THE leaves of many of the trees are now turning to the rich reds, golds and coppers of autumn and keen gardeners will marvel at the endless variety of trees and shrubs in one of the most comprehensive collections of hardy, woody plants in Europe. This is a dazzling display that can be enjoyed up until the end of November, when the Castle Howard Arboretum will close for the winter.

The design was the shared vision of the late James Russell and Lord George Howard, who started work on it in 1975 with the aim of creating a collection for future generations to enjoy. It was first opened to the public in 1999 as part of Castle Howard's tercentenary celebrations. Maurag Carmichael, administrator at the arboretum says: "This is our main season as everyone likes to see the autumn colours. When the sun is shining, it's glorious.

"All of the plants here have been grown from seed collected in temperate regions around the world, including China, Chile
and Japan.

"We are in a valley here on the edge of the Vale of York and seem to be sheltered from the winds that come across from the moors. We also have a great mix of soil, so if a plant isn't doing so well in one area it can be moved to somewhere more suitable."

The plant collection has immense environmental, scientific and conservational value, but the arboretum is also an idyllic spot to simply while away a couple of hours.

Visitors can pick up a map as they pay their admission fee and follow one of two trails of varying length, but it is equally pleasant to allow yourself to roam freely among the network of wide grassy pathways and see where you end up.

As you meander through a series of themed wooded areas there are surprises at almost every turn. Stunning vistas open up before you, providing breathtaking views across the site.

My favourite was the Silver Vista, a broad avenue running down the centre of the arboretum flanked on each side by silver-leaved trees and shrubs that gleamed against the cloudless blue sky. There are also hidden ponds and artworks, which form part of the new community sculpture trail opened earlier this year, as well as a serene lake and a dense bog area where the dramatic umbrella-sized leaves of gunnera manicata take centre stage.

Another surprise comes at Pear Glade, an area resembling an English orchard full of trees laden with fruit. Each plant is carefully labelled and closer inspection reveals a staggering collection of pear varieties from around the world, many of which look unfamiliar.

The policy towards dogs is a refreshing change. Not only are they welcome, but, providing they are well behaved and under control at all times, they are also allowed off their leads. Our labrador, Bobbie, thoroughly enjoyed herself and even had an impromptu dip in the lake, although this is not to be encouraged during the breeding season when ground-nesting birds may be disturbed.

At the café we selected a table outside on the decking, where we sat in the surprisingly warm late afternoon sunshine. The menu was reasonably priced and featured homemade soup, sandwiches and cakes, most of which appeared to use locally-sourced ingredients. The friendly staff made sure that we took a complimentary dog biscuit.

Located in the Howardian Hills north of York and just a stone's throw from Castle Howard itself, the arboretum is run by the Castle Howard Arboreturm Trust (CHAT), an independent charitable trust formed in June 1997 by Castle Howard and the Royal Botanic Gardens at Kew.

John Simmons, previously curator at Kew, curates the collections and Neil Batty, the leading collections arborist, oversees the day-to-day work. The trust employs only a small number of staff and relies heavily on volunteers. Maurag explained: "We have about 20 volunteers, who do everything from staffing the ticket office to taking visitors on guided tours of the site. They also help to deliver our education programme, although we appointed an education development officer two years ago. We have hosted visits from around 450 school parties."

The arboretum is open daily until the end of November and will reopen next March. It is usually open between 10am and 6pm, but will close at 4pm in November. Admission is £4.50 for adults and £2 for children, although a family ticket is available for £10.50. Dogs are welcome.

Visit www.kewatch.co.uk or www.castlehoward.co.uk to find out more.