You know the story: Somewhere in the mythical Mediterranean, the hero Odysseus’s scouts went ashore and ate a food that made them forget that they wanted to go home. When Odysseus found them, they wouldn’t leave. So he dragged the men, weeping, back to the ships and tied them up so they wouldn’t return to the land of the lotus-eaters.

It’s a strange passage in “The Odyssey,” — the director, Christopher Nolan, took his own approach to the subject in the newly released movie — and one of the poem’s oldest unsolved riddles: What, exactly, were the lotus-eaters eating?

To understand what species of plant might have induced such a famous stupor, The New York Times interviewed 10 experts in antiquity, botany and ancient drugs.

The trouble, it seems, starts with the word “lotus” itself.

“The ‘lotus’ in Homer’s ‘Odyssey’ likely isn’t the plant most people think of today,” said Cassandra Quave, an ethnobotanist at Emory University. It is not, for example, the sacred Asian lotus that appears in Buddhist art.

And it wasn’t the most specific of terms during the time period. “The word ‘lotus’ in antiquity is used for lots of different trees and bushes and berries. It’s like ‘mackerel,’” said Greta Hawes, an associate professor of ancient history at Macquarie University in Australia.

Knowing where the lotus-eaters lived might help narrow the candidates, but even that is up for grabs. “The poet had no particular location in mind,” according to James Diggle, emeritus professor of Greek and Latin at Cambridge.

That didn’t deter ancient Greek historians, who speculated where his ship might have landed after fierce winds blew it off course for nine days. One historian, Artemidorus, pointed to Morocco, where a juicy root grew in the desert. Strabo thought it was Djerba, an island off the coast of Tunisia that’s home to a sweet little berry.

“There’s no way you could prove it, but I don’t see why not,” said Elizabeth Fentress, an archaeologist who has studied Djerba. “It does have growing wild this plant called Ziziphus lotus, which is a sedative.” She added, “I had a friend who was into it.”

Z. lotus is a spiny shrub native to the Mediterranean and North Africa, often referred to as a jujube. It produces round yellowish fruits about the size of a cherry that can be eaten fresh or dried, or fermented into wine. With its mild sedative effects, perhaps it could have kept the lotus-eaters lounging in their peaceful apathy.

Andrew Dalby, a linguist, historian and the author of “Food in the Ancient World From A to Z,” likened the fruit to “ancient snack food.” “You eat them while walking or working or hunting,” he said.

“In this case I don’t look hard for psychoactive effects: If a wine was made from it — no reason to suppose that’s not true — there you have the effect you need,” Dr. Dalby said.

But the pages of “The Odyssey” are already practically wine-stained. Would the buzz of booze be strange enough for Homer to associate it with the layabout lotus-eaters?

“I don’t think Homer would have included an alcohol-based intoxication in this story because it would have been so run of the mill,” said Peter Struck, Vartan Gregorian professor of the humanities at the University of Pennsylvania. Whatever the lotus was, he said, “It’s more exotic, more mind-altering. It’s more happy-happy.”

Blue lotus, Nymphaea caerulea, could be just that. Depictions of the flower, used to relieve anxiety and induce sleep, have been discovered on Egyptian tombs dating back to the 14th century B.C. Higher doses are known to bring hallucinations and euphoria.

“Nymphaea is a plausible candidate because of the native distribution and the known pharmacological effects,” said Alain Touwaide, a historian of medicinal plants in the ancient Mediterranean world.

The last candidate, however, might be the most obvious: the opium poppy. Alan Sumler, author of “Intoxication in the Ancient Greek and Roman World,” noted that opium was available in the ancient world, and that habitual users consumed it several times a day.

That habit, he argues, maps onto the lotus-eaters. “They’re eating it everyday. You’re not going to eat a hallucinogen every day,” Dr. Sumler said. Men who have to be dragged back to their ships and tied down aren’t in the grip of a vision; they’re in the grip of an addiction. No other drug in the ancient world, he said, “would have had that effect.”

Kirk Freudenburg, a classicist at Yale, thinks the search for a specific plant fails for good reason. “The Lotus is to food in ‘The Odyssey’ what the Cyclops is to humans,” he said. “A thing in the mythic imagination.” It doesn’t have a real-world analog. Instead, it combines qualities that make it seem dangerous, alluring and decidedly not Greek, he said.

Which leaves the question of why anyone would try to identify the “lotus” in the first place. Dr. Struck, the University of Pennsylvania classicist, has come to find that the question is more interesting than the plant itself. “The point of a made-up story is that it makes you want to understand our world better,” he said.

Christopher Nolan’s rendition, which diverges from the classic lotus-eaters tale, is only the latest attempt. After 28 centuries, continuing to search for Homer’s lotus, is, Dr. Struck said, “a way of imagining that the magic of myth might actually be a part of our own world.”