A boom in the popularity of mushroom-growing at home could lead to a biodiversity disaster, UK garden experts have warned.
There has been a rise in the number of people growing mushrooms in their gardens, and this year, the RHS Chelsea flower show’s plant of the year award included a mushroom – the tarragon oyster mushroom, thought to be found only in the British Isles – in its shortlist for the first time, despite it being a fungus, not a plant.
Scientists at Kew Gardens in south-west London say they have had an increase in inquiries about growing mushrooms in the garden after installing their new mushroom beds in the Kew kitchen garden.
Researchers are exploring the beneficial interactions between plants and mycorrhizal fungi; native mushrooms can have benefits to the soil, and symbiotic relationships with plants.
But there are fears that non-native mushrooms grown in gardens or disposed of in compost heaps could cause a biodiversity disaster similar to other formerly popular garden plants.
Once fungi are in the soil, they are very hard to remove because they spread with tiny mycelia and spores, which cannot be removed. Japanese knotweed, rhododendron and bamboo are among previously popular garden plants that have ended up becoming invasive species, spreading across the country and harming homes and the environment.
Native fungi, however, should be welcomed in the garden as they feed on dead plant and animal remains and are crucial in breaking down organic material into humus, minerals and nutrients that can then be used by plants.
Sheila Das, a garden manager at RHS Wisley, said she had concerns that exotic fungi being grown in gardens could end up spreading through the soil, altering the microbiology, and be almost impossible to get rid of.
She said: “The opportunities we have to grow edible fungi at home are extremely exciting. We should make sure when buying kits for growing that we are purchasing from trusted suppliers.
“We are still learning much about the world of fungi, so introducing alien spawn into your garden by accident (ie species not native to this country) could potentially unlock many issues just as we have learned from the past with invasive plants and imported plant diseases.
“Alien fungi could potentially be even harder to control than alien plant species as their manner of growth is so complex and they can spread throughout soil and other organisms very quickly.
“Many home kits are designed for growing indoors, but people are often encouraged to dispose of them on their compost heap or in the garden, so having fungi that belong in the UK is important when we think of its full life cycle.”
Experts have said that when people are selecting mushroom grow kits, they should be species native to the UK so they do not spread and cause any issues.
Dr Ruth Chitty, an RHS plant pathologist, said: “There are a lot of gaps in our knowledge about introducing mushroom spawn from different countries. Research has found different populations across the world have some genetic variation, and we are not sure what impact introducing a different population will have on the UK populations.
“There is a possibility that the introduction of species from other countries will have negative effects such as outcompeting native species. There are mushroom growing kits for sale that contain UK collected spawn, which reduces the risk to UK fungal populations.”
At RHS Wisley they are growing locally found species such as oyster mushrooms, coral tooth fungus, turkey tail, and birch polypore brackets, to explore their benefits to plants and wildlife in the garden.
