It's a vast theme and she handles it well, showing how ideas - on garden- making as well as science and philosophy - moved over boundaries. It's a book about design rather than plants, essential reading for anyone heading this summer towards Italian gardens such as Villa d'Este - or to less well-known gardens such as Queluz, hidden away between Lisbon and Sintra. Ms Woods thinks it the greatest Rococo garden in Europe. I want to go there now. Started in 1746 by the Infante Dom Pedro III and decorated with more than 200 lead statues from John Cheere's workshop at Hyde Park Corner, it is a dreamy garden, its central canal lined with fabulous ceramic tiles.
The book is cleverly organised into chunks that are neither too big to digest nor too small to make you feel cheated of detail. The structure is chronological, moving from medieval gardens and the Renaissance to the wonderfully mad menageries, obelisks and ornamental dog kennels of the Rococo garden. "Every hovel for cows has bells hanging at the corners," wrote Disgusted of Tunbridge Wells to The World in March 1753.
Ms Woods highlights the great Renaissance contribution to garden design: the unity of structural elements in a garden. She shows how, by choosing a gardener and engineer to advise him, not an architect, Charles VIII's French gardens never achieved the cohesion of their Italian counterparts. But what Charles lost on the vistas, he gained on the fountains. His hydraulics man, Fra Giocondo, was the best in Europe.
Classical Italy is a lost continent to most of us, but its history and heroes were familiar territory to the educated garden-makers who inhabit the 350 years of May Woods's survey. The gardens they made were rich in symbolism and classical allusion, illuminated in this elegantly designed and illustrated book.
Easter traditionally marks the opening of the garden visiting season and your licence fee is pounds 3.50, the cost of the new edition of the Yellow Book: Gardens of England and Wales Open for Charity. It lists 3,500 gardens, grand multi-acred mansions, small groups of terraced houses, roof gardens, water gardens and vegetable gardens (my favourite). In London alone, there are 29 new gardens opening for the first time, including the Chumleigh communal garden in Southwark, where you can see gardening in Oriental, African, Islamic and Caribbean styles.
Because the ratio of available weekends compared with gardens to visit is so unbalanced, you also need The Good Gardens Guide 1997, edited by Peter King (Ebury Press, pounds 14.99). This is by far the best of the available guides, covering 1,000 of the best gardens in Britain and a few in Europe that are no more than a Shuttle-hop away. It caused a pleasant uproar when it first came out eight years ago because it graded gardens like restaurants and awarded stars to the best. A hundred gardens have the highest two-star rating, including Chatsworth (a thrilling garden at any time of the year) and Ard na Mona, County Donegal. For those who want to make a full weekend of it, there is a useful section on hotels with good gardens.
A lack of classical education may hinder our understanding of 18th-century gardens. It also makes us splutter over Latinised plant names. But the names are much easier to remember if you have some inkling what they mean. That is why I love Stearn's Dictionary of Plant Names (Cassell, pounds 14.99). Now 86, the brilliantly erudite Professor William Stearn was an authority even by 1930 when he contributed to a session of the Nomenclature Section at the International Botanical Congress.
If, for instance, you have ever wondered about the meaning of meleagris (as in Fritillaria meleagris), look no further. It means "spotted like the guineafowl". How exact. Forsythia, blooming now in a million spring gardens, is named after William Forsyth (1737-1804), the Scottish superintendent of the gardens at Kensington Palace. He invented a "plaister", a mixture of lime, dung, wood ashes, soapsuds and urine, for which he made extravagant, and very dubious claims. I've never much liked forsythia. I like it much more now because of the knaveish Forsyth.