Saving the Large Blue butterfly at Collard Hill

Large Blue butterfly
Try and spot the beautiful Large Blue at Collard Hill National Trust Images / Ross Hoddinott

The Large Blue is the largest and rarest butterfly in the UK. If you're lucky enough to spot one, you'll recognise it by its jewel-like blue wings. The underside of their wings are tawny with black spots and a blush of pale blue. There was a time when the Large Blue was extinct in the UK, but thanks to careful conservation, this fragile creature is being successfully reintroduced.

We've joined forces with 22 organisations, including Butterfly Conservation, to fight for the Large Blue. The project is being led by scientists from Oxford University and the Centre for Ecology and Hydrology.

The Large Blue butterfly is a European Protected Species and a high conservation priority species with a UK Biodiversity Action Plan (BAP).

Where are the Large Blues?

We look after four areas for Large Blues. There are two on the north Cornwall coast, one on the south edge of Dartmoor, and one on Collard Hill in the Somerset Polden hills, near Glastonbury.

Encountering the Large Blue

Collard Hill is currently the only place you can freely visit this butterfly. From early June to early July we run it as an open-access site.

Over 1,000 people visit the site during the season, and nearly everyone manages to see the butterfly, as well as enjoy the views of the Somerset Levels.

When the weather is hot, Large Blues tend to be quite active, so it's a good time to see them. The hill tends to be quite busy on sunny weekends during the Large Blue season, though - so if you want peace and quiet, come early or late in the day.

How is the Large Blue population at Collard Hill?

The Large Blue was introduced to Collard Hill in 2000 and is now doing well, with numbers set to increase. The population is already one of the largest known in Europe.

The population is monitored by a ranger. In hot weather during Large Blue season, the ranger counts butterflies along a fixed route and makes detailed counts of eggs after the flight season has finished.

Of course, much depends on the weather, particularly during the flight season. Their flight season usually runs from early June to early July, with maximum numbers flying during the third week of June.

See one of Britain’s rarest butterflies in the wild

Our fact sheet has details on accessing the Large Blues at Collard Hill, including when to visit and where to park. Otherwise please call the Large Blue phone line (07824 820193) from early June through to mid-July.