Subterranean forests are not a figment of a science-fiction writer’s imagination, but actually exist.
The Hayward Gallery’s ‘Among the Trees’ exhibition in 2020 included a remarkable photograph by Rachel Sussman of a 13,000-year-old tree, Parinari capensis, growing beneath the red sandy soil of South Africa’s savannah. Or rather, it showed the uppermost crown, the only part of the tree in view.
The appearance is of a small, ground-hugging shrub, rather than the full-sized tree it really is. Sometimes these strange trees cluster together – a veritable underground forest. Botanists have a theory that their extraordinary growth pattern, seen in several species of savannah tree, is a strategy to avoid wildfires. With the trunk and most branches below the surface, they survive the flames.
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Do underground trees exist?
As well as the shrub-like Parinari capensis, two new trees species were discovered in 2023 that are nearly entirely underground.
During a National Geographic Expeditions survey of remote Angola, Kew Gardens' Dr David Goyder found two new tree species buried in the Kalahari sands; their flowers the only parts visible above ground. Trees known to this region have as much as 90% of their body mass deep under the surface – a smart adaptation to the arid surroundings, allowing them to access the small amount of moisture that ends up underground.
Baphia arenicola belongs to the bean family and is named literally “growing on sand” and has white flowers. The second tree, Cochlospermum adjanyae, has bright yellow flowers and is named after Adjany Costa, an Angolan biologist and conservationist who won the UN Young Champions of the Earth Africa prize back in 2019.
In the same year, a new palm was also discovered by Kew's research team – this time in Borneo. The palm, Pinanga subterranea, is remarkable in its ability to flower and fruit underground. This is a phenomenon only recorded so far in one other plant group (an orchid, Rhizanthella).
The P.subterranea's leaves are above ground, so can photosynthesise like other palms, but with its flowers and fruit below the surface, scientists are grappling with how it disperses its pollen.
It's possible that insects are carrying pollen from one palm's flowers to another, but for now the true workings of its pollination remains a mystery!
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Top image: a mature Pinanga subterranea tree in Gunung Niut Natural Reserve, West Kalimantan, Indonesia. Credit: Agusti Randi, CC BY 4.0, via Wikimedia Commons