Gardeners can buy the Franklin tree, sometimes called America's lost camellia, in selected plant nurseries, but they won’t find it in the wild. There have been no confirmed sightings in nature of the small tree with its white camellia-looking flowers since 1803, when it was last reported growing along the Altamaha River valley in coastal Georgia.

If the Franklin tree (Franklinia alatamaha, which famed plant explorer William Bartram named for his father's friend Benjamin Franklin and the river where he and his father discovered it in 1765) is available in the nursery trade, why should anyone care that it's been extinct in the wild for more than 200 years?

Because the disappearance of the Franklin tree is a symptom of a much larger and modern problem, contends Steve Buchmann, an adjunct professor in entomology at the University of Arizona. Of the world's 350,000 known flowering plant species, scientists consider 22 percent of them to be rare, threatened or endangered. That places them perilously close to suffering the same fate as the Franklin tree, Buchmann believes. It's also why he sees the Franklin tree as a poster species for the planet's imperiled plants and why he's on a mission to spread the word about what he calls the world's vanishing flowers. With luck, he might even be able to save a few from extinction.

He may need to hurry.

Plants in a mass extinction

A Cypripedium lichiangense in bloomThe Chinese lady slipper (Cypripedium lichiangense) is vanishing due to drought conditions in southwestern China and northeastern Myanmar. (Photo: Steve Garvie/flickr)

The threat facing plants that scientists have already evaluated is even more alarming than the dangers facing the world's overall plant population. The International Union for the Conservation of Nature's Red List estimates that about 54 percent of evaluated plant species — 10,584 out of 19,738 — are threatened and that 279 evaluated U.S. plants are threatened, according to the Center for Biological Conservation. Other estimates, according to the center, put the number of plants considered at risk of extinction globally at one in eight, with the number in the United States facing the same fate at one in three.

Buchmann believes that these numbers should be understood in the context that the Earth is experiencing its sixth mass extinction. While many scientists say the Earth is on the brink of a sixth extinction, Buchmann believes the planet is already there. In fact, he said, it has been going on since the start of the industrial evolution in the United Kingdom in the late 1700s.

Geologists and paleontologists attribute previous extinctions to terrestrial or extraterrestrial events such as massive asteroids slamming into the Earth, volcanic eruptions or continents drifting apart. These cataclysmic events changed living conditions on the planet so drastically and so quickly in geological terms that living things — think dinosaurs — died before they could adapt to the new living conditions.

The current extinction, Buchmann said, is different from the previous five extinctions in two alarming ways. The first is that it's causing the extinction of species at unprecedented rates. The second is that this is the first extinction that can be attributed to an anthropogenic cause. (In other words, we're responsible.)

Plants keep us alive

He's not the only one who cites humans as the cause of this extinction, which is happening faster than any previous extinctions. A study by Science Advances, for example, accentuates what the authors call "the increasing severity of the modern extinction crisis." Modern vertebrate extinctions that occurred since 1500 and 1900 A.D. would have taken several millennia in previous extinctions as opposed to the rapid decline in species that has actually occurred, the authors contend, based on their study criteria.

Thelymitra campanulata orchid As an example of the destructive nature of human activity, Buchmann points out how expanding airports and suburban sites are threatening Thelymitra campanulata, an endangered orchid and a protected species that grows only in southwestern Australia (at right). An endangered Chinese lady slipper, Cypripedium lichiangense, found in thickets and evergreen forests in southwestern China and northeastern Myanmar, he adds, is vanishing due to drought caused at least in part by human-induced climate change.

Again, someone might ask, why should anyone care that two obscure flowering plants are in danger of vanishing from the Earth? Because people don't realize how much we rely on plants to supply much of the medicine and food that keep us alive and healthy, Buchmann said. "Humans," he added, "have a disconnect with plants," a major focus of his recent book, "The Reason for Flowers: Their History, Culture, and Biology, and How they Change our Lives."

He points to Madagascar periwinkle (Catharanthus roseus), a vinca that is endemic to Madagascar and is an endangered plant, as an example of a medically valuable plant. It's the original source, he said, of the alkaloids vinblastine and vincristine, which are used in the treatment of leukemia and Hodgkin's lymphoma. Fortunately, he adds, it is widely cultivated — including in his backyard — and has naturalized in subtropical areas around the world.

People also don’t realize where their food comes from, he said. A little more than a third of the diet for the world's 7.2 billion people — about 35 percent — comes from flowering plants pollinated by bees. Plant breeders for decades have used wild relatives of agricultural crop plants to breed our modern food crops for various aspects such as cold- and disease-resistance to make them more productive so they can feed the world's growing population. In some cases, such as soybeans, breeders have created what Buchmann calls a monoculture — one giant clone — that could be in danger if there were a disastrous blight caused by something such as a fungus or a widespread insect attack that cracks into the monoculture. Without genetic diversity and wild plants as backups, he said, "we are really at risk."

Plants also have a role in how we look. The red color of the lipstick plant (Bixa orellana), which is native to Central and South America, is used in cosmetics to make lipstick. This is a plant that so far seems to cohabit easily with people, growing in a somewhat weedy manner along roadsides and villages.

How to help the flowers help us

A Madagascar periwinkleThe Madagascar periwinkle had adapted to survive in various subtropical areas, and that's a good thing as the flower is medically valuable. (Photo: Arria Belli/flickr)

Luckily, Buchmann said, there is something home gardeners can do to help save the world's vanishing flowers. He ticked off four specific things anyone could do no matter where they live:

1. Plant native wildflowers. They are hardy and adapted to local soils and climate, he said, adding that they will grow better than plants native to Asia or other countries.

2. Plant something your grandmother grew. Plants from her era, Buchmann said, may not be as showy to humans as plants from modern breeding programs, but they will be far more attractive to pollinators than today's counterparts. Grandma's plants, Buchmann said, tended to be wild plants, rich with nectar easily accessible to pollinators because the plants had few petals. By contrast, he said, modern breeding for plants such as roses has produced blooms with big flowers and 100 or more petals that pollinators can’t maneuver through to get to pollen and nectar — which Buchmann said many of the new hybrids lack if the pollinators could somehow get through the mass of flower parts.

3. Encourage more local gardeners. The best way gardeners can help turn the tide is by their sheer numbers. If millions of home gardeners across the country fill their planting beds with native plants and grandma’s favorites they could recreate connected habitats, Buchmann said. Planting milkweed, he said, is a perfect example of how to create connected way stations for the monarch butterfly.

4. Keep the pollinators in mind. When planting wildflowers and heirlooms, purchase them from nurseries in different seasons so that pollinators will find a progression of blooms throughout all growing seasons.

Inset photo of Thelymitra campanulata: Terence Doust/Wikimedia Commons