Fungi in deadwood help orchids grow in the dark

In a forest, death feeds life. A fallen tree doesn’t end a story – it starts another. Beneath damp bark and soft moss, fungi grow, feed, and connect.

Scientists at Kobe University discovered that these fungi don’t just recycle wood; they also nourish orchid seeds so tiny they cannot feed themselves.

This link between deadwood and new growth reveals how forests quietly move carbon from decay into life.

Orchid seeds need fungi

Orchid seeds are so small they drift through the air like dust. They lack nutrients and can’t germinate alone. Fungi become their lifeline, feeding them carbon until they can grow.

The adult orchids are known to host fungi in their roots, but what about the seeds? That mystery puzzled researchers.

“Studying orchid germination in nature is notoriously difficult. In particular, the painstaking methods required for recovering their seedlings from soil explain why most earlier studies focused only on adult roots, where fungi are easier to sample,” said SUETSUGU Kenji from Kobe University.

Understanding how orchids begin their lives has always been hard. Their seeds vanish into the soil, and their partners live hidden underground. Yet, during fieldwork, Suetsugu’s team noticed something unusual.

Orchids grow near deadwood

The team kept spotting orchid seedlings close to rotting logs. They weren’t scattered across the forest – they clustered near deadwood.

“We repeatedly found seedlings and adults with juvenile root structures near decaying logs, not scattered randomly in the forest. That recurring pattern inspired us to test whether deadwood fungi fuel orchid beginnings,” said Suetsugu.

Those root structures looked like coral. The researchers realized these weren’t just roots; they were traces of the orchid’s early life. The adults that still had them seemed connected to the same wood-decaying fungi that help their seedlings grow.

Suetsugu’s group tested their idea by burying orchid seeds near and away from logs. Only the ones near rotting wood sprouted. Every successful germination happened where deadwood and certain fungi were present.

Fungi feed orchid life

The researchers examined the fungi that supported the seeds. DNA analysis showed that the seedlings relied on wood-decaying fungi like Protomerulius and Psathyrella. Those same fungi lived inside adult orchids with coral-like rhizomes.

“We were struck by how exclusive and consistent these fungal partnerships were,” said Suetsugu.

Stable isotope testing confirmed what genetics suggested – the orchids got their carbon directly from these fungi. Young plants depended on them completely.

Even mature orchids with coral-shaped rhizomes still received more than half their carbon from the same fungal partners.

This finding exposed a hidden carbon transfer. The fungi fed on deadwood, absorbed its carbon, and passed it to orchids. In the shade of the forest, where sunlight barely touches the ground, fungi replaced the role of light. The orchids were growing, not through photosynthesis, but through decay.

Fungi changed orchid evolution

This relationship may explain why some orchids gave up photosynthesis entirely. Certain species related to those in the study live only by feeding through fungi.

“The propensity of these orchids to maintain their association with wood-decaying fungi into adult life probably facilitated their evolution of full mycoheterotrophy,” Suetsugu explains. Once an orchid learned to live on fungal carbon, it no longer needed sunlight. Over generations, that dependence turned permanent.

The study also revealed that the same types of fungi recur across many orchid species. Some, like Cremastra variabilisand Oreorchis patens, evolved from green plants to fully fungal-fed orchids. The roots of that transition – literally and figuratively – may begin in the forest floor’s decaying wood.

Deadwood as a nursery

This discovery changes how scientists view decay. What appears to rot actually builds new life. The Kobe University researchers showed that orchids, fungi, and deadwood are inseparable.

“For conservation, our results mean that protecting orchids in the wild is inseparable from protecting deadwood and its fungi,” wrote the researchers.

“For ecological sciences, they reveal a hidden carbon route from deadwood to green plants, explaining how seedlings can establish themselves on dark forest floors. And they show that deadwood is not dead – it is a cradle of new life.”

This finding echoes the message of global conservation groups such as the British Ecological Society and the International Union for Conservation of Nature (IUCN), which emphasize preserving decomposing wood habitats to maintain biodiversity.

Protecting fallen trees means protecting the future of forests. A fallen trunk feeds fungi. The fungi feed orchids. The orchids grow, bloom, and scatter seeds that begin the cycle again. The forest wastes nothing – it keeps turning death into a beginning.

The study is published in the journal Functional Ecology.

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