The Language of Plants

Phyllostachys edulis and Hydrangea

The plants are trying to tell us something — if only we’d learn their official language, botanical Latin.

Now, a recent book called The Gardener’s Botanical: An Encyclopedia of Latin Plant Names is nudging us to sharpen our skills (as low as $32 on Amazon). The author, Ross Bayton, earned his PhD in plant taxonomy at the University of Reading and the Royal Botanic Gardens, Kew, in England, and is now the assistant director of the public Heronswood Garden in Kingston, Wash.

Tithonia diversifolia better known as Sunflower Tree is neither a true sunflower, nor a tree. It is a species of flowering plant in the family Asteraceae.

Dr. Bayton said in a recent interview that he learned his first botanical Latin word around the age of 11, from his mother’s beloved sweet peas, Lathyrus odoratus, a plant she grew every year.

“I realized that odoratus meant fragrant, and then I saw that word on other plant labels in my own garden, like Viola odorata, Galium odoratum,” he recalled. “And that kicked it all off for me.”

In his garden, he then connected the dots of mollis, for soft (Acanthus mollis, Alchemilla mollis), and its opposite, spinosa, for spiny (Acanthus spinosus, Aralia spinosa). Now they join odoratus among the 5,000-plus entries in his illustrated dictionary.

Toxicodendron radicans is best known as "Poison Ivy" but sometimes colloquially called "Picry" or "Poison Creeper" or "Poison Vine" or "Three-leaved Ivy" or "Markweed"

Quarantine Exercise

A little botanical Latin self-study might make better use of some of your garden off-season hours during pandemic than rewatching that TV series you already rewatched (although I may do that, too). A plant’s Latin name is the only way to know for certain what you’ll be getting when you buy plants in the spring, as common names vary by region — but you have to know how to decode some of the words.

Start with the plants in your garden, Dr. Bayton suggested, or even just learn to address your houseplants by their proper names. Think floridana for Florida.

This exercise will deliver a difficult memory-fitness test, and a bit of a treasure hunt. Get to know your plants, and the sometimes-nerdy snippets of the history of our human relationship with them, too.

Pityopsis graminifolia is commonly known as "Golden Aster" but in Florida it is "Silkgrass"

Why Latin?

The language of plants is based on ancient Latin but it incorporates much ancient Greek and exists primarily as a written language. The naming system was formalized in 1753 by Carl Linneaus. But again, why Latin? Short answer: Latin names never change. So while a "Sunflower Tree" may exist in Florida, in Mexico it is called a "Tournesol" or in Central America it might be the "Golden Flower of the Incas" and in Japan it is a "Nitobe Chrysanthemum."

To avoid confusion, in Latin the Sunflower Tree will always be Tithonia diversifolia, everywhere. Tithnoia is a reference inspired by Greek mythology for Tithonus, a Trojan prince who was a love interest of Eos (the goddess of the dawn) and diversifolia for leaves and flowers that are diverse, dissimilar and facing different directions, on the same plant.

Gardeners on different continents pronounce Latin names in different ways. And while there may be an “official” way (as Dr. Bayton lists in the book), he added, “say them however you want, and most gardeners will understand you. And when searching for plant-care information online or in books, pronunciation is irrelevant.”

Cicuta maculata best known as the infamous "Hemlock"

What’s In It for Gardeners?

“Accuracy — knowing a plant’s correct name — is the key to finding out everything about it,” said Dr. Bayton, who offers the common name bluebell as one example of inaccuracy’s slippery slope.

Which bluebell? The native Eastern wildflower Mertensia virginica or Hyacinthoides non-scripta, a bulb from Western Europe and England? The Campanula referred to as Scottish bluebell, or the Australian, Texas or California bluebells, each in a different genus?

Unlike common names, which can be shared by multiple plants and vary regionally, the Latin name is universal.

But even when we know the genus, let’s graduate beyond “my hydrangea” to the other word in the Latin binomial, the species name or specific epithet that modifies it.

Hydrangea quercifolia at Rainbow Springs, Florida. Obviously that translates to "Oak-leaved Hydrangea."

Let’s get to Hydrangea quercifolia (translation: the hydrangea whose leaves resemble those of an oak, oaks being genus Quercus), helping discern it from Hydrangea paniculata (whose leaves don’t).

“Hydrangeas are a big group, and they don’t all need the same treatment,” Dr. Bayton said. “If you want to know how to prune one, there are four distinct ways — so knowing it’s a hydrangea isn’t enough information.”

(Speaking of which, What’s the common name of the genus Hydrangea? Answer: There isn’t one. “What allows a name to skip over that botanical Latin barrier and not be feared?” Dr. Bayton said of the list of plants like this, which includes Magnolia, Rhododendron, Camellia, Iris, Fuchsia and Begonia. “A handful of iconic garden plants have names that are easy to pronounce and spell, and are so widely used that they’re devoid of dread.”)

Sometimes, imprecision can be not just inconvenient — the wrong plant ordered, a plant incorrectly pruned — but potentially dangerous, he said. Although Castanea (the true chestnut) and horse chestnuts (Aesculus) share that one key word in their common names and also some traits (both are deciduous trees bearing spiny fruits), they are not related, and the latter’s fruits, also called buckeyes, are poisonous.

"Florida Finger Rot" also known as "Tread Softly" or "Bull Nettle" or any number of other variations on these names is always referred to as Cnidoscolus urens var. stimulosus by botanists.

What’s in a Name?

Most Latin names are descriptive — sometimes vividly so. Toxicodendron (the genus of poison ivy, oak and sumac) and Urtica (stinging nettles; Urtica means “to burn”) spell danger: toxicity or the risk of urticaria, a skin rash. Cindoscolus (from the Greek kindo (nettle) and scolus (thorn), referring to this plants prickly characteristics).

A species name might reveal a slightly less terrifying trait, such as flower color. Yellow may be flavus or luteus, citrinus (lemon-colored) or aureus (gold). Silver is argenteus. Red is rubrum, as in the red maple (Acer rubrum); rosy-pink, roseus. Blue shades include azureus (sky) and darker caeruleus. Purple is purpureus. White is albus; black, nigrum (black pepper, Piper nigrum).

Phlox floridana or "Florida Phlox"

Native habitats might instead be called out by descriptors like sylvatica (of the woods) or palustris (marshland), maritima (seaside) or aquatica (in water).

Some plants speak of their geographic origins. Various Eastern North American natives bear the epithets canadensis or virginiana. But occasionally this backfires: Scilla peruviana doesn’t hail from Peru, although it did travel from its southwestern European or northwest African homeland on a ship named Peru, confusing the botanist who named it. The rules of botanical nomenclature say the oldest valid species name sticks, so it is peruviana evermore.

There is even the occasional anagram, where an existing genus name is remixed to form a new, botanically related one: Saruma is a cousin of the more familiar Asarum, like the native ground-cover ginger, Asarum canadense.

Sometime taxonomists are just being clever, like the one who named a cactus genus from Argentina Denmoza, because it comes from the province of Mendoza.

Meconopsis betonicifolia better known as "Himalayan Blue Poppy." Its name is from Greek mekon for poppy, and opsis for alike. And having foilate like Betony (Stachys betonicifolia officinalis).

Eponymous Names and Language Bias

A subset of plant names — both genus and species — are commemorative, honoring the explorer who discovered them, or perhaps the person who funded the mission during which they were found.

There are plants named after politicians, after botanists, after botanist’s wives. So while the information contained in Latin names isn’t always directly helpful to the gardener, there are a lot of stories in it that explain how the world was explored and how plants were discovered.

For a deeper dive into botanical Latin read William T. Stearn's seminal 1966 text on the subject. ($35 or less on Amazon).

No surprise that they tilt heavily toward the European, where the system had its origins. Frequently honored collectors include the Scottish botanist David Douglas (the epithet douglasii, and also Douglasia, a genus of Western North American primrose relatives). The prolific British explorer Ernest Henry Wilson, who sent back thousands of plants from China, is noted by wilsonii (a Magnolia and a Picea among them), and Augustine Henry, an Irish plantsman, by henryi (including Lilium henryi).

Occasionally a local name was used, as with the Asian native plants Fatsia (from the Japanese for eight fingers, descriptive of the leaves’ lobes) and Kirengeshoma (for the Japanese words for yellow, lotus blossom and hat, describing its flowers). Catalpa sounds like botanical Latin, but it is actually an Indigenous North American name for a tree genus that includes two American species.

Women, too, are markedly underrepresented.

A lot of both the men and, especially, women honored are aristocrats or royalty. But it’s considerably rarer to find a working woman so honored.

The Florida native "Yellow Water Lily" has an obviously non-native Latin name: Nymphaea mexicana

Clivia was named for the Duchess of Northumberland, Charlotte Percy (nee Clive), the first person to bloom that South African plant brought back to England. The newly crowned Queen Victoria inspired an eponymous genus: Tropical waterlilies from the Amazon were named Victoria amazonica and put on display in the Crystal Palace in Hyde Park, London.

By contrast, Mathiasella, a plant Dr. Bayton included in the book and grows at Heronswood, honors Mildred E. Mathias, a California botanist who earned her doctorate in 1929 and in 1964 became the first woman president of the American Society of Plant Taxonomists. A botanical garden on the U.C.L.A. campus is also named for her.

So why not rename those that are not politically correct? The result would be taxonomic chaos.

With new introductions, we should give them a local name, or just describe them with the chosen Latin name.

One that can help the gardener who eventually grows them.