There is an astounding variety of palm species within the Pinanga genus, with over 140 different ones. These small, upright palms are typically found in the forest understory. The majority of these species, over 100 of them, are located in Southeast Asia, particularly in Borneo, which is considered the epicenter of their diversity.
In a groundbreaking study, researchers from the Royal Botanic Gardens, Kew, and their partners have discovered a unique member of the palm family (Arecaceae) that flowers and bears fruit almost entirely underground. Due to this extraordinary characteristic, the scientists have named this species Pinanga subterranea, with its name derived from the Latin term for underground. The study was published in the journal PALMS, with additional insights provided in Plants, People, Planet.
Native to the tropical island of Borneo in Southeast Asia, Pinanga subterranea is well-known among locals who enjoy its delicious bright-red fruits—an exquisite and juicy delicacy enjoyed in certain parts of the island. Surprisingly, scientists had previously overlooked this plant, despite having described around 300 palm species on the island. Pinanga subterranea now adds to the list of over 2,500 scientifically recognized palm species, many of which are currently threatened with extinction.
According to the international team of researchers, Pinanga subterranea can be found scattered throughout the primary rainforests of western Borneo, spanning across Sarawak in Malaysia and Kalimantan in Indonesia. Before its scientific description, the plant was known by various names in three Bornean languages, including Pinang Tanah, Pinang Pipit, Muring Pelandok, and Tudong Pelandok.
Interestingly, although Indigenous people in Borneo were familiar with the plant and its fruit, it had remained unnoticed by the scientific community—much to the surprise of the researchers. This highlights the importance of closer collaboration with Indigenous communities and their extensive knowledge of the landscape and forests. The discovery of Pinanga subterranea was initially brought to the scientists’ attention by co-author Dr. Paul Chai, a Malaysian botanist after whom the palm species Pinanga chaiana was named. Dr. Chai first encountered the palm in 1997 during a visit to Lanjak Entimau Wildlife Sanctuary in Sarawak. While he was clearing away leaf litter to capture a better photo of the palm, he noticed the exposed fruit. Several plants were present, but only one bore fruit.
In 2018, scientists from Kew, including Benedikt Kuhnhäuser, Peter Petoe, and William Baker, returned to Lanjak Entimau Wildlife Sanctuary and collected several specimens of the palm for further scientific investigation. Dr. Benedikt Kuhnhäuser, a Future Leader Fellow at RBG Kew, states, “If our Malaysian colleague Dr. Paul Chai hadn’t tipped us off, we would have likely mistaken this remarkable new species for an unremarkable palm seedling and overlooked it completely. Instead, we have scientifically described an incredibly rare case of underground flowering, known as geoflory, and the first-ever observed instance of its kind within the palm family. It truly is a once-in-a-lifetime discovery.”
Independent of the team, Indonesian researcher Agusti Randi encountered a couple of Pinanga subterranea specimens in Kalimantan in 2017. Some of them had been unearthed by wild pigs, while others appeared to have been consumed or crushed by these animals. The researchers from Indonesia, Malaysia, and Kew joined forces to officially describe this unique palm as a new species.
Pinanga subterranea initially resembles juvenile plants of other common palms found in the Bornean rainforest, which often cover the forest floor and are challenging to identify—making them negligible in botanical surveys. However, in the case of Pinanga subterranea, these seemingly juvenile plants are fully mature adults, with their reproductive parts hidden below the soil surface. Despite Dr. Chai’s tip-off, the scientists still had to prove the novelty of this species. This required meticulous examination by Pinanga expert Agusti Randi, who compared specimens of this palm with all the known Bornean species of the genus, building a compelling case for its classification as a newly discovered species.
The flowering and fruiting of plants typically occur above ground for the majority of angiosperms (flowering plants). This is crucial for pollination and seed dispersal. However, a small group of plants has evolved to flower and bear fruit underground—a phenomenon known as geoflory and geocarpy, respectively. At least 171 species across 89 genera and 33 plant families have exhibited this behavior. For example, the peanut’s flowers appear above ground, while its fruit develops underground. Nonetheless, the complete flowering and fruiting underground is extremely rare and has only been observed in the small orchid genus Rhizanthella. This behavior has puzzled scientists, as it appears to impede a plant’s ability to successfully pollinate and spread seeds. Interestingly, this phenomenon has never been observed within the palm family until the discovery of Pinanga subterranea.
With the identification of Pinanga subterranea as a newly discovered species, the authors hope to arouse the interest of other researchers who can unravel the mysteries surrounding this unique palm. Dr. William Baker, Senior Research Leader—Tree of Life at RBG Kew, comments, “After studying palms for 30 years, I continue to be amazed by the surprises they hold. This unexpected find raises more questions than answers. What pollinates this palm? How does the pollinator locate the underground flowers? How did this phenomenon evolve, and what other surprises do palms have in store for us?”
In the case of Pinanga subterranea, the combination of geocarpy and geoflory has been particularly perplexing since Pinanga species are typically pollinated by insects like bees and beetles—a task that is more challenging underground. However, despite this oddity, the scientists have observed a high number of seeds and fruit set by Pinanga subterranea, suggesting the presence of a successful pollination mechanism. The mystery behind this mechanism remains, requiring further study of the processes occurring within the soil.
On the other hand, the researchers have made progress in understanding the seed dispersal method of this plant within the rainforest. Observations have revealed that the bearded pig (Sus barbatus) digs up and consumes the fruit. Although the fruit may not possess a distinct scent perceptible to humans, the pigs’ keen sense of smell likely aids them in locating the food—similar to how truffle-hunting pigs are used. The seeds from the consumed fruit are then dispersed throughout the forest via the pigs’ droppings. In fact, the researchers have successfully cultivated seeds collected from these droppings, which have thrived at Arboretum Sylva Untan in Indonesia as part of a living ex-situ collection.
Dr. Kuhnhäuser adds, “Identifying Pinanga subterranea as a new species would not have been possible without extensive palm reference collections in botanical institutions in Indonesia, Malaysia, and at Kew. Decades of diligent collection efforts have equipped us with the knowledge to discover and describe this remarkable palm species.”
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Shambhu Kumar is a science communicator, making complex scientific topics accessible to all. His articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
