The sale of a popular Brazilian giant rhubarb will be effectively banned after a study found it to be an invasive species.
A paper from the Royal Horticultural Society has found that almost all species of the plant for sale is a cross-breed between a banned invasive variety, Gunnera tinctoria, and one that is allowed in the UK, Gunnera manicata.
The hybrid species, known as Gunnera cryptica is therefore effectively banned from sale because it is a hybrid of a species of special concern under the Invasive Alien Species Regulation.
The law means it is an offence to plant or otherwise cause Gunnera tinctoria to grow in the wild.
Gardeners will not have to dig up their giant rhubarb because no offence is committed if a listed plant is growing in your garden or on your land. However, watering the plant could fall foul of the rules on cultivating, so plants are expected to die out, according to the Guardian, which first reported the story.
“We are aware of the Royal Horticultural Society paper that states that almost all Gunnera manicata is a cross with the banned species Gunnera tinctoria,” a Defra spokesman said.
“Members of the public who identify this hybrid growing in their garden do not need to take action.
“However, you cannot intentionally plant, sell use or exchange the species given its status as an invasive alien species.”
The RHS said the hybrid arose many years ago and has remained undetected until the recent DNA research conducted by its scientists, which included molecular and morphological analyses, as well as a historical investigation.
Both varieties were introduced in the Victorian period and often found by ponds and lakes.
The two parent species and the hybrid look very similar, which the RHS said might explain how the hybrid went undetected for so long.
John David, the head of horticultural taxonomy at the RHS, said it was “a surprise to find that a plant that has been a firm favourite in our gardens for its impressive size and exotic appearance, turned out to be an undetected hybrid”.
He added: “This would not have been possible without the help of botanists in Brazil and Chile, where these plants originate, as well as many others who provided material that enabled us to prove the disappearance of one species and the discovery of the new hybrid.”