Garden open season begins this weekend. From the grand surprises at Biddulph Grange to the gentle drifts of daffodils at Beverston Castle, Anna Pavord offers a guide to colourful corners to visit over Easter
Easter traditionally marks the beginning of the garden open season, the opening of the hunt-the-yellow-poster season, the start of happy wrangling between car driver and accompanying route-finder. "But you said second left." "You know perfectly well that I always mean right when I say left." Hand signals have gone out of fashion with drivers, but it's what I now resort to as navigator, poking my husband's eyes out to signal a right turn. Is this an improvement on the previous system? I fear not.

Easter is early this year, so owners of many private gardens are waiting until April before opening their gates. There are no Easter openings for the National Gardens Scheme in chilly Cambridgeshire, Cheshire or Cumbria. None in London either, but perhaps that's because everyone wants to get the hell out of the place over the Easter break.

The National Trust, though, takes Easter as the great general opening fanfare for gardens, whether it comes early or late. Later is easier, as it gives gardeners more time to clear up after the major restoration works that have to be crammed into the winter months, when paths are blocked with wheelbarrows, scaffolding poles, mountains of earth from archaeological excavations and piles of timber from the casualties of the winter storms.

When the gardens open, with paths raked, edges trimmed, lawns mown and hedges clipped, it's easy to underestimate the amount of underpinning that went on during the shut months. Biddulph Grange in Staffordshire is the site of one of the most brilliant of the Trust's transformation scenes. Each spring, the garden emerges with a new piece of its Bateman jigsaw in place. James Bateman was the extraordinary, eclectic gardener who laid out Biddulph in the mid-19th century. Around the world in 80 minutes seems to have been his idea, with visits to Egypt, China and the Himalayas included on the whistle-stop tour.

Last winter, the grand project was the replanting of the Wellingtonia avenue, a hugely ambitious last throw by Bateman, who was one of the first people to acquire seedlings of the Wellingtonia (Sequoiadendron giganteum) when it was introduced into this country in 1853. He pushed a great arm of the garden east towards the wild moorland above and planted the walk with alternating Wellingtonias and deodar cedars.

By the time the Trust took over the garden, nine years ago, most of the trees had fallen. The rest were clear-felled and the whole great avenue replanted in the original way with deodars and Wellingtonias. The embankments either side are set with new red chestnuts (Aesculus x carnea) with a backdrop of Austrian pines. It is an immense scheme, a fabulous gift to the future.

This winter's restoration scheme has been the more intimate area immediately below the windows of the house. Old photographs - in its heyday the garden was much photographed for magazines such as Gardeners' Chronicle - show a complicated series of parterres, mazes and flower-beds, known originally as Mrs Bateman's garden. It "afforded every sort of facility for lady gardening", noted the Chronicle approvingly in 1862, but by the time the Trust took over the entire scheme had disappeared.

Excavations by garden archaeologists revealed the exact placement of the original beds. One of the yews (shown in early photographs as a slender topiary cone) was still in situ, grown now into an immense tree. The beds have been reinstated and are being planted according to contemporary descriptions: red sand between the lines of box marking out the pattern, white sand round the outside of the design, China roses in the bigger beds of the parterres, cones of golden yew in the corners.

If you don't know it, Biddulph has more surprises than an episode of Twin Peaks and I'm not going to reveal them here. But like quite a lot of "episode" gardens of the 18th and 19th centuries, the surprises work best if you go round the garden in the way the owner originally intended. Buy the guidebook, which will keep you on the right track, remember to turn right by the Ape of Thoth, and keep China till last. Over tea - tea is an integral part of visiting gardens - give thanks to the head gardener Bill Malecki and his team. Nine years ago, this garden was on the brink of complete ruin. Now it's a triumph.

Gloucestershire is fertile territory for garden-visiting. More than 130 Gloucestershire gardens are listed in the current Gardens Open for Charity (NGS, pounds 3.50). I find it quite a formidable county - high, cold, rebuffing - but the creamy stone makes a wonderful backdrop for garden- makers and there are still quiet hamlets where outlying barns have not been hideously over-converted with ruched curtain blinds at every window. Good churches, too.

The church at Ashley, just north-east of Tetbury, is practically in the garden of Ashley Manor, which is open today and on Easter Monday. The wide tympanum over the church door is carved with a careful geometric design, simple and intricate at the same time. The chest tombs on the left of the church porch are covered in an exuberant tangle of white-flowering Clematis armandii and blue-flowering C macropetala. The manor has fine, clipped yew hedges and a kitchen garden.

Beverston, just west of Tetbury, is not so quiet, as it's on the main road to Dursley, but Beverston Castle is set well back from the road, approached through the old gatehouse.

The 17th-century house, a long handsome wing, butts on to the ruins of the castle which was built at various stages from the 12th to 15th centuries. A generous stone terrace, with blue scillas and grape hyacinths worming their way through the cracks in the paving stones, gives on to the old moat. The soggier bits of the moat are planted with flag irises.

An old iron footbridge over the moat connects the terrace with the rest of the garden, which sweeps down as a mossy lawn, great drifts of daffodils on either side.

This isn't a hey-hey-look-at-me garden. It's gentle, suspended, with crowds of jackdaws clacketing over the ruined towers of the old castle, and plenty of ivy under the old yew trees. In the kitchen garden are some good U-shaped redcurrant cordons trained on wires, and (big surprise) superb collections of orchids housed in two modern, lean-to glasshouses. Odontoglossums fill one house, cymbidiums the other, the pride of Robin Stevens, gardener here for the past 30 years.

The Westonbirt Arboretum, just a few miles south west of Tetbury, was started in 1829 by Robert Holford and is now owned by the Forestry Commission. It is open all year, but the grounds of the school opposite, once Holford's home, are open only three times a year, including Easter Sunday.

This is a fascinating scheme in the grand, Italian manner, with lakes and informal grounds behind the school to the right, the more formal layout to the left: wide, gravelled walks, fountains, parterres, the remains of heated walls for vines, and a fine, though crumbling, old camellia house with some of Holford's original camellias in it.

The parterres are planted out in the old- fashioned way with blocks of bedding plants - at the moment, blue pansies. Look out for the stunningly elegant iron pergola, hidden away beside an intriguing tumble of tufa. What was the tufa meant for originally? A rockery? A grotto? One day, as with Biddulph, a photograph will turn up to provide the answer.

Biddulph Grange, Biddulph, Stoke-on-Trent, Staffordshire is open Sat, Sun and Bank Holiday Mons 11am-6pm, Wed to Fri 12pm-6pm, admission pounds 4, family ticket pounds 10. Ashley Manor, near Tetbury, open today and Monday 2pm- 5pm, pounds 1.50. The garden at Beverston Castle, Beverston, near Tetbury, is open tomorrow 2pm-6pm and Easter Monday 11am-6pm, admission pounds 1.50. The Westonbirt Arboretum is open Easter Sunday 2pm-5.30pm, admission pounds 2.