Why you should learn the scientific names for plants
And why common names kind of suck.
“Oh this is beautiful! Is this a Blue Torch cactus?”. The young man was holding up a Pilosocereus pachycladus.
Pilosocereus pachycladus
“That is a Pilosocereus pachycladus!”
The young man looked at me with a slightly bemused look, “that’s a long name”.
I could tell I was losing him, and I was struck once again by a sense of sadness and confusion by the obvious disinterest in the scientific name of the plant. Plant taxonomy is the study of classifying organisms and whilst at first it may seem complicated, we assure you that it’s actually a very simple and beautiful system that creates less confusion than “common” names once you learn how it works.
See the problem with common names like “Blue Torch” is that it could refer to any of the 56 scientifically accepted species of plants in the Pilosocereus genus of plants. That would be like lumping together Equus quagga (Zebra) and Equus africanus asinus (Donkey) and calling them both a “Horse” just because they belong to the Equus genus of animals.
Plant Taxonomy Crash Course
You don’t have to be a botanist to understand the basics of plant taxonomy, read on for our quick crash course.
Binominal nomenclature
The correct way to refer to a plant is to say its Genus followed by the species, this is called binomial nomenclature (literally means “two-name naming”). When written, the whole name is italicised, the first letter of the Genus name is capitalised and the first letter of the species name is always lowercase. This is an easy way to always understand which is which. For example:
Genus species
Pilosocereus pachycladus
Homo sapien
The reason we use binomial nomenclature rather than just using the species name is that a species name is not unique on its own. For example; disciformis is a species name shared by both Melocactus disciformis and Strombocactus disciformis, two different and completely unrelated plant species. If you just said “disciformis” people would have to guess what you mean, but there is only one, and will only ever be one Strombocactus disciformis.
Another correct way to refer to a plant is to just include the first letter of the Genus, for example M.disciformis and S.disciformis are both correct.
Why the Latin?
Because it’s a dead language. Dead languages are great for scientifically naming things because they are no longer evolving and are relatively fixed in their meanings. Ancient greek is also sometimes used in plant taxonomy for this reason.
Sometimes plants are named after people but this is a horrible and self-centred idea that partly defeats the purpose of the system. Melocactus disciformis, Pilosocereus pachycladus - sounds like a whole lot of up-tight academic nonsense, doesn't it? But it actually tells a story.
Melocactus is latin for “Melon cactus” and is in reference to the globular growth habit of all plants in the genus. Disciformis can be broken down into disci- which means “discus/disc” and -formis which means “shaped”. So put it all together: Melocactus disciformis belongs to a melon-looking genus of cacti and this particular species is noticeably disc/flat shaped.
Likewise, Strombocactus disciformis tells us that it is a disc-shaped plant species belonging to a genus of cacti which is Strombo (ancient greek for trumpet-shell, snail) shaped.
cv. Syn. var - what does it all mean?
You might have seen the following before:
Lophophora williamsii var. caespitosa
What does that all mean?
cv. stands for “cultivar” and it is a man-made cultivated version of a plant, for example: “Spiralis” is a spiralling mutation of Cereus forbesii that humans have selected and encouraged in cultivation. When labelled correctly the cultivar name will appear after “cv.”, the first letter is captialised and the word is not italisced.
var. stand for “variety” and is a naturally occurring type of plant, for example: “caespitosa” is a type of plant that produces a large number of offsets or pups. Other varieties could be due to specific flower colours, shapes or growth habits. When labelled correctly the variety name will appear after “var.”, the first letter will be lowercase and the word is always italiscised.
syn. stands for “synonym” and is quite self-explanatory. syn. is often used when a plant has recently been reclassified as is the case with Trichocereus pachanoi (now Echinopsis pachanoi) and the author wants to communicate that they are the same plant to any potential reader who is unaware of the change.
The bigger taxonomy picture
You might have heard that there are other things above Genus in the taxonomy system, like plant families - that is correct. For example, every true cactus belongs to the plant family Cactaceae. In fact, there are 8 taxonomic ranks in total, but you will very rarely ever need to know anything above Genus. However, if you’re curious, the full taxonomic system looks like this:
Domain
Kingdom
Phylum
Class (clade)
Order
Family
Genus
Species
So let’s look at an example: Strombocactus disciformis
Domain: Eukaryote (Contains basically all life you’re familiar with, only excludes bacteria and some other microorganisms)
Kingdom: Plantae (Plants)
Phylum: Angiosperms (Flowering plants)
Class (clade): Eudicots (flowering plants that have two seed leaves upon germination)
Order: Caryophyllales (pretty technical botanical distinction at this level related to its ovary)
Family: Cactaceae (Cactus)
Sub-family: Cactoideae (Biggest cactus family by a country mile, only excludes prickly pears and a few weirdos)
Genus: Strombocactus
Species: Disciformis
There is a great and memorable mnemonic to help you remember the correct order for these:
Did King Phillip Come Over For Group Study?
Or if you’re like us and need something a little crude to remember it:
Did King Phillip Come Over For Group Sex?
Still not excited about plant taxonomy?
That’s okay. Check out the short clip below featuring Joey Santore from Crime Pays but Botany Doesn’t to be convinced. When you click play it will take you to the right part of the video. The whole video is excellent though, we’d highly recommend you watch it to learn some great plant facts.
