When people see others using Latin names for plants on the forums, they often wonder why. Whether we call it a rose or Rosa rugosa, wouldn't it smell as sweet? Some say they don't care about the official names, they just want to grow pretty flowers. That's fine, but botanical Latin can be useful. Knowing a plant's genus and species helps you use resources like PlantFiles and lets you distinguish between plants with the same common name when you're trading or placing orders.
Snail Vine? Corkscrew Vine? Help!
For years, I saw this special vine in catalogs. The bloom looked lovely, and the scent sounded luscious. But some catalogs called it Corkscrew Vine, and others called it Snail Vine. I started hearing complaints that not everybody seemed to be receiving the same plant when they ordered this vine, despite the fact that the catalog descriptions and high prices were the same.
Then I discovered that two different plants, Vigna caracalla and Phaseolus caracalla, were each known by the same two common names, Snail Vine and Corkscrew Vine. No wonder there was confusion! V. caracalla has cream and purple blossoms and a strong, sweet fragrance. The purple blooms of P. caracalla lack fragrance. Both are great garden plants, but Vigna caracalla is usually the more expensive and sought-after one. Disappointed shoppers were getting "Corkscrew Vine," as promised, but they were not getting V. caracalla. Latin names do matter!
Latin names aren't just for the pros
When I joined Dave's Garden and started looking around the forums, I was a little intimidated by all the people who referred to plants by their Latin names. I was embarrassed that I didn't know the names myself, and I'd have to look them up in PlantFiles if wanted to follow the conversation. I began realizing that learning the Latin names myself would let me avoid a lot of confusion.
I decided the only way to learn these names was to make myself use them. When I organized all my seed packets into a binder with plastic pocket pages, I put them in alphabetical order by Latin name. I had to look up a lot of Latin names of common plants like columbines (Aquilegia vulgaria) and marigolds (Tagetes) in PlantFiles. Sometimes I'd have to look them up again to remind myself where to look for the seeds. But eventually, the scientific names stuck in my memory, and now I can recognize and use them.
Genus species ‘Cultivar'
When you look at the scientific name of a plant, what do the different words signify? The Latin name gives first the genus and then the species of the plant, sometimes followed by a cultivar name.
An example of this nomenclature is Heliopsis helianthoides var. scabra ‘Summer Sun'. If you know that sunflowers belong to the genus Helianthus, you'll have an idea that a flower species named helianthoides is likely to be sunflower-like. In fact, a common name for this plant is False Sunflower.
Latin names are generally either italicized or underlined. The genus name (the first word) is capitalized and may be abbreviated (as in V. caracalla). Where applicable, subspecies may be indicated by the Latin abbreviation "var." If a specific cultivar of the plant is specified, the cultivar name is in regular type and is set off by single quotation marks.
Same name, different plant?
I often suggest that people mark seed packets with Latin names as well as common ones. With the Latin name, I know I can find all the information I need in PlantFiles. A surprising number of plants with very different heights, habitats, and growing requirements have the same common name. If you search PlantFiles for "Daisy," you'll find 649 entries!
I had a mystery swap packet labeled "Milkweed," potentially containing seeds for one of over 75 species of Asclepias. A. incarnata is hardy and likes water. A. syriaca is drought tolerant, 4-6 feet tall, and can be hard to dig out once established. A. curassavica is tropical. Some species are native prairie plants or have other special requirements. So many possibilities! If I'd known what I had, maybe I'd have been able to persuade a seed to germinate.
Communicating across borders
Although most of the members of Dave's Garden live in the United States, we have a growing international membership. Scientific names are invaluable when communicating across linguistic and cultural barriers. On a recent airline trip, I sat next to a woman from the Netherlands. We had just enough language in common to discover a mutual interest in gardening, but to our dismay many flower names just didn't translate well. If we hadn't known some Latin names, our conversation would have been very brief.
Latin is used for scientific names because it's a "dead," unchanging language. Whether you are researching 200 year old plantation records, reading a German botanical journal, or buying seeds from Thailand, the Latin name will tell you exactly what plant is being discussed.
Taxonomy - the classification of living things
Every plant has a place in a whole series of categories - from kingdom to phylum, class, subclass, order, family, and finally to genus and species.  A species is generally defined by reproduction: plants within the same species can cross and produce fertile offspring. Plants in the same genus are closely related, but usually can't interbreed. Within a species, named cultivars have distinctive characteristics that "come true" from one generation to the next, either from seed or by vegetative propagation.
Just do it!
You don't have to try to learn the Latin names of every plant in your garden all at once. Look up a couple of botanical names when you're sorting your seeds. When you search for information in PlantFiles, don't just skip over the family, genus, and species names at the top. After a while, the names will become familiar, and they won't seem so awkward to use. Then, you'll start to appreciate their usefulness. What's in a name? Actually, quite a lot!
I'd like to thank the following DGers for contributing the beautiful images to PlantFiles that appear above: Todd_Boland (Rosa rugosa 'Therese Bugnet'), Kniphofia (Asclepias incarnata), Justaysam (Phaseolus caracalla), and Dave (Vigna caracalla). The other photos were taken by me in my garden.
 For more information on plant taxonomy, see "Botanical Latin for the Plebian Reader," an article by Jeffery Goss in Countryside Magazine.
(Editor's note: This article was originally published on March 4, 2008. Your comments are welcome, but please be aware that authors of previously published articles may not be able to respond to your questions.)