What to do in the garden this weekend, by the English diarist who died 350 years ago

"Now bring your Oranges boldly out of the Conservatory, set them in the shade for a fort-night and afterwards expose them to the sun." As the nation's gardeners embark on what traditionally is one of the busiest weekends of the horticultural calendar, these words might strike a chord with those wondering if they dare risk hardening off cuttings, seedlings and precious tender plants in preparation for the floral abundance of summer.

They were written, however, some 340 years ago in The Gard'ners Almanac by John Evelyn, a 17th-century polymath best known as a contemporary of Samuel Pepys and a fellow diarist. From laying down the strategy for "hostility against Vermin" in December to bringing orange trees out of a conservatory in May, Evelyn was fascinated with the turning of the English seasons. While Pepys was chronicling the sexual iniquities and political indiscretions of Restoration London, Evelyn, the scion of a wealthy dynasty of Surrey gunpowder-makers, was dedicating his energies to the altogether more pure and gentle art of horticulture.

Armed with the religious fervour of a leading 17th-century Anglican and a fascination with man's ability to shape the landscape, this gardening philosopher set about proving to his fellow Englishmen and women his conviction that the "air and genius of gardens operate upon human spirits towards virtue and sanctity". The result was a series of pioneering textbooks on subjects that ranged from growing English oak to the painting of flowers. They made Evelyn one of Britain's first authorities on the cultivation of plants.

But while his diaries and letters on subjects from the execution of Charles I to the Great Fire of London have been favourably compared to Pepys himself, Evelyn's role as originator of Britain's first "how to" guides on gardening has often gone unrecognised. Now, on the third centenary of his death on 27 February 1706, there are calls for greater recognition of his works, including the Kalendarium Hortense or The Gard'ners Almanac - one of the first works in the English language to give a chronology of what to do and when in the garden.

Evelyn's Elysium Britannicum, an attempt to produce an encyclopedia on gardening which was begun in the 1650s and remained unfinished at the time of his death, was recently republished after being transcribed by an American academic. Evelyn read extracts of the work to Pepys, who described it as a "discourse that he hath been many years and now is about, about Guardenage; which will be a most noble and pleasant piece".

A conference will be held in a fortnight at Wotton House in Surrey, the ancestral home of the Evelyn family, to highlight John Evelyn's role in shaping Britain's green space and his foresight on issues including diet and the environment. From an early treatise on the merits of vegetarianism to a closely argued text on the importance of trees, experts point out that his advice was in many ways ahead of its time.

One delegate at the conference will be Frances Harris, head of modern historical manuscripts at the British Library, which holds the largest archive of Evelyn's works. She said: "He had a very powerful sense of the spiritual nature of gardening. His reference was the Garden of Eden and having spent a long time travelling in Europe, he realised England was a long way behind the Continent in knowledge and skill.

"His great act of creativity was his work on gardening. He had a deep-seated anxiety that natural resources were being over-exploited. He was an early environmentalist in many ways."

Above all, Evelyn, an avowed Royalist who fled to Paris during Oliver Cromwell's rule, endeavoured to apply science to his horticultural labours. When exhorting his compatriots not to destroy woodland in favour of creating pasture - a practice which could be likened to the destruction of the Amazonian rainforest - Evelyn wrote: "Tis a thing to be deplor'd, that some persons bestow more in grubbing up and dressing a few Acres which has been excellent wood, to convert it into wretched pasture, not worth a quarter of what the Trees would have yielded, well order'd and left standing."

He turned his home, Sayes Court, on the edge of the Royal Dockyards in Deptford (an unglamorous suburb even in 17th-century London), into a giant open-air testing ground for his theories. Working under the subtitle of "Directing monthly what he is to do monthly throughout the year and what fruits and flowers are in prime", his Kalendarium Hortense then transformed his findings into a sumptuous book, complete with engravings of toiling plantsmen and lolling aristocrats.

Written in the 1660s, it is complete with money-saving tips and advice. It tells you when to feed the apple trees with a good dollop of manure, and how to protect what we might now call water features - the pipes to the fountains of England's stately homes - with "warm litter out of the stable" so that the frost wouldn't crack them. "Remember it in time and the Advice will save you both trouble and charge," urges Evelyn. Alan Titchmarsh, eat your heart out.

His chapter on bee-keeping in May, a sign of the importance of honey to cuisine in the late 1600s in the absence of sugar, was diligently followed for decades.

The book, which was initially published as an appendix to Sylva, a famous treatise by Evelyn on the growing of trees written to boost timber production for the Royal Navy, also set out the procedures for growing a wide range of fruit and vegetables, including the celery-like plant called Alexanders (Smyrnium olusatrum, or horse parsley, now regarded as a weed).

But while Evelyn, a founding member of the Royal Society, grandly professed that the Kalendarium was "a specimen of our Affection to the Publick", it seems that the self-styled Renaissance Man of English gardens was less populist than his exhortations about winter pears and manure indicate. Writing in the London Review of Books, Keith Thomas, a fellow of All Souls College, Oxford, explained: "[Evelyn] is not writing for suburban gardeners, whose 'cockney plantations' with their 'starch't and affected designes' he despises as smelling 'more of paint then of flowers'.

"Nor does he address mere 'cabbage-planters', who garden in order to subsist. His intended audience is the 'best refined of our nation', 'princes, noblemen and greate persons', who can afford to maintain a garden on an appropriately magnificent scale, and whose concerns will be aesthetic rather than utilitarian."

Indeed, Evelyn describes the perfect garden in Elysium Britannicum as being 70 acres, surrounded by a 13ft brick or stone wall and tended by an army of gardeners, craftsmen and labourers. It should contain (among other costly items), canals, grottoes, music (described as "an absolute necessity") and hydraulic gizmos such as talking statues.

If such requirements were not sufficiently challenging, then the master gardener's specifications for a garden lawn roller would have tested even his extravagant monarch, Charles II - it was to be fashioned from marble columns from Smyrna.

Others have suggested that the talents of Evelyn, who lived to 86, lay as much in assimilating the achievements of other pioneering gardeners as producing his own original research. His expertise on trees, which won him brownie points for restoring timber production to levels that would help ensure Britain's maritime dominance, has been largely attributed by some scholars to unashamed borrowing from Dutch horticulturalists.

Brent Elliott, librarian for the Royal Horticultural Society, said: "Evelyn was a very influential gardener of his era and he certainly helped make information available to an audience in England that it would not have seen before. But he benefited by coming after the Commonwealth, [during which time] the country was isolated, and imparting knowledge from his foreign travels. There are some who have argued that what he was in fact good at was reproducing the work of others."

Sadly, much of the evidence that might attest to Evelyn's originality has been lost. Sayes Court, where he spent 30 years applying his horticultural philosophy, has long since disappeared and all that remains is an incomplete plan from the 1650s.

Similarly, the final volume of Elysium Britannicum, which contained what experts believe was some of his most esoteric work, including chapters on how to create a gardener's laboratory and the painting of flowers, has been lost. Perhaps, in the search for some kind of testimony, we should look at the philosophy that underpinned his month-by-month advice. Gardens are, he wrote, "of all terrestiall enjoyments the most resembling Heaven, and the best representation of our lost felicitie".