Return of Milk Parsley to East Yorkshire
A rare wetland plant, milk parsley, is being reintroduced to East Yorkshire to support the nationally scarce swallowtail butterfly.
Milk parsley, which thrives in marshy environments, was once common around Hornsea Mere but has experienced a significant decline in recent decades.
If this planting initiative proves successful, conservationists anticipate it could facilitate the return of the swallowtail butterfly—the largest native butterfly in the UK—to the area for the first time in over 100 years.
Historical Context and Conservation Efforts
John Barnard, a wetland specialist, explained the historical significance of the species in the region.
"There are historical records of swallowtails right across East Yorkshire. So bringing milk parsley back basically puts things in place for where they originally lived."
The Wildlife Trusts note that swallowtails are among the most localized butterflies in the UK, currently confined to the Norfolk Broads, where they attract visitors nationwide between late May and mid-July.
Milk parsley serves as the key food plant for swallowtail larvae and was once part of East Yorkshire's natural fen landscape until extensive drainage projects in the 18th and 19th centuries drastically reduced its presence.
Partnership and Seed Collection
The conservation programme is a collaborative effort between the Wassand Estate, which overlooks Hornsea Mere, and Yorkshire Water's Tophill Low Nature Reserve.
In 2024, John Barnard from Tophill Low began collecting seeds from the few remaining milk parsley plants at Hornsea Mere, cultivating a new batch genetically true to the original local population.
John Barnard commented on the challenges faced by the plant in the past.
"They struggled in the past because in the 1700s, when the Dutch came over and started draining all of East Yorkshire, the wetlands dried out and the plant largely died off," John said.
Planting and Habitat Protection
Staff and volunteers from the Wassand Estate are currently establishing the nursery-grown milk parsley plants at Hornsea Mere.
Hornsea Mere is surrounded by reedbeds, marshes, grassland, and mature woodland. It is designated both as a Site of Special Scientific Interest and a Special Protection Area due to its importance for rare and migratory bird species.
Conservationists emphasize that restoring milk parsley is a vital initial step in reintroducing the swallowtail butterfly, as the species cannot breed without this plant.
The milk parsley is also being planted in other locations across the River Hull catchment area, creating a broader network of wetland habitats necessary for the swallowtail's eventual return.
Future Prospects for Swallowtail Reintroduction
Conner Peters from Groundwork Yorkshire, involved in the restoration of Hornsea Mere, noted that reintroducing the butterfly will require time and patience.
"Potentially, in five years, that's the earliest point we think a reintroduction would be possible, because we're still in the early doors of creating these plant populations."
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