The colony, believed to be the most northern in Britain, was created after the plant was first spotted by Yorkshire-based ecologist Martin Hammond in a pool created by lorry tracks on a roadside verge near Thixendale. It is not known how the plant came to be in the Wolds, although its spores can remain dormant for decades.
Mr Hammond, working with North Yorkshire County Council’s biodiversity officer, secured funding to create a series of shallow pools in the area, in the hope that adding sediment from the original pond where the stonewort was found, would allow the plant to spread and multiply.
Now the ponds have been checked and stonewort has established in three of the nine pools - in one of them it has formed a dense sward over about four square metres.
The ponds have also been colonised by pioneer water beetles, water bugs and other aquatic life.
Chris McGregor from Natural England, which helped create the ponds alongside the county council volunteers, said: “This is a great result for one of Britain’s rarest plants.
“Using Government Environmental Stewardship funds, the ponds will be managed to maintain the open conditions that the stonewort thrives in and we will be checking on its progress.
“Volunteers and staff from Natural England and Pond Conservation have provided habitat restoration expertise and worked closely on site with the landowners who have been fully behind the work.”
North Yorkshire County Councillor Chris Metcalfe said “It is fantastic to see that the valuable work of our countryside volunteers has enabled such a rare plant to re-establish itself in North Yorkshire. It is a wonderful example of a number of organisations and the community coming together to make the countryside better for wildlife and people.”