Gale force winds as Storm Arwen hit the UK brought down thousands of trees, including “irreplaceable” specimens, the National Trust has said.

The conservation charity said the full extent  of the damage caused by the storm was still being assessed, but restoration was likely to cost at least £3 million.

More than 50 trees were uprooted at the Trust’s Bodnant Garden in North Wales, including a 51-metre tall “champion” coast redwood, as well as many hybrid rhododendrons that are unique to the property, it said.

The devastation left staff in tears and the clear-up is expected to take several months.

At Wallington in Northumberland, thousands of trees came down as winds reached speeds of up to 98mph, including more than half of a generation of 250-year-old oak and beech trees planted by Sir Walter Calverley Blackett.

The property is without power, phone lines and water, and all footpaths are blocked, the National Trust said.

In the Lake District, the charity’s staff were still counting the number of trees brought down, but expect the final total to be in the thousands.

Hundreds of trees were lost on estates such as Wray Castle, Fell Foot and Sizergh, while at Tarn Hows, a 19th century landscape once owned by Beatrix Potter, fallen trees and debris are blocking access roads and paths.

Other National Trust properties that were badly affected include Hardcastle Crags in West Yorkshire, Erddig near Wrexham, Cragside in Northumberland and Attingham Park in Shropshire.

Andy Jasper, head of gardens and parklands at the National Trust, said the storm had delivered a “huge blow to British heritage” at Bodnant, taking down some of the most important and earliest specimen trees at the garden.

“With it being National Tree Week we had expected to be celebrating the extraordinary trees in our care – not witnessing the scale of destruction we have.

“But this week has taken on a new significance for us, and we’re asking our supporters to donate, if they can, to help us restore the places affected.”

He said the gardens and landscapes would take months to clear up, and years or even decades to fully restore – and some would not be the same again.

“We will also make sure that this restoration work is as resilient as possible to extreme weather events of this kind, which are becoming ever more common as the climate changes.”

Acting head gardener at Bodnant Garden, Adam Salvin, added: “It’s been a real shock to staff and volunteers coming in to see the devastation caused in one night. There have been tears.

“We’ve seen storms and floods here before but this damage is on a scale not seen in living memory.”

The trust is advising visitors to sites in northern Wales and England to check property websites before setting out, as some places remain closed and walking routes at others may have changed due to the damage.