A hundred years ago, you probably wouldn’t have looked twice at the rambling farmhouse on a treeless Dales landscape.

But today it stands as a striking country residence, rising from a site regarded as one of the most beautiful gardens in the north of England. Parcevall Hall Gardens at Skyreholme, near Appletreewick, started off as wild countryside and was tamed by architect and horticulturalist Sir William Milner, 8th Baronet of Nun Appleton. In 1927 he began a project to rebuild the derelict shell of a Dales farmhouse into the grand gentleman’s country residence of his dreams.

A photographic record he kept of his renovation illustrates the scope of his work. Reclaimed stone and timber were used for extensive additions to the building and Sir William, who was 6ft 4ins, had floor levels lowered by 2ft 6ins, so ceilings and doorways are unusually high for a 16th century house.

Boundaries between the house and garden are blurred, with the architecture of the building extended outwards by terraces and the stonework softened by plants. The design of the terraces and the structural links between pond, steps, walls and the house reveal Sir William’s artistry. Once completed, Parcevall Hall became his home for 30 years.

Sited at the head of a valley, the 24 acres of formal and woodland gardens has surprises at each turn; reflective pools, a splashing waterfall, streams, a herb garden, a great gateway with a gothic arch leading to an inner courtyard, specimen trees and shrubs collected from Western China and the Himalayas, a rock garden containing more than 1,000 plants, considered to be the finest of its type in Northern England, an historic rose garden and a large apple collection.

The colourful, intricate terraces allow visitors to appreciate the surroundings. A cliff walk overlooks Nevison’s Leap which, legend has it, was cleared in a single stride by highwayman Will Nevison, escaping pursuing arms of the law after taking refuge in the hall.

Today the gardens are tended by a team headed by Phillip Nelson, a former Nottinghamshire coalface worker who has been at Parcevall for 20 years. He’s also a team leader with the Upper Wharfedale Fell Rescue Team, on 24-hour call. He can be up to his elbows in soil in the garden then, if an emergency call comes in, he’s dangling from a Sea King helicopter over Penyghent, or heading underground to rescue a potholer.

“We’re one of only three teams in the UK that do above and below ground rescues,” he says. “We work with the RAF and the fire service, pumping out flooded caves and winching people to safety. I’ve even been called out to a cave rescue on Christmas Day!

“One advantage of going out on a helicopter rescue is that I get to see Parcevall gardens from the air.” Phillip is full of admiration for Sir William’s achievements. “What he did was extraordinary,” he says. “He had 13 gardeners but none of the machinery we have today.”

Today the hall is leased to the Bradford Diocese as a retreat centre and isn’t open to visitors. But Grade II listed Parcevall Hall Gardens are the largest gardens open to the public in the Yorkshire Dales.

This year marks the 50th anniversary of the death of Sir William, regarded by many as one of the most underrated horticulturists of the 20th century. The recent discovery of lists of plants sent to him from the Edinburgh Botanical Gardens for Parcevall places him alongside the most eminent plant collectors of his time.

“He was highly respected as a man who could be trusted to nurture and develop the fine plant species given to his care,” says Phillip. “In his 30s and 40s he part-sponsored plant-hunting expeditions and was a keen rhododendron collector; he grew and hybridised his own rhododendrons which don’t exist anywhere else in the world.”

The portrait which emerges of Sir William is of a kindly man who loved his house and garden and was quietly proud of what he created there.

“He was very much involved in the horticulture of his day but, sadly, he has slipped out of horticultural references,” says Phillip. “At 6ft 7ins, he had a formidable physical presence but was very low key. He was a gentle giant; despite his title and having Queen Mary, a frequent visitor to Parcevall Hall, as his Godmother, he was a reluctant socialite. His passion was gardening, he wasn’t interested in making a name for himself.”

At Parcevall, Sir William’s aim was to create a garden in harmony with the surrounding landscape, which he took full advantage of. Rocks for the rockery were dug up from surrounding fields.

Each section of garden is characterised according to underlying geology and soils, microclimate and plantings.

“The North Craven Fault goes west across the garden, leaving bedrock limestone at the surface. There are very few such natural limestone rockeries in Britain. Further on you’re back to gritstone again, where the acidic soil is good for rhododendrons,” says Phillip. “Sir William knew the benefits of both acid and alkaline soil to gardening. At the bottom of the hill there’s damper soil, where there’s a vegetable garden. There used to be a walled kitchen garden.”

The garden rises up the hillside, commanding spectacular views of Simon’s Seat and Skyreholme Beck down to the Wharfe valley, with Bolton Abbey Moor on the horizon. Phillip says Sir William was also conscious of the view of the garden itself.

“He built woodlands on what was originally pasture land with no trees; where he stood, in the 1930s, he would have been able to see for miles around. Now there’s a wood, which is 80 years old but could be mistaken for ancient woodland,” he says. “There are 1,200 native trees planted along the woodland walk, as well as plants that aren’t native to the UK. This attracts more varied birdlife.”

In later years Sir William was a friend and mentor to TV and radio gardening expert Geoffrey Smith. His final project was, as a founder member of the Northern Horticultural Society, pioneering the establishment of Harlow Carr Gardens near Harrogate. Many plants there came from the Parcevall gardens.

In 1947 Sir William, a staunch Catholic, founded a charitable religious company, Walfingham College (Yorkshire Properties) Limited, which ran the hall while he continued to live there.

After Sir William’s death in 1960 the hall was leased to Bradford Diocese. The gardens went into decline until the 1980s when Jo Makin, gardens administrator for Walfingham, took on the enormous task of renovating it.

“Everything was overgrown, it went from a fantastic garden to a broken-down mess,” says Phillip. “The renovation is ongoing, it’s constantly evolving. Our busiest period is from the snowdrops showing in early spring to the autumn colours setting in.”

  • Parcevall Hall Gardens is open until October 31, between 10am and 6pm. For more information ring (01756) 720311 or visit parcevallhallgardens.co.uk