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THERE is a plant whose flowers bloom almost underground – and that might be how it lures in its favourite pollinators, mushroom-eating flies.

The cast-iron plant ( ) has drab flowers that are often buried in leaf litter. Biologists have long been puzzled about how these subterranean flowers are pollinated. , have all been named as possible candidates.

To find out, at Kobe University and at the Forestry and Forest Products Research Institute in Tsukuba studied wild cast-iron plants. “No one had conducted direct observations in the natural habitat,” says Suetsugu.

The pair went to Japan’s Kuroshima Island, where the plants are common. Over two years, they noted the visitors to flowers, and counted how many became fruit each autumn.

While many species visited, fungus gnats were the best pollinators. These small, mushroom-eating flies adeptly navigated the flower’s petals and the flowers they visited made the most fruit (Ecology, ).

“The gnats were observed on multiple occasions departing from Aspidistra flowers with a lot of pollen grains on their bodies,” says Suetsugu.

The cast-iron plant’s flowers may have evolved to mimic mushrooms, luring hungry fungus gnats to what looks like their favourite food. The flowers are fleshy and have a “musty” smell, similar to other plants that con fungivorous insects, like the mushroom-imitating Dracula orchids. If that is true, Suetsugu says, it could explain why the flowers are near-subterranean – it would make them look more like mushrooms.

“The drab flowers are often buried in leaf litter, which may be to make them look more like fungus”

The flowers look like the only other underground flowers, Australia’s orchids, says Anne Gaskett at the University of Auckland. This may imply convergent evolution, in which unrelated species find similar solutions to problems.

This article appeared in print under the headline “‘Underground’ flower mimics mushrooms”