A surge in the popularity of mushroom growing at home could lead to a biodiversity disaster, British garden experts have warned.
There has been an increase 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 his 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 they new mushroom beds in the Kew kitchen garden.
Researchers are investigating the beneficial interactions between plants and mycorrhizal fungi; native mushrooms can have benefits for 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 previously popular garden plants.
Once fungi are in the soil, they are very difficult to remove because they spread with small mycelium and spores, which cannot be removed. Japanese knotweed, rhododendron and bamboo are among formerly popular garden plants that eventually became invasive species, spreading across the country and harming homes and the environment.
However, native fungi should be welcomed into the garden as they feed on dead plant and animal remains and are crucial in breaking down organic matter into humus, minerals and nutrients which can then be used by plants.
Sheila Das, a garden manager at RHS Wisley, said she was concerned that exotic fungi grown in gardens could eventually spread through the soil, change 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 need to make sure when we buy grow kits that we buy from reputable suppliers.
“We are still learning a lot about the world of fungi, so accidentally introducing invasive plants into your garden (ie species that are not native to this country) can potentially unlock many issues just as we have learned from the past with invasive plants and imported plant diseases.
“Alien fungi can potentially be even more difficult to control than alien plant species as their mode of growth is so complex and they can spread very quickly through soil and other organisms.
“A lot of home kits are designed to grow indoors, but people are often encouraged to dispose of them on their compost pile or in the garden, so it’s important to have fungi that belong in the UK if we think about its full life cycle.”
Experts said that when people choose mushroom grow kits, they should be species native to the UK so they don’t spread and cause any problems.
Dr Ruth Chitty, an RHS plant pathologist, said: “There are many gaps in our knowledge about the introduction of mushroom spawn from different countries. Research has found that different populations around the world have some genetic variation, and we are not sure what impact introducing another population would have on the UK population.
“There is a possibility that the introduction of species from other countries will have negative consequences such as out-competing native species. There are mushroom grow kits for sale that contain UK collected spawn, reducing the risk to UK mushroom populations.”
At RHS Wisley, they grow locally found species such as oyster mushrooms, coral tooth fungus, turkey tail, and birch polypore hooks, to explore their benefits for plants and wildlife in the garden.
