When foraging for flowers, bees search for the familiar scents that blooms puff out into the air to attract them. Scientists call these little fragrant air pockets “odor plumes.” Once bees detect an odor plume, they start following it, flying from side to side to navigate to wherever the odor is strongest—scientists call this “casting”—until they land on a flower.

“If you think of a flower, it’s basically acting as a message beacon,” says Ben Langford, an atmospheric scientist at the UK Centre for Ecology & Hydrology, based in the United Kingdom, whose team studies how insects pollinate plants. “It’s sending out a signal to attract these pollinators.”

But human pollution—in particular ground-level ozone—is messing with the odor plumes bees love, new research published in the journal Environmental Pollution shows. Ground-level ozone, which is different from ozone found in the stratosphere, is generally produced by photochemical reactions between two classes of air pollutants: nitrogen oxide gases (emitted by cars, factories, industrial furnaces, and boilers) and volatile organic compounds (released by chemical plants, gasoline pumps, oil-based paints, autobody shops, and print shops).

The intricate relationship between flowering plants and their pollinators, including bees, has evolved over millennia, and is vital not only to all ecosystems, but also to human agriculture and crop production. An estimated 75 percent of the world’s flowering plants and some 35 percent of the food crops humans grow depend on pollinators to produce harvests. Although bees aren’t the only pollinators, more than 3,500 species of bees help ensure humans have food on their plates.

The odor plumes flowers emit are usually strong but short lived—and for a reason. A strong odor, which results from a high concentration of fragrant compounds, sends a powerful message to the bees. But as the plume drifts away from the flower, there’s no reason to send this signal anymore, as it would route the bees into the wrong direction. So the fragrant molecules quickly react with other compounds in the air and fall apart.

“This is why plants generally tend to have more reactive compounds that make up their scent,” Langford says. “If they don’t react away, that background concentration of those chemicals will just build up and then the bees won’t be able to distinguish the plume from the background.” But in the presence of ozone, the plumes degrade much faster than they normally would. Langford’s team wanted to understand how much faster they degrade, and what impact that has on the bees’ ability to follow a scent.

For their study, researchers trained the bees to recognize the odor blend of several aromatic compounds. After being exposed to the smell, the bees received a sugary reward, so they learned to associate that scent with food. Then researchers investigated how the presence of ozone affected their ability to follow that scent.

Because ozone itself is damaging to bees, researchers couldn’t expose the insects to it directly. Instead, they first used a wind tunnel—a tube about 100 feet long—to learn how ozone changed the size and shape of odor plumes; they found that plumes degraded much faster on the edges than in the middle. Then they recreated the plumes in the corresponding concentrations in the lab (but without ozone) and watched how the bees fared following the scent they had memorized.

“We wanted to separate the effect of degradation of the odor plume from any direct toxic effect,” says Langford.

The research showed that ozone pollution makes it much harder for bees to forage. In fact, bees living in highly polluted areas could likely starve, exacerbating their other woes, such as Colony Collapse Disorder. First recognized in the early 2000s, Colony Collapse Disorder is a phenomenon in which the adult honeybees disappear from the hives, almost all at the same time, which leads to a population collapse.

The only way to address the issue of contaminated odor plumes, Langford notes, is to reduce the amount of ozone in the air. It’s not just a matter of helping bees find food. It’s a matter of helping bees make food for us, too.

Lina Zeldovich grew up in a family of Russian scientists, listening to bedtime stories about volcanoes, black holes, and intrepid explorers. She has written for The New York Times, Scientific American, Reader’s Digest, and Audubon Magazine, among other publications, and won four awards for covering the science of poop. Her book, The Other Dark Matter: The Science and Business of Turning Waste into Wealth, was published in 2021 by Chicago University Press. You can find her at LinaZeldovich.com and @LinaZeldovich.

This article was previously published in Nautilus.

As trees and flowers blossom in spring, bees emerge from their winter nests and burrows. For many species it’s time to mate, and some will start new solitary nests or colonies.

Bees and other pollinators are essential to human society. They provide about one-third of the food we eat, a service with a global value estimated at up to $US577 billion annually.

But bees are interesting in many other ways that are less widely known. In my new book, “What a Bee Knows: Exploring the Thoughts, Memories, and Personalities of Bees,” I draw on my experience studying bees for almost 50 years to explore how these creatures perceive the world and their amazing abilities to navigate, learn, communicate and remember. Here’s some of what I’ve learned.

It’s not all about hives and honey

Because people are widely familiar with honeybees, many assume that all bees are social and live in hives or colonies with a queen. In fact, only about 10% of bees are social, and most types don’t make honey.

Most bees lead solitary lives, digging nests in the ground or finding abandoned beetle burrows in dead wood to call home. Some bees are cleptoparasites, sneaking into unoccupied nests to lay eggs, in the same way that cowbirds lay their eggs in other birds’ nests and let the unknowing foster parents rear their chicks.

A few species of tropical bees, known as vulture bees, survive by eating carrion. Their guts contain acid-loving bacteria that enable the bees to digest rotting meat.

Busy brains

The world looks very different to a bee than it does to a human, but bees’ perceptions are hardly simple. Bees are intelligent animals that likely feel pain, remember patterns and odors and even recognize human faces. They can solve mazes and other problems and use simple tools.

Research shows that bees are self-aware and may even have a primitive form of consciousness. During the six to 10 hours bees spend sleeping daily, memories are consolidated within their amazing brains – organs the size of a poppy seed that contain 1 million nerve cells. There are some indications that bees might even dream. I’d like to think so.

An alien sensory world

Bees’ sensory experience of the world is markedly different from ours. For example, humans see the world through the primary colors of red, green and blue. Primary colors for bees are green, blue and ultraviolet.

Bees’ vision is 60 times less sharp than that of humans: A flying bee can’t see the details of a flower until it is about 10 inches away. However, bees can see hidden ultraviolet floral patterns that are invisible to us, and those patterns lead the bees to flowers’ nectar.

Bees also can spot flowers by detecting color changes at a distance. When humans watch film projected at 24 frames per second, the individual images appear to blur into motion. This phenomenon, which is called the flicker-fusion frequency, indicates how capable our visual systems are at resolving moving images. Bees have a much higher flicker-fusion frequency – you would have to play the film 10 times faster for it to look like a blur to them – so they can fly over a flowering meadow and see bright spots of floral color that wouldn’t stand out to humans.

From a distance, bees detect flowers by scent. A honeybee’s sense of smell is 100 times more sensitive than ours. Scientists have used bees to sniff out chemicals associated with cancer and with diabetes on patients’ breath and to detect the presence of high explosives.

Bees’ sense of touch is also highly developed: They can feel tiny fingerprint-like ridges on the petals of some flowers. Bees are nearly deaf to most airborne sounds, unless they are very close to the source, but are sensitive if they are standing on a vibrating surface.

Problem solvers

Bees can navigate mazes as well as mice can, and studies show that they are self-aware of their body dimensions. For example, when fat bumblebees were trained to fly and then walk through a slit in a board to get to food on the other side, the bees turned their bodies sideways and tucked in their legs.

Experiments by Canadian researcher Peter Kevan and Lars Chittka in England demonstrated remarkable feats of bee learning. Bumblebees were trained to pull a string – in other words, to use a tool – connected to a plastic disk with hidden depressions filled with sugar water. They could see the sugar wells but couldn’t get the reward except by tugging at the string until the disk was uncovered.

Other worker bees were placed nearby in a screen cage where they could see what their trained hive mates did. Once released, this second group also pulled the string for the sweet treats. This study demonstrated what scientists term social learning – acting in ways that reflect the behavior of others.

Pollinating with vibrations

Even pollination, one of bees’ best-known behaviors, can be much more complicated than it seems.

The basic process is similar for all types of bees: Females carry pollen grains, the sex cells of plants, on their bodies from flower to flower as they collect pollen and nectar to feed themselves and their developing grubs. When pollen rubs off onto a flower’s stigma, the result is pollination.

My favorite area of bee research examines a method called buzz pollination. Bees use it on about 10% of the world’s 350,000 kinds of flowering plants that have special anthers – structures that produce pollen.

For example, a tomato blossom’s five anthers are pinched together, like the closed fingers of one hand. Pollen is released through one or two small pores at the end of each anther.

When a female bumblebee lands on a tomato flower, she bites one anther at the middle and contracts her flight muscles from 100 to 400 times per second. These powerful vibrations eject pollen from the anther pores in the form of a cloud that strikes the bee. It all happens in just a few tenths of a second.

The bee hangs by one leg and scrapes the pollen into “baskets” – structures on her hind legs. Then she repeats the buzzing on the remaining anthers before moving to different flowers.

Bees also use buzz pollination on the flowers of blueberries, cranberries, eggplant and kiwi fruits. My colleagues and I are conducting experiments to determine the biomechanics of how bee vibrations eject pollen from anthers.

Planting for bees

Many species of bees are declining worldwide, thanks to stresses including parasites, pesticides and habitat loss.

Whether you have an apartment window box or several acres of land, you can do a few simple things to help bees.

First, plant native wildflowers so that blooms are available in every season. Second, try to avoid using insecticides or herbicides. Third, provide open ground where burrowing bees can nest. With luck, soon you’ll have some buzzing new neighbors.

Stephen Buchmann is Adjunct Professor of Entomology and of Ecology and Evolutionary Biology at the University of Arizona.

This article previously appeared in The Conversation.

Chelsea Cook grew to love the low hum of the honeybees she studied as a graduate student in Boulder, Colorado. Their characteristic buzz, she learned, was audible cooperation, the result of worker bees fanning their wings at the colony’s entrance to circulate the air and cool the hive. Cook often watched as the insects responded quickly to minute adjustments in temperature: When a cloud drifted over the sun, the fanners disappeared, and when it emerged again, they promptly took up their places.

Fascinated by how strictly the insects were managing their environment, Cook conducted an experiment. “I found an old hot plate and a pickle jar, created mesh cages, put a bee inside, and heated them up,” she says. Previous research had established that honeybees regularly fan to control temperature, humidity, and carbon dioxide. But over and over, the bee on Cook’s hot plate sat still. Confused, she put two bees together. “Sure enough,” with a companion, “they fanned.” Honeybees, she found, use social information—paying attention to each other—to respond to environmental changes.¹

As global temperatures rise, understanding how bees will respond is becoming increasingly important. Back in 2006, beekeepers in Pennsylvania were mystified when their previously healthy hives suddenly emptied, a phenomenon dubbed colony collapse disorder. Beekeepers across the country soon saw similar disappearances: There were no dead bodies inside the barren hives to suggest starvation, and neighboring bees, who often rob hives, seemed to avoid the unprotected honey.

It’s a mystery that’s never been fully solved. But while reports of colony collapse disorder have waned over the last decade, the fate of bees has not improved. Honeybee mortality remains startlingly high, says Nathalie Steinhauer, the research coordinator for the Bee Informed Partnership, a nonprofit organization that started conducting extensive annual bee surveys in response to colony collapse. Steinhauer explains that for the last decade, around 30 to 40 percent of the United States’ honeybees have died every year.² While intensive management has been able to keep honeybee populations roughly stable, that’s much “higher than what beekeepers consider acceptable.” Nor are the 4,000 native bee species in North America doing any better: Nearly 1 in 4 of them is at increasing risk of extinction.³

Scientists have laid the blame for bee declines on a combination of factors, like the proliferation of pesticides, and parasites like the Varroa mite, which can carry deadly pathogens. While those are major stressors on their own, they are now exacerbated by climate change, painting a disquieting future.

“Honeybees are absolutely critical to our agriculture,” says Cook, now a biologist and founder of the Cook Lab at Marquette University in Wisconsin. Three-quarters of food crops rely on honeybees for at least some pollination,⁴ making honeybees more important than fertilizer.⁵ While some plants can self-pollinate, others, like tomatoes and potatoes, don’t release their pollen until bees arrive to vibrate their flowers⁶; others may require bumblebee saliva to encourage them to flower.⁷ Even trees previously thought to self-fertilize likely have pollinators contributing to their seed production. Yet globally, pollinators are now declining so quickly the Food and Agriculture Organization of the United Nations warns their loss may spark a food crisis.⁴

The problem extends far behind the dinner table: Over 80 percent of wild plants also depend on pollination, often from native bee species, which have evolved alongside the plants they serve. But from 2008 to 2013, wild bee populations plummeted by 23 percent.⁸ If these bees disappear, says Diana Cox-Foster, an entomologist and research leader with the United States Department of Agriculture, “the landscape would basically regress back to grassland.” Long before extinction, she worries about the feedback loops losing wild bee populations may spark: Fewer bees may encourage grass growth, for example, leading to worse wildfires. “Having healthy pollinators and pollinator plantings helps you avoid a tinderbox landscape.”

To forestall these crises, it’s critical to find ways to help bees navigate shrinking habitats and a warming world. Cook’s work is now focused on helping beekeepers manage their colonies as the climate shifts. “We’re stewards,” she says, “We have to figure out how to treat them better.”

American agriculture relies on the hard work of both managed hives and wild bees: Native bees can perform much of the pollination farmers need,⁹ and significantly contribute to crop production. But when most people think of bees, they think of the humble Apis mellifera, more commonly known as a European honeybee. They are essentially insect livestock, brought to the United States to pollinate Old World plants also introduced by colonists. They are as closely managed as other domesticated animals. Many commercial beekeepers transport their honeybee hives to multiple locations a year, servicing almond orchards in California in the early spring and returning to the Great Plains for honey production later in the summer. But for the last decade, the same number of bees have been making less and less honey—and, for beekeepers, less and less money. In 2021, because of extensive drought that withered crops across the Midwest, the USDA reported that honey production dropped by a staggering 126 million pounds, or about 14 percent per colony.

Bees’ incredible ability to transform nectar into honey has long made them humanity’s friend. But hives also rely on honey to survive long after summer blooms have faded. If flowers have died off but winter cold doesn’t set in, bees may fruitlessly keep foraging, becoming nutritionally stressed. “If they used too many resources in the fall or emerge before flowers are available to feed on in the spring, there’s phenology mismatches,” a gap in the timing between bees and the flowers they depend on, says Christina Grozinger, the director of the Center for Pollinator Research at Penn State.

In the summer, honeybee workers transition through different states as they age, working as nurse bees when they are young, and foraging when they grow older. Winter bees, conversely, are physiologically different, and can survive for months. But if the colony is actively searching for nectar into the fall, they aren’t producing winter bees, meaning they aren’t as prepared to survive the winter.

“When spring comes, the older bees die at rates that exceed the replacement rate,” says Gloria DeGrandi-Hoffman, research leader at the Carl Hayden Bee Research Center. Thirty years ago, she adds, “If you’d lose 10 percent of your colonies, that was a bad year for you.” That’s in part because, like humans, bees are more likely to get sick when they’re mingling. Longer autumns and warmer winters are also extending bees’ flying time—helping spread Varroa mites and their diseases and causing surging numbers of deaths.

These climate impacts are likely exaggerated by land use changes, which reduce bees’ ability to adapt to new challenges. The increased use of herbicides and insecticides has reduced the diversity of plants bees used to depend on, while increasing their toxic load. Neonicotinoids, a class of insecticides that affect bees’ central nervous system, are particularly harmful. Bees can be exposed simply by visiting a field where they have previously been sprayed, bringing the chemical back to the hive with them. These chemicals are now used on most corn and soybean fields in the U.S., and persist in soil for years, which is why the European Union has banned three of the most common neonics.

In the U.S., a 2020 study by Penn State researchers found that in the last two decades, the toxicity to which bees are exposed rose by 121 times in the Midwest, primarily because of neonicotinoid use.¹⁰ While exposure may not immediately kill bees, even low doses of chemicals can exacerbate other stresses.¹¹ Glyphosate, the active ingredient in Roundup, for example, severely impacts bumblebees’ ability to control their temperature.¹²

While it may be hard to parse these various harms, DeGrandi-Hoffman uses a simple metric to understand how the beekeeping industry is doing. “If you look at companies that sell packages of bees or queens, they’re sold out every year. They can’t make enough to replace colonies that are lost.”

Honeybees evolved to survive winter by huddling into a thermoregulated cluster, surrounding their queen. When anthers stop releasing pollen and petals begin to shrivel, worker bees drag the male drones out of the hive into the crisp fall air, a sacrifice completed by chewing off their wings. The test of the hive’s endurance has begun. The bees’ huddle expands and contracts. It is a dying time.

To help slow these crippling winter losses, beekeepers are increasingly turning to cold storage. When honeybees are kept artificially cold, they don’t need to forage, be treated for mites, or be fed by their keepers, cutting down on costs and reducing mortality. As natural winters warm, states like Idaho and the Dakotas have been early adopters in adapting cold vegetable storage facilities for commercial beekeeping operations. Mike Lamoreaux, a business developer at Gellert, a climate control company that started out storing potatoes, says the practice has taken off over the last decade. Lamoreaux started overwintering bees in 2014. “We’d literally go to trade shows and people would stand in line, waiting to sign up,” Lamoreaux says.

Cold storage isn’t a catch-all solution. “It’s not a hospital,” Lamoreaux says. He warns people to make sure their bees are as healthy as possible before bringing them in. Like so much in modern agriculture, there’s also a question of scale: The costs and risks of these facilities work best for large-scale operations, who can afford to lose several hundred hives if something goes wrong.

To make cold storage more accessible for hobbyists and smaller operations, Cook, along with her business partner Kimberly Drennan, an architect, recently designed a mobile climate-controlled apiary. The size of a horse trailer, it has insulated panels and smart sensors to control temperature, carbon dioxide, and humidity. After winning seed money from the USDA, along with a grant from the Advanced Industries Office of Economic Development in Colorado, their company HiveTech tested a prototype in apiaries this winter. Despite supply chain shortages, early results suggest the unit increased survival three times, compared to colonies that remained outside. Providing cold storage at home cuts down on the need to transport hives, reducing both costs and mortality, and helps beekeepers better manage mite populations and their hives’ nutrition. “It puts the control in the hands of the beekeepers,” Cook says.

These kinds of practical solutions are increasingly urgent. As honey yields drop, financial pressures on beekeepers are increasing. If apiaries can’t stay in business, their efforts to keep bee populations stable will also vanish. “By adapting management—like cold storage—we can help bees make it,” says DeGrandi-Hoffman.

Wild bees, meanwhile, have fewer ways to adapt. Grozinger’s research suggests that across the country, many places that economically depend on wild pollinators will see their populations dwindle. Grozinger and her collaborators tracked wild bee abundance across the U.S., finding many of the places where bees are declining the fastest, like California’s Central Valley, are also places that currently rely on pollinators. “This means growers will be more dependent on purchasing managed pollinators, like honeybees, to produce their crops,” she says. This imbalance is already causing declining production: In another collaborative study, she found that poor seed generation in Pennsylvania black cherry trees may be due to the loss of wild andrenid bees, one of its most important pollinators.¹³

The urgency of understanding these relationships is heightened by how quickly some of these bees are vanishing from the landscape. The first bee added to the endangered species list was the rusty patched bumblebee, a wild bee which historically ranged from the upper Midwest to the East Coast, but others may soon join it. While honeybees are social animals, the majority of the United States’ 4,000 types of native bees are solitary, meaning they don’t have the help of a hive in sharing resources. “You can think about them like a single mom,” Grozinger says, “whereas honeybees are like a village.”

Adding to their vulnerability, many native bees also specialize on a small number of plants with a short blooming season, like the Mojave poppy bee, which U.S. Fish and Wildlife Service is currently considering listing as endangered. It is the only pollinator of the bearpoppy, a scrappy yellow flower that thrives in the harsh conditions of the desert, although mining, extreme heat, and drought have recently erased the wildflower from half its range.

The decline of wild bees will affect entire ecosystems, says Ellen Moss, a research associate at Newcastle University. Rising temperatures are increasingly disrupting the plants bees rely on, leading to food shortages. Moss recently conducted a study that simulated an increase in temperature of 1.5 degrees Celsius and a 40 percent increase in rainwater, over two growing seasons.¹⁴ She found that floral abundance was reduced by almost half—causing the hard-working pollinators to visit each flower more frequently to collect the same amount of pollen or nectar, while the wildflowers themselves produced fewer seeds. “I was surprised by how strong the temperature effect on floral abundance was,” Moss says.

Moss is concerned that writ large, each of these problems—climate change, habitat fragmentation, lower flower abundance—may compound. But so far, few researchers have looked outside of agriculture at the impact on non-crop plants, just as few studies have focused on wild bees and other pollinators. “No species exist in isolation,” she says. If climate change tips the balance, “it could permanently change the composition of communities.”

Still, bee experts say it’s not too late to take steps to help wild bee populations. The silver lining is that bees reproduce quickly. “They can rebound from disaster surprisingly well,” Grozinger says. She hopes to find ways to design climate resilient landscapes for bees. “If we provide a diversity of options and identify places that may provide shelter from extreme climate variation, they can find what they need in the environment,” she says. In regions where increased rainfall is predicted, for instance, Grozinger is trying to determine where there might be natural rain shadows, preserving those key islands as habitat for pollinators. A recent study in Science suggests that conserving forage for wild bees could also minimize the toxicity of glyphosate—further highlighting the importance of wildflower plantings and conserving native habitat.¹²

Grozinger’s lab has developed a public tool where you can get a bee’s eye view of the landscape near you, gauging the quality of pollinator habitat across the U.S. and encouraging people to make bee-friendly gardens. Many efforts to increase “bee pasture,” as Cox-Foster calls it, have added rippling benefits. For example, sowing cover crops—plants intended to cover the soil rather than be harvested—under almond trees not only doesn’t compete with almond blossoms, but improves the soil quality. Similarly, adding native plantings to solar and wind farms has been highly effective at alleviating their environmental impacts.¹⁵ Even neighborhood projects to plant flowers for bees along curbs and roadways can help reduce habitat fragmentation.¹⁶ Tucked into the recent infrastructure bill is a five-year program that provides $10 million in grants to replant roadsides for pollinators, and an additional $250 million will be distributed for invasive plant removal along transportation routes.¹⁷

Helping bees navigate a quickly shifting climate is a daunting task. But as a honeybee knows well, even minute actions add up. “The reason I study honeybees is their complex societies,” Cook says. The monarchy metaphor—the queen rules the hive—is misleading. The hive’s elegant division of labor is controlled by its thousands of workers, who make decisions at a local level that, when acted out, affect the entire colony. This wasn’t inevitable; like many social insects, honeybees evolved from a solitary ancestor. To survive, they adapted to persist through difficult conditions communally. “Everyone is working toward the collective good,” Cook says. “The unit of importance for bees is its society, not the individual.” These are choices, she adds, “that change how we view solutions.”

Lois Parshley is a journalist and photographer. Follow her work @loisparshley.

This article previously appeared in Nautilus.

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2. Woods, J. US beekeepers continue to report high colony loss rates, no progression toward improvement. ocm.auburn.edu/news (2021).⤶

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10. Douglas, M.R., Sponsler, D.B., Lonsdorf, E.V., & Grozinger, C.M. County-level analysis reveals a rapidly shifting landscape of insecticide hazard to honey bees (Apis mellifera) on US farmland. Scientific Reports 10, 797 (2020).⤶

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13. McLaughlin, R., et al. Insect visitors of black cherry (Prunus serotina) (Rosales: Rosacease) and factors affecting viable seed production. Environmental Entomology 51, 471-481 (2022).⤶

14. Moss, E.D. & Evans, D.M. Experimental climate warming reduces floral resources and alters insect visitation and wildflower seed set in a cereal agro-ecosystem. Frontiers in Plant Science 13, 826205 (2022).⤶

15. Pustkowiak, S., Banaszak-Cibicka, W., Mielczarek L.E., Tryjanowski, P., & Skórka, P. The association of windmills with conservation of pollinating insects and wild plants in homogenous farmland of western Poland. Environmental Science and Pollution Research 25, 6273-6284 (2018).⤶

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Search for information on ‘self-medication,’ and you’ll likely find descriptions of the myriad ways that we humans use drugs to solve problems. In fact, the consumption of biologically active molecules — many of which come from plants — to change our bodies and minds seems a quintessentially human trait.

But plants feature prominently in the diets of many animals too. A growing body of research suggests some animals may derive medicinal benefit from plant chemistry, and perhaps even seek out these chemicals when sick. Chimpanzees eat certain leaves that have parasite-killing properties. Pregnant elephants have been observed eating plant material from trees that humans use to induce labor. You may have even seen your pet dog or cat eat grass – which provides them no nutrition – in what’s believed to be an effort to self-treat nausea by triggering vomiting.

In my research, I’ve looked at how bumble bees are affected by these kinds of biologically active compounds. With colleagues, I’ve found that certain plant chemicals naturally present in nectar and pollen can benefit bees infected with pathogens. Bees may even change their foraging behavior when infected so as to maximize collection of these chemicals. Could naturally occurring plant chemicals in flowers be part of a solution to the worrying declines of wild and managed bees?

Why do plants make these chemicals?

On top of the compounds plants make to carry out the ‘primary’ tasks of photosynthesis, growth and reproduction, plants also synthesize so-called secondary metabolite compounds. These molecules have many purposes, but chief among them is defense. These chemicals render leaves and other tissues unpalatable or toxic to herbivores that would otherwise chomp away.

Many studies of coevolution center on plant-herbivore interactions mediated by plant chemistry. An ‘arms race’ between plants and herbivores has played out over long time scales, with the herbivores adapting to tolerate and even specialize in toxic plants, while plants appear to have evolved novel toxins to stay ahead of their consumers.

Herbivores may experience benefits, costs or a combination of both when they consume plant secondary metabolites. For example, monarch butterfly larvae are specialized herbivores of milkweeds, which contain toxic steroids called cardenolides. While monarchs selectively concentrate cardenolides in their own bodies as defense against predators such as birds, they may also suffer slowed growth rate and increased risk of mortality as a consequence of exposure to these toxic compounds.

Interestingly, secondary metabolites are not only found in leaves. They’re also present in tissues whose apparent function is to attract rather than repel – including fruits and flowers. For example, it has long been known that floral nectar commonly contains secondary metabolites, including non-protein amino acids, alkaloids, phenolics, glycosides and terpenoids. Yet little is known of how or whether these chemicals affect pollinators such as bees.

Could secondary metabolites influence plants’ interactions with pollinators, just as they affect interactions with herbivorous consumers of leaf tissue? Similar to other herbivores, could bees also benefit by consuming these plant compounds? Could secondary metabolite consumption help bees cope with the parasites and pathogens implicated in declines of wild and managed bees?

Plant compounds decrease parasites in bees

With colleagues in the labs of Rebecca Irwin at Dartmouth College and Lynn Adler at University of Massachusetts, Amherst, I investigated these questions in a new study. We found that a structurally diverse array of plant secondary metabolite compounds found in floral nectar can reduce parasite load in bumble bees.

In a lab setting, we infected the common eastern bumble bee (Bombus impatiens) with a protozoan gut parasite, Crithidia bombi, which is known to reduce bumble bee longevity and reproductive success. Then we fed the bees daily either a control sucrose-only nectar diet or one containing one of eight secondary metabolite compounds that naturally occur in the nectar of plants visited by bumble bees in the wild.

After one week, we counted parasite cells in bee guts. Overall, a diet containing secondary metabolites strongly reduced a bee’s disease load. Half the compounds had a statistically significant effect on their own. The compound with the strongest effect was the tobacco alkaloid anabasine, which reduced parasite load by more than 80%; other compounds that protected bees from parasites included another tobacco alkaloid, nicotine, the terpenoid thymol, found in nectar of basswood trees, and catalpol, an iridoid glycoside found in nectar of turtlehead, a wetland plant of eastern North America.

We expected that bees might also incur costs when they consumed these compounds. But we found that none of the chemicals had an effect on bee longevity. Anabasine, the compound with the strongest anti-parasite benefit, imposed a reproductive cost, increasing the number of days necessary for bees to mature and lay eggs. Despite this delay, however, there were no differences in ultimate reproductive output in our experiment.

This research clearly demonstrates that wild bees can benefit when they consume the secondary metabolites naturally present in floral nectar. And bees’ lifetime exposure to these compounds is likely even greater, since they also consume them in pollen and as larva.

In other research, we’ve uncovered evidence that some of the compounds with anti-parasite function are sought after by bees when they have parasites, but not when they are healthy. At least in some contexts – including a field experiment with wild bees naturally infected with Crithidia bombi – bumble bees make foraging choices in response to parasite status, similar to other animals that self-medicate.

Rx for struggling bee populations?

So what about practical applications: could this research be leveraged to help declining bee populations? We don’t know yet. However, our findings suggest some interesting questions about landscape management, pollinator habitat gardening and farm practices.

In future work, we plan to investigate whether planting particular plants around apiaries and farms would result in healthier bee populations. Are native plants important sources of medicinal compounds for bees with which they share long evolutionary histories? Can farms that depend on wild bee pollinators for delivery of the ‘ecosystem service’ of pollination be better managed to support bee health?

Delivery of nectar and pollen secondary metabolites to diseased bees is likely not the only tool necessary to promote long-term sustainability of these ecologically and economically important animals. But it appears that this could be at least part of the solution. Agriculture may come full circle, acknowledging that in order to benefit from an ecosystem service delivered by wild animals, we must consider their habitat requirements.

Leif Richardson is a USDA NIFA Postdoctoral Research Fellow at the University of Vermont.

This article was previously published in The Conversation.

Urban agriculture is expected to be an important feature of 21st century sustainability and can have many benefits for communities and cities, including providing fresh produce in neighborhoods with few other options.

Among those benefits, growing food in backyards, community gardens or urban farms can shrink the distance fruits and vegetables have to travel between producers and consumers – what’s known as the “food mile” problem. With transportation’s greenhouse gas emissions eliminated, it’s a small leap to assume that urban agriculture is a simple climate solution.

But is urban agriculture really as climate-friendly as many people think?

Our team of researchers partnered with individual gardeners, community garden volunteers and urban farm managers at 73 sites across five countries in North America and Europe to test this assumption.

We found that urban agriculture, while it has many community benefits, isn’t always better for the climate than conventional agriculture over the life cycle, even with transportation factored in. In fact, on average, the urban agriculture sites we studied were six times more carbon intensive per serving of fruit or vegetables than conventional farming.

However, we also found several practices that stood out for how effectively they can make fruits and vegetables grown in cities more climate-friendly.

What makes urban ag more carbon-intensive?

Most research on urban agriculture has focused on a single type of urban farming, often high-tech projects, such as aquaponic tanks, rooftop greenhouses or vertical farms. Electricity consumption often means the food grown in these high-tech environments has a big carbon footprint.

We looked instead at the life cycle emissions of more common low-tech urban agriculture – the kind found in urban backyards, vacant lots and urban farms.

Our study, published Jan. 22, 2024, modeled carbon emissions from farming activities like watering and fertilizing crops and from building and maintaining the farms. Surprisingly, from a life cycle emissions perspective, the most common source at these sites turned out to be infrastructure. From raised beds to sheds and concrete pathways, this gardening infrastructure means more carbon emissions per serving of produce than the average wide-open fields on conventional farms.

However, among the 73 sites in cities including New York, London and Paris, 17 had lower emissions than conventional farms. By exploring what set these sites apart, we identified some best practices for shrinking the carbon footprint of urban food production.

1) Make use of recycled materials, including food waste and water

Using old building materials for constructing farm infrastructure, such as raised beds, can cut out the climate impacts of new lumber, cement and glass, among other materials. We found that upcycling building materials could cut a site’s emissions 50% or more.

On average, our sites used compost to replace 95% of synthetic nutrients. Using food waste as compost can avoid both the methane emissions from food scraps buried in landfills and the need for synthetic fertilizers made from fossil fuels. We found that careful compost management could cut greenhouse gas emissions by nearly 40%.

Capturing rainwater or using greywater from shower drains or sinks can reduce the need for pumping water, water treatment and water distribution. Yet we found that few sites used those techniques for most of their water.

2) Grow crops that are carbon-intensive when grown by conventional methods

Tomatoes are a great example of crops that can cut emissions when grown with low-tech urban agriculture. Commercially, they are often grown in large-scale greenhouses that can be particularly energy-intensive. Asparagus and other produce that must be transported by airplane because they spoil quickly are another example with a large carbon footprint.

By growing these crops instead of buying them in stores, low-tech urban growers can reduce their net carbon impact.

3) Keep urban gardens going long term

Cities are constantly changing, and community gardens can be vulnerable to development pressures. But if urban agriculture sites can remain in place for many years, they can avoid the need for new infrastructure and keep providing other benefits to their communities.

Urban agriculture sites provide ecosystem services and social benefits, such as fresh produce, community building and education. Urban farms also create homes for bees and urban wildlife, while offering some protection from the urban heat island effect.

The practice of growing food in cities is expected to continue expanding in the coming years, and many cities are looking to it as a key tool for climate adaptation and environmental justice.

We believe that with careful site design and improved land use policy, urban farmers and gardeners can boost their benefit both to people nearby and the planet as a whole.

Jason “Jake” Hawes is a PhD candidate in the School for Environment and Sustainability, at the University of Michigan. 

Benjamin Goldstein, Assistant Professor of Sustainable Systems, University of Michigan. 

Joshua Newell is a professor in the School for Environment and Sustainability at the University of Michigan.  

This article was previously published in The Conversation.

After investigating the origin of the species, Charles Darwin lunged into an exploration of something that seemed, by comparison, terribly minute: orchids. By 1862, he’d traveled the world wide and far, encountering incredible organisms like giant tortoises, seafaring iguanas, and fossils of giant ground sloths. But he couldn’t stop thinking about a delicate, white star-shaped flower he’d been sent as a gift by his acquaintance James Bateman, an English horticulturalist with a penchant for rare flora from Madagascar. The flower’s odd shape—with an extremely long nectar pouch hanging under its crown—stirred in him a deep, almost inexplicable fascination.

“Orchids have interested me as much as almost anything in my life,” Darwin wrote. In their forms, he saw a vast landscape of the forces of selective evolution, a dance they played with their environment and their pollinators. “My little darlings,” as he sometimes referred to orchids, became his model for further exploring the forces he so broadly described in The Origin of Species. Just three years after the publication of that shattering work, he had produced his tome puzzling over the multitudinous, striking habits of orchids: On the Various Contrivances by Which British and Foreign Orchids Are Fertilised by Insects, and On the Good Effects of Intercrossing.

How a single family of flowers could vary so widely—from small and frilly, almost invisible to see, to large, gaudy and with a front pouch—left Darwin baffled. He called this, and flower diversity as a whole, an “abominable mystery.” Indeed, there are upward of 28,000 species of orchids worldwide and new ones cropping up every so often—sometimes even right under our noses. They have made their homes on all contemporary continents save for Antarctica—from the Arctic north, across the equator, and reaching south through all but the tip of South America.

“I think the reason people become obsessed with them is because of that mystery: Why are there so many?” says Jamie Thompson, a life sciences researcher at the University of Bath, in the United Kingdom. Yet the scientific jury is still out—and fervently debating—how many species there are exactly, what secret makes them so brilliant at diversifying, and when and where orchids evolved in the first place. Getting to the bottom of these mysteries could help us better understand the evolutionary dynamism of this massive group of alluring plants, and how we might help them fend off upcoming decimation.

To search for answers, researchers have spent decades digging into the orchid’s past. For plants, fossil records are often hard to come by because soft organic matter is less likely to be preserved than, say, bones. To track when a plant first appeared on this planet, experts now tend to rely on phylogenetic profiling: They use DNA from different species to plot them onto a tree of life, and then use a statistical model to pull them back into the past and recreate their history. 

When, in 2015, researchers used this technique to sequence 39 species from all major orchid groups, as well as data from some fossils, their findings suggested that orchids originated between 102 and 120 million years ago, most likely in Australia.¹ Ancient orchids then spread to the tropics by making their way through Antarctica—which was then connected and flourishing with vegetation. And since then, Southeast Asia is where most of their speciation has taken place.

Or at least, this is currently the leading theory about orchid origins. It may soon be upended, though, according to new preliminary findings.² An international team of researchers has drafted a study using DNA from more than 1,900 species of orchids and pinpointed their origin north, in Laurasia, modern-day Europe, Asia, and North America. The majority of diversification happened just over the past 5 million years, their work suggests, and southern Mesoamerica, such as the lush Costa Rica and Panama, actually hosts the fastest speciation of orchids.

This paper, posted to a preprint site in September, hasn’t yet been peer-reviewed, and some outside experts don’t think this new hypothesis is any good. But Oscar Pérez-Escobar, the lead author of the study and a researcher at the Royal Botanic Gardens, Kew in the United Kingdom, doesn’t think his findings are controversial at all. “Understanding where things come from can help us understand why we have X or Y species, and why there are so many,” Pérez-Escobar says.

Today, it takes a long logbook to account for orchids’ present diversity of appearances and habits. “There’s quite a number of innovations that orchids can do that other plants can’t, or not so well,” says Katharina Nargar, an orchid researcher at James Cook University, in Australia who contributed to the new study.

The neatest and most helpful of these tricks, according to Nargar, is that more than 70 percent of orchids have developed the ability to grow out of tree trunks and branches instead of soil—a capability known as epiphytism. This allows them to exploit new territories other plants cannot use, giving them “free rein,” says Nargar. Studies suggest that epiphytism evolved independently at least 14 times throughout the orchid family tree, and epiphytic orchids are “significantly richer in species” than terrestrial ones, write the authors of one study of their diversity.³ To successfully live in trees, orchids have developed the ability to absorb moisture from the air via a succulent spongy outer coating on their stem and leaves, as well as to use their roots directly to photosynthesize. The Taeniophyllum orchid, for instance, doesn’t even have any leaves: it just uses its roots for all energy production from the sun.

For the species that haven’t evolved to live in trees, the other main running theory for their inexplicable ability to diversify lies in how specialized their flowers are at getting pollinated. For one, some orchid species are the ultimate swingers—they’re very lenient in their sex lives and can produce fertile offspring with orchids from some other species, making them more likely to reproduce and more likely to often birth unique, new hybrid species, according to Nargar.

To ensure pollination, some orchids also strike up an evolutionary deal with local fauna: The plant evolves a flower so intricate it’s only accessible to a couple types of insects, and those insects are sure to only really ever pollinate other orchids. One of these striking examples is the Angraecum sesquipedale, the orchid Darwin had grown obsessed with, which has evolved a 12-inch long and narrow satchel for its nectar so that only the Hawk moth, with an exceptionally long proboscis, can access it. Although Darwin had already mused on this possibility, the moth hadn’t yet been discovered, so his theory was only confirmed almost four decades later, in 1903.

In order to fine-tune their ability to accommodate just certain pollinators, orchids have also grown very meticulous about how they deliver their pollen gifts. Some orchids bundle their pollen in tailor-made, measured, sticky packages and fling them onto their preferred pollinators with precision so that no grains are wasted and lost along the way once they fly off, and they can only be dislodged once they reach their destination. This push to specialize pollen packaging according to available pollinators—maybe a moth, maybe a bee—has also pushed diversification. And it allows one mutant orchid to have a higher chance of having loads of offspring because less pollen goes to waste than with traditionally dispersed grains. The branch of the orchid family tree that has evolved this trick called “pollinia” has a higher speciation rate than orchids that have stuck with traditional pollen grains.⁴

To take their specialization a step further, some orchids have evolved to mimic the mate of their preferred pollinator, or their favorite snack through looks, scent, and the release of special chemicals.⁵ Unknowing insects show up on their flower crown hoping to get lucky, and get duped into picking up the flower’s pollen instead. Ophrys apifera orchids look and smell like female bees. The Hammer orchid eerily resembles a female wasp. The Satyrium pumilum orchid, in South Africa, imitates the scent of dead animals to attract fruit flies, while Disa pulchra orchids pretend to be other nectar-offering flowers, like the pink iris, to fool insects into coming looking for a sweet reward. Since bees, wasps, and butterflies alike would clock the ploy if it were too common, it’s possible this has led orchids to vary in their mimetics as much as possible, spurring the birth of so many different species and tactics.

These unique flower morphology strategies are “fundamental,” to diversification according to Dewi Pramanik, an orchid morphology researcher at the Naturalis Biodiversity Center, in the Netherlands. One of her favorites is the Serapias cordigera orchid, which has evolved to shape its hairy, burgundy flower like a comfortable resting place for the Hoplitis adunca male bee, which will conveniently stop to rest there in between bouts of foraging, accidentally pollinating the flower.

Dust-like seeds are also likely among the orchid’s arsenal for rapid diversification. A single orchid seed packet can contain up to 4 million seeds, sometimes as tiny as 0.05 mm in length—the smallest in the plant kingdom—meaning plenty can easily disperse with a single gust of wind. Although most of the dust seeds won’t ever germinate, this tiny seed technique does increase the odds for diversification compared to a plant with a heartier seed bulk because new plants can crop up quickly in new locations without too much energy expenditure, and rapidly adapt accordingly.

Though orchid excellence might not all be down to just tricks pulled by the plants themselves, according to Thompson—there are external factors at play, too. When Thompson ran another phylogenetic statistical analysis on nearly 1,500 species of terrestrial orchids, his data suggested that their diversification “exploded” specifically when temperatures started dropping across the globe, somewhere around 10 million years ago.⁶ Global cooling is 700 times more likely to have influenced the rate at which orchids speciated than just time alone, Thompson says, making orchids “the best example of climate-driven speciation.”

Unfortunately, this also suggests extra trouble for the challenges orchids will face as the world warms. “I think extinction will increase, because a lot of them are cold-adapted, and we’ve seen in Europe, how hot it’s been this year,” says Thompson. Climate changes also put orchids at additional risk due to their hyper-specializing for one pollinator that might die off or be forced out of their habitat.

Going by their evolutionary history, orchids should continue to proliferate, and we should continue to discover new ones. “If you look at the number of orchid species described against time, it’s not really showing any evidence of leveling off,” according to Thomas Givnish, a professor of botany and environmental studies at the University of Wisconsin-Madison, who penned that seminal Australia-orchid-origin research. But human-caused climate change and other habitat destruction are spelling out a different future for many of these species of flower.

Some calculations suggest that plant species are dying out at least 500 times faster than before 1900, with orchids high on the threat list. Bangladesh has lost 32 of its 188 identified orchid species since 1996; in the Czech Republic, the suitable habitat for endemic orchids has declined up to 92 percent; in Florida, the number of famed ghost orchid (the sought-after subject of The Orchid Thief) has declined by half; orchids in India are blooming earlier than they should, potentially disrupting pollination. And according to a study published earlier this year, almost 280 known orchid species are in need of “immediate conservation action” but most of these still lack adequate protection.

If most of the diversity arose in the past 10 to 5 million years, the rapid loss of species we’re experiencing now might be too late to counteract, according to Pérez-Escobar. “We are kind of stuck,” he says. “If we don’t protect the orchids that we have left, the time it will take for that orchid diversity to bounce back is millions of years.” He’s on a mission to gather additional international collaboration to sample the DNA of all existing orchid species—however many they may be—because he thinks that will help him definitively plot out the plant’s evolutionary history.

The one thing experts seem to all agree on is that perhaps the best way to come up with strategies to effectively stop orchids’ decline⁷—whether it’s going to be saving the habitats they reside in, focusing on the pollinators they rely on, cutting down on their illegal trade, or all of the above—is to somehow answer the big questions of the “abominable mystery”: What are the secrets to their success in speciation? Further parsing these details about orchid diversity can help conservationists home in on their rapid and wild evolutionary plasticity to, hopefully, give them a fighting chance at adapting to a rapidly changing world.

After all, Darwin, himself noted that orchids had been “eminently useful” for him to learn how every little element, “even most trifling details of structure,” are somehow a result of natural selection.⁸ As he writes in a letter replete with exclamation points to a fellow botanist: “The beauty of the adaptations of parts seems to me unparalleled.” 

Lead image: Rak ter samer / Shutterstock

References

1. Givnish, T.J., et al. Orchid historical biogeography, diversification, Antarctica, and the paradox of orchid dispersal. Journal of Biogeography 43, 1905-1916 (2016).

2. Perez-Escobar, O.A., et al. The origin and speciation of orchids. BioRxiv (2023).

3. Gravendeel, B., Smithson, A., Slik, G.J.W., & Schuiteman, A. Epiphytism and pollinator specialization: Drivers for orchid diversity? Philosophical Transactions of the Royal Society B 359, 1523-1535 (2004).

4. Givnish, T.J., et al. Orchid phylogenomics and multiple drivers of their extraordinary diversification. Proceedings of the Royal Society B 282, 20151553 (2015).

5. Ackerman, J.D., et al. Beyond the various contrivances by which orchids are pollinated: Global patterns in orchid pollination biology. Botanical Journal of the Linnean Society 202, 295-324 (2023).

6. Thompson, J.B., Davis, K.E., Dodd, H.O., Wills, M.A., & Priest, N.K. Speciation across the Earth driven by global cooling in terrestrial orchids. Proceedings of the National Academy of Sciences 120, e2102408120 (2023).

7. Fay, M.F. Orchid conservation: How can we meet the challenges in the twenty-first century? Botanical Studies 59, 16 (2018).

8. Darwin, C. Letter to J.D. Hooker. Darwin Correspondence Project. University of Cambridge (1862).

Sofia Quaglia is a freelance journalist writing about all things science. Her work has appeared in Discover Magazine, The New York Times, National Geographic, Guardian, and more. You can follow her on Twitter at @sofiquaglia.

This article was previously published in Nautilus.

In the lush forests of Brunei, Indonesia, and the Philippines, dwells Rafflesia, one of the most mysterious and enigmatic flowers on Earth. Parasitic in nature, the plant itself has neither leaves nor roots, living most of its life hidden from view as a web of filaments inside the vines of another plant called the Tetrastigma.

After four to six years of germination, the Rafflesia pops a bud—a brown cabbage-like sphere the size of a soccer ball—through its host’s tissue that may take up to nine months to bloom. Opening unexpectedly, almost always at night, the bud erupts into a stunning, five-lobed red blossom, over three feet in diameter—the biggest flower on the planet.

Its scent, however, makes a mockery of its beauty: Rafflesias smell like rotten meat.

Rafflesia has been known to scientists for about 200 years—and has been used in botanical medicine by the Indigenous populations of Southeast Asia for much longer. Yet, it is so rare and invisible most of the time that scientists know very little about its unusual biology.

“There are definitely more questions than answers,” says Chris Thorogood, deputy director of the University of Oxford Botanic Garden. Thorogood belongs to a niche group of scientists who call themselves Rafflesiologists. This self-selected group worries the curious flowers will disappear and take their botanical secrets with them—before they are even understood.

Scientists have cataloged 42 Rafflesia species—with new species identified every year—but most of these are edging toward extinction as humans decimate their forest habitat to clear room for agriculture. Thorogood and his team recently published a paper calling for the preservation of the species. Among other things, they suggest making the flower “an icon” for plant conservation in the Asian tropics. (It already likely inspired one of the more popular Pokémon characters, Vileplume, which scatters toxic pollen that can trigger allergy attacks.)

What we do know about Rafflesia is both majestic and macabre. Rafflesia evolved its stink to attract different types of pollinating insects—not bees or wasps, who favor fragrant blooms, but flies, which prefer foul smells. “If you want to attract a fly rather than a bee, you don’t want to smell nice,” says Thorogood. Flies prefer decomposing flesh, as that’s where they lay their eggs. With its deep red hues, even the appearance of Rafflesia’s massive flower mimics, to some extent, the flesh of a dead animal. In fact, there’s nothing there for the larvae to eat. “They may sometimes lay their eggs on the flower, and then their offspring will just perish,” Thorogood explains. It’s a bit of a dead end, as it were.

But the Rafflesiologists are still trying to figure out how the pollination process works. Rafflesia plants are either male or female, and the male ones produce a thick, sticky sludge of yellow pollen. “It looks like butter that has been left out of the fridge, when it gets really soft,” says Thorogood. As flies enter the male flowers hunting for a place to lay their eggs, the pollen rubs onto their bodies. But what happens after that is an open question: One would think the flies would then carry it to a female plant and pollinate it. But because the blooms are so rare, it’s unlikely that any flies will find one nearby, Thorogood says. The plant may produce seeds, but scientists are still debating how they disperse. Some insist that ants help spread the seeds around in the jungle. Others believe that small forest animals may swallow the seeds—and poop them out. “We don’t have a united account of how the seeds are distributed,” Thorogood admits. So far, cultivation of the plant has proven difficult.

In their study, Thorogood and colleagues outline a few avenues to saving the massive stinkers—from propagating Rafflesia outside their native places to designating habitat protections to raising awareness through ecotourism, as some local conservation groups have done. “If people don’t have an awareness or care, [the species] won’t win this battle,” Thorogood says. His team hopes that the growing conservation efforts to save the world’s biggest stinker of a flower will bear fruit. 

Lead photo by Chris Thorogood.

Lina Zeldovich grew up in a family of Russian scientists, listening to bedtime stories about volcanoes, black holes, and intrepid explorers. She has written for The New York Times, Scientific American, Reader’s Digest, and Audubon Magazine, among other publications, and won four awards for covering the science of poop. Her book, The Other Dark Matter: The Science and Business of Turning Waste into Wealth, was published in 2021 by Chicago University Press. You can find her at LinaZeldovich.com and @LinaZeldovich.

This article was previously published in Nautilus.

In June, I crossed the Atlantic with my partner for a much-needed vacation. A leg of the trip brought us to Avignon, in southern France, where in the fourteenth century, due to the fluctuations of religious and political strife, the seat of the papacy, undertook a brief exile. The medieval city is organized around the stark, towering Palais des Papes, essentially a castle, which has the vast stone walls of a Game of Thrones set piece. Visitors to the Palais are given a tablet which, carried from room to room, filters the severe chambers, with their faded tapestries and accumulated centuries of scratchiti, through a digital time machine. A dark, cavernous fireplace fills with computer-generated flames, and suddenly you are a guest in the palace kitchen, or at least, this is the intention. If the augmented reality was underwhelming, the pontifical garden were not. It revealed itself beyond the battlements and chambers. The Palais des Papes has an official website, which narrates the creation of the garden as follows:

Bishop of Avignon in 1310, Jacques Duèse became Pope John XXII in 1316 and settled in Avignon. He annexed the neighboring buildings of the episcopal palace, and had the adjacent stables rebuilt. An orchard was redeveloped in 1324: the ground was leveled, trees and lawns were planted, a watering system was put in place, a wall was built to close off the area. The foundations of the pontifical gardens [were] laid.

What I remember most about the walled garden was my first encounter with an artichoke blossom. The size of a human hand, it was a purple explosion, gorgeous and slightly frightening, the kind of organism (like a vampire squid or a banyan tree) that stretches the human formal imagination merely by existing.

In the months since my return, I kept thinking about these blossoms, the garden, and the palace walls that concealed them. The common globe artichoke is a cultivar of its parent, the wild cardoon (Cynara cardunculus), with “cardoon” referring both to this ancestor as well as, more commonly, to the leafy cardoon. This separate cultivar yields an edible stalk and leaves. The artichoke, on the other hand, was selectively bred through the Middle Ages to produce the familiar “heart,” nestled within its own palatial series of semi-edible, discretely thorned leaves. If it isn’t apparent yet, the more I thought about the artichoke, the more it came to resemble the pontifical garden in which I encountered it.

Is this a coincidence, a metaphor? The centuries-long selective breeding of the globe artichoke has been obscured over time but may have begun around the turn of the first millennium in Rome, spreading throughout the Mediterranean from there.¹ Over the next five hundred or so years, in addition to selecting for the gigantism of the head (or “heart”) of the plant, Medieval gardeners produced specimens with more, bigger, and tougher leaves. The effect was that the artichoke increasingly resembled a fortress protecting its own Edenic pleasure garden, the rich and savory heart, just as the battlements of the Palais guarded the putatively holy workings of the Papacy, not only the political and liturgical wranglings but the intellectual pursuits of church functionaries with ample downtime.

One of these pursuits was the cultivation of a philosophy eventually described as “humanism,” which sometimes resembles an ink blot more than a coherent philosophical movement. Is humanism a rejection of theology, a return to “the classics”? Is it an embrace of science, empiricism, and positivism, those means by which humans observe and measure the real, or is it a turn inward, a reliance upon the reasoning intellect? Foundationally, the major humanists display a deep commitment to reason and the rational. But given that proto-racist prejudices condemned vast populations of humans as incapable of reason, “humanism” perversely enjoyed its ascendance at the same time as the dual moral disasters of colonization and the slave trade.²

Rene Descartes, arch-rationalist, is often identified as the premier philosophical author of this solipsistic, perhaps narcissistic movement “inward,” but antecedents have been found in, for example, the ecstatic Spanish nun Teresa of Avila, whose Interior Castle conceived of meditative practice as a journey to the center of a castle.³ Earlier still, and in the city of Avignon no less, Petrarch arrived at a humanistic ethos through his engagement with Greek and Roman philosophy and literature. Petrarch worked for the church for many years, and likely passed through the walls of the Palais while developing his thoughts on the relation between self and world. Did he pass by the pontifical gardens? Did he smell the flowers?

In remembering, and meditating over, the artichoke blossom in the garden of the Palais des Papes, I have found myself building associations: artichoke, walled garden, castle, humanism, and meditation itself in certain iterations. Returning to my earlier question, I wonder if this is the human practice of metaphor-working, or whether these are all effects of a common, culturally specific, formal, and imaginary movement. It would be a medieval-feudal tendency to build castles, to protect the self through rigid battlements, and to value it above human and non-human and more-than-human others.

To speculate whether this manifests in the form of the artichoke only appears ridiculous if we do not recall that generations of selective breeding for traits desirable to humans is an ongoing practice and that humans are co-authors in the collaboration with organisms across centuries.

When I approached the artichoke blossom to look at it more closely, I noticed bees working their blissful way through the forest of the bloom for nectar and pollen.

The artichoke, to bloom, must explode beyond the walls of its own castle, in the process withholding its heart from at least one form of human enjoyment (I like mine with lemon, garlic, and olive oil). This is just a different aesthetic, a movement away from a selectively bred gustatory reward, and toward a more ancestral, non-modern beauty, a beauty that is also alien, even slightly frightening.

I am wondering now about the self, a “humanist” concept of the self as worthy of privilege and priority above and beyond the non-self, the abundant other, which we carry with us, along with perhaps a more innate and stubborn tendency to build castles—in the sky, but also everywhere else—and what it might mean to bloom away, outward, beyond. The artichoke blossom exceeds human design and desire, exploding its own battlements and thereby entering the symbiogenetic fray of interspecies collaboration. Perhaps in the blossoming of the artichoke I perceived, surprisingly enough, a revolutionary politics, one that foregoes the (always-classed, always-racialized) hierarchy of human privilege in favor of relationships of mutual care and, one might hope, healing.

Sam Stoeltje, PhD, is a professor at Utica University. He/They specialize in Religious Studies, Critical and Decolonial Theory, and Epistemic Justice.

1Gabriella Sonnante, Domenico Pignone, Karl Hammer. “The Domestication of Artichoke and Cardoon: From Roman Times to the Genomic Age.” Annals of Botany 100: 5 (2007).

2Sylvia Wynter, “Unsettling the Coloniality of Being/Power/Truth/Freedom: Towards the Human, After Man, Its Overrepresentation—An Argument.” CR: The New Centennial Review 3.3 (Fall 2003).

3Christia Mercer, “Descartes’ Debt to Teresa of Ávila, or Why We Should Work on Women in the History of Philosophy,” Philosophical Studies, vol. 174, no. 10, 2017.