named bacteria, archaea and eukarya. Bacteria is further divided into the kingdom eubacteria, archae-bacteria is classified under the domain of archaea, and protist, plantae, fungi and animalia are all grouped under eukarya.
The Kingdom Plantae
All members of the plant kingdom share common features.
Plants:
- are made of more than one cell. We call them multicellular
- have cell walls
- mainly cannot move
- make their own food
The plant kingdom can be divided into groups based on plant structures. Plants with similar structures are grouped together. In the plant kingdom, these groups are called divisions.
Did you know?
The term “division” is used for plants and the term “phylum” is used for animals. Some scientists use the word “phylum” for both.
Plant Divisions
Plants can first be divided into two groups. These are plants that make seeds and plants that do not make seeds. We call the subdivision of plants that make seeds phanerogams. We call the subdivision that does not make seeds cryptogams.

Plant divisions with examples (©2022 Let’s Talk Science).
Image - Text Version
Shown is a colour flowchart of divisions within the plant kingdom with examples from each.
Starting from the top, green blocks with text have connecting lines that branch out to other related blocks below. Under each block is an colour image example of each plant division.
At top centre is Kingdom Plantae branching into two categories of has no seeds or has seeds. If no seeds, then the plants can then be further classified into has no true roots, stems or leaves, has some root and leaf-like structures or has roots, stems and leaves. If has seeds, the plant can be classified into the categories of has flowers or has no flowers.
The example of a plant with no true roots, stems or leaves is algae. A green plant with wavy looking narrow leaves is shown. Below the image is the word "Algae" and the group name "Chlorophyta".
The example of a plant that has some root and leaf-like structures or has roots are mosses and liverworts. A small green plant resembling tiny pipe cleaners is shown. Below the image are the words "Mosses and Liverworts" and the group name "Bryophyta".
The example of a plant that has roots, stems and leaves are ferns and horsetails. A green plant with feather-like leaves is shown. Below the image are the words "Ferns and Horsetails" and the group name "Pteridophyta".
There are two examples of plants that has no flowers or gymnosperms. The first are conifers, they have needle -like leaves. Below the image is the word "Conifers" and the group name "Pinophyta". The second example are ginkos and cycads, and they have wide green leaves. Below the image are the words "Ginkos and Cycads" and the group names "Ginkgophyta" and "Cycadphyta".
The example of a plant that has flowers are angiosperms. A plant with green, jagged narrow leaves and yellow round flowers is shown. Below the image is the word "Angiosperms" and the group name "Magnoliophyta".
From there, the subdivisions can be further divided. A common way to group cryptograms is by structure. Some cryptograms have roots, stems and leaves. Others only have some of these parts. Others still do not have any of these parts. Let’s look at these divisions in more depth.
Learn More
Who was Linnaeus?
Stories and videos about the life and work of Carl Linnaeus from The Linnean Society.
Taxonomy: Life's Filing System (2012)
Video (12:15 min.) from Crash Course explaining the history and importance of taxonomy.
What's in a Lichen? How Scientists Got It Wrong for 150 Years
Video (4:12 min.) from National Geographic. For 150 years, scientists believed lichen were defined by a symbiotic relationship between a fungus and algae. Meet the team of researchers who question this belief.
Algae Biofuel: Can Pond Scum Power The Planet?
A STEM in Context article by Let’s Talk Science. Learn about the potential of algae as a material for making biofuel.
What Gingko Leaves Can Tell Us About Climate Change
This video (3:56) from PBS/NOVA discusses how the gingko tree can be used as way to track the progress of atmospheric CO2 levels over history.
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