To spy this palm’s blooms and fruits, start digging underground

Its subterranean flowering and seeds are rare; no other palm is known to do this

A photograph of the palm Pinanga subterranea with its green palms sprouting out from brown leaf-strewn ground.

Plants that produce their fruits or blooms underground are rare. But botanists have just reported an extremely rare version: This palm, Pinanga subterranea, does both.

Agusti Randi

Tall palm trees are a signature of Hollywood Boulevard and tropical resorts. Their relatives, however, can come in very different shapes and sizes. And one new-to-science palm shuns the limelight to an almost absurd degree. This Pinanga subterranea is not only short, but also grows its flowers and fruit entirely underground.

“We knew immediately that it’s a really odd palm,” says Benedikt Kuhnhäuser. A botanist, he works at Royal Botanic Gardens, Kew, in Richmond, England.

Botanist Paul Chai first noticed the palm in the late 1990s. This Malaysian spotted it growing in Lanjak Entimau Wildlife Sanctuary. It’s in a Malaysian part of Borneo, a Southeast Asian island. Unfortunately, Kuhnhäuser notes, Chai lost all photos of the strange plant during a later flood.

Over breakfast one day in 2018, Chai told Kuhnhäuser and other botanists about the unusual palm. Their team had been visiting Borneo at the time. Chai’s tale prompted the team to make a trek to the sanctuary. And to their surprise, they found this underground palm abundant there.

Growing anything but roots underground is rare for a plant.

There are exceptions across the plant kingdom. South-central Africa is home to an “underground forest.” Many plants there flower above ground but grow their woody parts below. Then there’s the Bornean pitcher plant. This carnivorous species buries its traps under the soil. In fact, 33 different plant families have at least one species that hides its flowers or fruits underground.

But burying both — as the newfound palm does — is exceedingly rare. Besides this species, “there’s only one other plant in the world that does this,” Kuhnhäuser says. (It’s a group of tiny Rhizanthella orchids in Australia.)

A photograph of two hands pulling Pinanga subterranea from the dirt to reach its fruit. The brown roots of the plant are visible.
Although the underground-fruiting palm Pinanga subterranea is new to Western scientists, Indigenous people (and some wildlife) have long unearthed its fruit (seen here) as a snack.Benedikt Kuhnhäuser

New to science, but not to people

Although botanists are just learning of Borneo’s unusual palm, many people were well aware of it. “Local people, especially Indigenous ones, knew the palm,” says Cibele de Cássia Silva. She’s a botanist at the University of Campinas in Brazil who did not take part in the new research.

The locals had their own names for the palm. Some even dug it up to eat its buried fruit as a snack. For Cássia Silva and Kuhnhäuser, this highlights the importance of not only working with Indigenous peoples, but also including their knowledge in research papers.

The palm’s biology also is fascinating. Plants often work hard to invite pollinators to their flowers to aid in reproduction. Many plants also depend on the wind and animals to disperse their seeds so that the species can thrive. So how does a plant pull this off when its flowers and seeds are both underground?

This palm may rely at least partially on self-pollination. Cássia Silva suspects that even underground, beetles may be able to move pollen between plants. The researchers also saw wild pigs digging up the palm’s fruits. They might help spread the palm’s seeds in their feces.

The team described the plant in the journal Palms last June. They reported on its unique biology around the same time in the journal Plants, People, Planet.

Sidonie Bellot, who works with Kuhnhäuser at Kew, is now investigating how the newly described palm may have evolved its underground lifestyle. Many of its relatives still live close to the soil, so going all the way under may not have been that large of a leap.

More Stories from Science News Explores on Plants