Most plants in the parasitic genus Rafflesia—which contains the world’s largest flower—may be at risk of extinction, new research suggests.
Often called corpse flowers or stinking corpse lilies, these blossoms are infamous for their distinctive odor of rotting flesh. Though the genus does not include the corpse flower called titan arum, known for drawing crowds to botanic gardens when it blooms once every few years, Rafflesia plants have short-lived, rancid blossoms all their own.
As of now, just one of 42 known Rafflesia species, Rafflesia magnifica, is listed as critically endangered by the International Union for Conservation of Nature (IUCN). Using the same criteria as the IUCN, a team of researchers reports that the number of listed species should be much higher, according to a new paper published last week in the journal Plants, People, Planet.
Instead, 25 Rafflesia species should be considered critically endangered, 15 endangered and two vulnerable, the scientists say—in total, that’s every species in the genus. They also predict that at least 67 percent of known Rafflesia habitats fall outside of protected areas, leaving the pungent plants even more at risk.
“Plants are crucial for our existence—the air we breathe, the food we eat and the medicines we take. Yet many people scarcely even notice them. The fact is, we are more attuned to seeing animals in the world around us,” paper co-author Chris Thorogood, deputy director and head of science at the Oxford Botanic Garden and Arboretum, tells Emma Ogao of ABC News. “But plants are the foundation for the habitats in which animals thrive.”
“My hope is that the world’s largest flowers will be a powerful new icon for plant conservation,” he adds.
The world’s largest single flower on record was from a Rafflesia arnoldii specimen discovered in an Indonesian forest in 2020. The massive blossom measured three feet and seven inches across, per the Guinness Book of World Records. An individual flower of Rafflesia arnoldii can weigh more than 20 pounds.
Rafflesia are notoriously difficult to study, complicating conservation efforts. The plants grow only in remote rainforests in Southeast Asia, have no leaves, stems or roots and do not photosynthesize. Instead, they grow as fleshy strands inside vines of the genus Tetrastigma, parasitically absorbing their water and nutrients. For most of Rafflesia’s life cycle, it remains unseen within these vines.
But after a few months or years, a golf-ball sized bud may appear on the host, per National Geographic’s Shi En Kim. From the bud, a gigantic red flower emerges and blooms for just a few days. The putrid, rotting smell attracts flies hoping to lay their eggs, and as the insects travel from plant to plant, they collect and deposit pollen. Most Rafflesia flowers are either male or female, meaning two plants with flowers of the opposite sex must bloom at the same time and within one mile of each other to successfully reproduce with the help of the flies, per National Geographic.
Much about the plants remains a mystery, including basic questions about when they tend to bloom and how many species exist. So far, researchers have failed to grow them in the lab outside of their host vine—and they cannot be propagated using usual techniques like cuttings, seeds or tissue culture, as Erika Marie Bascos, a biologist at the University of the Philippines, told Mongabay’s Mikael Francisco in July.
Authors of the new study recommend that all Rafflesia species be immediately added to the IUCN’s Red List and that conservation organizations and governments work together to increase Rafflesia research and protect their habitats, per a statement from the University of Oxford. According to the university, local ecotourism initiatives driven by the flowers’ ephemeral blooms can help protect plant populations and raise awareness of their need for conservation.
“Indigenous peoples are some of the best guardians of our forests, and Rafflesia conservation programs are far more likely to be successful if they engage local communities,” Adriane Tobias, a forester from the Philippines, says in the statement. “Rafflesia has the potential to be a new icon for conservation in the Asian tropics.”