A gardener friend of ours used to object to calling a plant by its Latin name. She heard it as pretense and obfuscation. But after the sage incident, she conceded that there was some point to it.

She’d graced her Thanksgiving turkey with “wild sage,” a native sagebrush, Artemisia pycnocephala, not at all a good substitute for culinary sage and not related to it, either. If she’d been naming these plants properly, she’d have known an artemisia from a salvia, and wouldn’t have been feeding her guests wormwood stuffing.

Nothing against common names, of course. There’s a glorious kind of folk poetry in them. Who could give up talking about hoary puccoon? Nak-ed ladies? How about Welcome-home-husband-though-never-so-drunk, nodding toad, sticky monkey flower, cow-itch, ear tree, Moses-in-a-boat or fetid adder’s-tongue?

But it helps to have a standardized terminology when you must bridge languages and cultures. We once heard a discussion between a landscape architect and a nursery crew conducted in imperfect English, rudimentary Spanish and botanical Latin. And it worked.

We owe our basic system of classification to the 18th century Swedish naturalist Carl Linnaeus, whose 300th birthday falls May 23. Before Linnaeus, the scientific name of a species was a long string of Latin. He boiled it down to two words: the genus and the species. Based on details of flower anatomy, he placed every species of plant in a series of nested boxes: species, genus, family, order, subclass, class, and up to the kingdom of all plants.

The system was expanded to all living things. Although Linnaeus was no evolutionist, his framework fit remarkably well with the ideas of common descent developed later by Charles Darwin. Biologists have been tinkering with the Linnaean system ever since, but the scaffolding still holds.

Both genus and species names tend to be Latin or derived from Greek and appear in italics. (Classical language is optional, though. Scientific names have commemorated friends, colleagues, patrons, spouses, places, fictional characters. There’s a whole slew of butterflies named for characters in “Lolita,” and “The Far Side” cartoonist Gary Larson is honored in the name of a louse that lives in owl feathers.) Genus is capitalized, species is not. For convenience, genus can be abbreviated to a single letter: T. rex, E. coli. An X before the genus or species name indicates a hybrid form.

Good luck on finding a consensus on how to define a species. Zoologists tend to define species in terms of whether two animal populations hybridize and produce viable offspring. It doesn’t work for plants: Some groups, like the oaks, are promiscuous hybridizers. It may help to think of a species as the smallest discrete twig on the tree of life. A genus (plural genera) groups related species; for example, most of the oaks in quercus.

There are further refinements. Botanists use a third term, the subspecies (abbreviated ssp.) or variety (var.), for populations that aren’t quite full species. A botanist might be able to explain the difference between subspecies and variety, but we can’t.

Cultivar names come from horticulture and are given to varieties produced by artificial selection. They’re like the breeds of domestic animals. The cultivar always comes last, in single quotes, as in the manzanita Arctostaphylos pajaroensis ‘Myrtle Wolf, ‘ honoring a jewel of our local native-plant enthusiasts.

Above the species level is where most of the action is nowadays. Scientists keep inventing new boxes, and moving the contents around. Genes have revealed relationships that were obscured by the structural details Linnaeus relied on. (Plant geneticists use the genes in the chloroplasts, the tiny organelles that do the work of photosynthesis.) We’ve just learned that the water lotus is not a true water lily after all, but kin to sycamores and proteas. Cucumbers and begonias are related to oaks, pitcher plants to ocotillos.

And they finally found a place to put the rafflesia, that bizarre Southeast Asian plant with the world’s largest flower. They couldn’t use chloroplast DNA; a parasite, rafflesia has lost the genes for photosynthesis. But mitochondrial genes suggest it belongs with the euphorbias: poinsettias, spurges, castor beans and all those odd succulents that look like cacti but aren’t, even though euphorbias have small flowers.

Working up through order, class and kingdom, we come to the domain.

You, your rhododendron and the mushrooms you had for dinner all belong to the domain Eucarya: Your cells all have nuclei, and that sets you apart from the bacteria that lack them.

So here’s to Linnaeus. Imagine trying to keep track of the estimated 220,000 species of flowering plants — let alone all the varieties, hybrids, and cultivars — without a standard set of terms. Wormwood for dinner would be the least of it.

source : sfgate.com