A bald patch on the box hedge at the bottom of the garden marks the spot where "hundreds of people rest their camera bags" while they photograph the front of Plas yn Rhiw. It's just one of the things the gardener has to contend with. Another is the thousands of footsteps which wear away the grass footpaths, and the constant questions about weeds - some of which have been deliberately allowed to flourish.

Plas yn Rhiw was bought by the Keating sisters, Eileen, Lorna and Honora, and their widowed mother Constance in 1939. They set about a comprehensive programme to save the old Welsh manor house and re-create the garden, while campaigning to protect its whole environment. They bought various smallholdings in the area to restore the estate to something of its former glory (there has been a house on the site since the 14th century), and in 1946 in memory of their parents Constance and William Keating, the sisters donated surrounding land to the National Trust, followed by the house and further land in 1952. They continued to live there, however, until the death of the last sister Lorna in 1981.

It is their vision for the garden which is being continued today, complete with the wild flowers, and some say weeds, they transplanted from the wild, some of them unseen in the countryside today due to the use of herbicides. Since they started work on the garden, apart from a minor blip in the 80s when one of the beds was sprayed for pests, the garden has been run along organic principles. It's the only organic National Trust garden in Wales, and one of only three throughout England and Wales - although the other two, Trengwainton, near Penzance, and Snowshill Manor, in Gloucestershire, "haven't got the same pedigree as Plas", according to current head gardener Tim Walker.

Tim came to the garden ten years ago. He was living in Staffordshire with his wife Sally and their two young children Trystan and Alice and working for the family business as a master plasterer, but had a degree in botany. Law clerk Sally was originally from Gwynedd. It was when Trystan one day managed to get out of the house and down the road on his own that they decided they wanted to live somewhere safer for children. Within three weeks Tim had resigned from work, their house quickly sold, and they moved to a rented house near Criccieth to begin their new life, before finding Pen y Maes near Rhoslan, the dilapidated house they were looking for, so that they could "restore a bit of rural Wales". It was, says Tim, "a life-changing experience to restore a house as a key piece of history."

At about the same time he went to the gardens at Plas yn Rhiw and met Paul Lewis, The National Trust warden for the area, and did some work identifying tree plots. He also met Mrs Dick, the custodian at the time, and started volunteering in the garden. Then a few months later the gardener Robin Thomas retired and "it was suggested by someone in the Trust that I apply for the job, and I got it in 1995."

Rooted in history, the garden is run along organic lines, as it was by the Keatings, and although today it's less overgrown than it had become, many of the plants survive either in their original form, or as progeny of specimens brought in by the sisters. Large overflowing flower beds are contained by box hedges deliberately cut by the sisters in asymmetric patterns. They brought in plants from the wild such as teasles; iris pseudocrus, (which has unusual blackcurrant margins on the flowers); various poppies; myrtle; the poisonous monkshood; sheep sorrel (related to the culinary sorrel but with much smaller leaves) and foxgloves. Other 'weeds', such as the gardener's nightmare, ground elder, are welcome.

Star players in the garden include the specimen Magnolia campbelli. "It's said by sources who spoke to the sisters themselves, that the tree was grown from seed Honora was given when she visited the Far East, although we have no way of proving this," says Tim.

"The Pieris foresttii, named after another Scottish botanist, arrived in 1953. This was ordered from China and took three years to arrive, amazing when people apologise today for not getting something to you by the next day!" says Tim.

Grass footpaths take unexpected twists and turns, revealing hidden treasures, such as the first bath on the Llŷn Peninsula, bought in by a Lady Strickland who lived at the house for two summers in the late 1800s, now thrown out and used as the base for a water feature, a little summerhouse, mostly used as a plant hospital nowadays, and the two-seat outside privy. Thanks to the micro-climate exotic plants flourish in the gardens. Former gardener Robin Thomas, who lives less than two miles away, recalls of his time working at Plas yn Rhiw. "It was warm even in the winter, and I was always complaining how cold it was when I got home." In fact under the veranda at the front of the house the tender Abutilon hibridum - ashford red - flourishes, surviving outside even in Winter.

According to Tim, "This really is heaven - it's not an illusion. Within the confines of the property, everything is harmonious."