Decoding Botany: Making Sense of Plant Classification
By Ryan Dorn, SouthernSeeds.com
As you step outside into the natural world, it’s easy to be captivated by the verdant array of plants that make up our gardens, parks, and wilderness areas. From the delicate blossoms of spring to the sturdy oaks that seem to weather every season, there’s an intricate and fascinating system that organizes all these plant species. It’s like a vast, interconnected family tree extending its branches across the globe and throughout time. This system, known as plant taxonomy, may seem a bit complex at first glance, but fear not! We’re about to take a journey into the fascinating world of botanical classification that will help unravel these mysteries.
Understanding Plant Classification
Just like we use names to identify and differentiate each other, scientists use a classification system for plants. This system, also known as taxonomy, is based on shared characteristics among different species. By grouping these plants together, it’s easier to study their traits, understand their evolution, and appreciate their role in our ecosystems.
How Many Plant Classifications Are There?
Plant classification is hierarchical, with several levels each providing more detailed information about the plant’s family, genus, and species. The main levels which we will focus on in this blog, from broadest to most specific, are: Kingdom, Phylum (or Division), Class, Order, Family, Genus, and Species. We also have subspecies and cultivars for when we need to get super specific.
Can You Explain This To Me Like I’m 5?
Yep! To simplify things, we can apply a family analogy to the entire taxonomy of plants can help demystify the classification process and clarify how each level relates to the others. Here’s how it might look:
Kingdom: The Country
The largest group, kingdom, could be likened to the country you live in. In the plant world, we live in the kingdom of Plantae, encompassing all plants. Humans and other animals would live in the country of Animalia.
Division (or Phylum): The State
Within the country, there are states. Similarly, the kingdom Plantae is divided into several groups. These groups are called divisions or phyla, which group together plants that share some large, overarching characteristics. While there’s several “states”, two are predominately used… Angiosperms (flowering plants with enclosed seeds) and Gymnosperms (naked seeds). These two divisions account for roughly 3/4 of all classified plants.
Class: The City
Continuing the analogy, think of a “class” as a city within a state. Each city has its own distinct character, just as each class includes plants that share a set of unique characteristics. Within the “state” of Angiosperms, the Elderberry resides in the “city” of Eudicots. This specific class includes a vast majority of flowering plants, known for having two seed leaves (cotyledons). Seed leaves or false leaves are the first leaves that form that don’t synthesize light. That’s why we usually wait for the second set of “true leaves” to form before transplanting a seedling.
Order: The Neighborhood
Within a city, you have neighborhoods. In plant taxonomy, orders are like neighborhoods within the city (class). They group together families of plants that share common traits. Our Elderberry’s “neighborhood” is the Dipsacales order. Plants in this neighborhood are known for their specific arrangement of flowers and often, but not always, their preference for temperate climates. Things are starting to get more specific now. Where divisions can be made up of groupings of hundreds of thousands of plant species, we're now looking at divisions in the thousands or less
Family: Your Extended Family
Then, you have your extended family, like all the cousins, uncles, aunts, and grandparents. This correlates to the ‘family’ level in plant taxonomy, grouping similar genera (plural of genus). Here we are at the family reunion of Adoxaceae! This plant family which has around 200 species includes elderberries, viburnums, and a few others. These plants often share characteristics like five-petaled flowers.
Genus: Your Immediate Family
Just as your immediate family shares your last name such as John “Smith” and a close genetic connection, all plants within a genus share a close relationship and certain defining characteristics. Now we’re getting to our Elderberry’s closest relatives, the other members of the Sambucus genus. These are all the elderberries of the world.
Species: Individual Family Members
And finally, within your immediate family, each person is an individual. It’s John from the Smith family. That’s what a species is - individual types of plants within a genus. Each species has its own unique traits that distinguish it from its siblings. And finally, we’ve found our specific plant, Sambucus canadensis, also known as the American Black Elderberry. It’s distinguished from its close relatives by its native range (largely North America), its tendency to form colonies, and the lovely dark berries it produces.
By thinking about plant taxonomy using geography and a family tree, it can become easier to understand the relationships and levels of classification.
What About Cultivars?
Now, let’s move onto something fascinating: the naming of cultivars, or as they’re also known, “cultivated varieties”. Picture this: you’re a plant breeder and you’ve just created a new variant of a plant that you want to share with the world. What do you do? You name it, of course!
The naming of cultivars follows a special set of rules set out by a group of wise plant people from the International Code of Nomenclature for Cultivated Plants (ICNCP). These rules include a unique name within the species, for the name to be placed in a single quotation and the first letter capitalized. For the elderberry cultivar “York”, it would be written as Sambucus canadensis ‘York’ or Sambucus canadensis cv. ‘York’. All you have to remember is that if you see a ‘ ‘ at the end, it is a cultivar or selectively bred plant.
Just like in the animal kingdom, there are also hybrid plants. These are the result of crossing two different species, either naturally or with a little help from human gardeners. For instance, if you cross a raspberry and a blackberry, you get a loganberry.
When it comes to the scientific names, hybrids are often denoted by an ‘x’ in the name. Where the ‘x’ gets placed will depend on what the plant is a cross between. If it’s two plants in the same genus, it will be in the middle. For example, if you cross a lemon with a mandarin orange, you would get Citrus x meyeri which is a Meyer’s lemon. If you cross two plants from different genus, the ‘x’ will be at the beginning (x Fatshedera lizei). Regardless, just know that x = hybrid.
The Importance of Genus and Species
While scientific names are super useful for scientists, for most of us, the common names of plants are easier to remember. In everyday conversation, it is so much easier to just refer to a plant as stinging nettle or white sage, but issues can arise with that. These names can vary from region to region - for instance, what's known as a "cougar" in one part of North America might be called a "mountain lion" or "puma" elsewhere. The same goes for plants. The plant commonly known as a “Black-eyed Susan” in one part of the world might be called something completely different in another region. This is why scientists and horticulturists often use the universal genus and species names when referring to plants.
The precision of these classifications ensures everyone is on the same page and knows precisely what plant is being referred to, thus avoiding any “lost in translation” moments!
Taking the Confusion Out of Plant Classification
There you have it! Just as every person at our imaginary family reunion has a unique name that describes exactly who they are in the grand family tree, every plant, from the smallest moss to the largest redwood, has a specific place in the botanical world. The scientific names, those seemingly tongue-twisting Latin terms, are our map to this diverse green universe.
Just like the way we refer to people by their first and last names to avoid confusion, plant classification works to ensure everyone— from a gardener in Oregon to a botanist in China — is speaking the same botanical language. So whether you’re calling the lovely shrub in your garden an American Black Elderberry or Sambucus canadensis, you are part of a global conversation, appreciating and preserving our natural world.
Taxonomy isn’t just a bunch of crazy names throw together; it’s a story of interconnections, a narrative of evolution, and a testament to the incredible diversity of life on Earth. So let’s embrace this language of life and let it guide us on our continuing journey of botanical exploration. Happy gardening,