An English garden can become a delight in the spring. Perhaps that's why visitors adore looking at them, deriving boundless satisfaction and sometimes even pangs of envy. Two Thames Valley gardens illustrate that point.

Shape is everything at Cliveden, operated by the British National Trust - 200 acres rolling across a series of gentle undulations overlooking the Thames just upstream from Maidenhead.

Started by the second Duke of Buckingham in the late 17th century and gradually improved upon by successive owners and the landscape artists they employed, it is a marvelous place to explore at leisure, taking a picnic and spending a whole day there to appreciate its enormous variety.

From the terrace in front of the house you look down on a beautiful balustrade of marble and Roman brickwork bought from the Villa Borghese in Rome (which now has to make do with a copy) and across it to the serene formal parterre, its geometrically-shaped beds, and the lazy river beyond.

Innumerable walks radiate away from here to glades and small self-contained gardens, some with vistas of the river, others with temples and statues and pools, wild and bosky bits and hidden formal areas: a never-ending delight.

Quite different in scope and concept, but quite magical in effect, are the gardens of Pusey House, between Abingdon and Harringdon. This is entirely the creation of Mr. and Mrs. Michael Hornby, who bought the 18th-century house and grounds just before World War II, and it reflects a relationship between people and plants that is uniquely English.

Mrs. Hornby, who is also a distinguished flower-painter, knows every growing thing in her garden by name, and as I walked round with her I felt they knew her, too, and that winter's few casualties must have expired with real regret.

I had been there, years ago, in summer, when the fantastic herbaceous border along the kitchen-garden wall was in full bloom and my children, then quite tiny, caught their breath at the sight, half expecting Mr. McGregor and the flopsy bunnies to materialize from round a corner.

This is a garden to gladden the heart, of course, wandering down to the lake and across the "Chinese" bridge, mentally congratulating the two black swans who seem to have made a new home here, looking into the miniature church, the temple and the walled Lady Emily's garden. But it is also a garden from which to learn while clutching the guidebook with its lists of Latin names and making copious notes.

Both these gardens, and many more, are pinpointed on a useful little leaflet produced by the Thames and Chilterns Tourist Board. The English Tourist Board also has produced a new booklet on the subject, "Visit an English Garden," which can be purchased by writing the board at 4 Grosvenor Gardens, London SW1W UDU. And there is also the traditional "Gardens of England and Wales," available from the National Gardens Scheme, 57 Lower Belgrave Street, London SW1W ULK.