I am working at home, gazing from my office window at eight tall agapanthus in full flower, swaying in the light breeze, glowing blue and white in the intermittent sunshine. Behind them a clump of fragrant sweet peas, in shades of pink and mauve, are ready for the umpteenth picking of the summer.
Still farther away the hydrangeas are only just past their peak and the apples on our ancient tree are swelling perceptibly day by day, some falling on the narrow lawn – which, I notice, needs yet another cut. Earlier, a fox was strutting snootily on top of the brick wall that separates my plot from my neighbour's, but he seems to have returned to his lair in the back alley for a midday snooze.
The garden would win no prizes at Chelsea; but it is our own, lovingly – if sometimes neglectfully – nurtured by my wife and me for more years than we care to remember. ("I love the unkempt look," enthused David Sandison, when he came to take the picture. I don't think it was unkindly meant, although we prefer "naturalistic".)
Even if we lack advanced horticultural skills, we are happy to be among the great majority of British householders whose life is enhanced by the open space, however tiny, outside the kitchen door. The bad news, according to a Government report last month, is that we are slowly becoming a threatened species.
As population pressures increase, new homes are being built without their own gardens – not just flats but also town houses, squeezed in cheek by jowl to make the most efficient use of limited space. Worse, some existing, flourishing gardens are being sacrificed to developers in the practice known as garden grabbing.
Already more than 2,000,000 homes have no access to a garden. According to official estimates, that number will increase remorselessly over the next decade, reaching 2.6 million by 2020. It is a gradual process – attrition rather than sudden devastation – but, unless it is stemmed, fewer and fewer householders will enjoy that precious green hinterland. The rest will have to make do, if they are lucky, with a narrow balcony just big enough for a couple of pots of geraniums.
Some of these deprived citizens might have access to communal garden areas, where they can sit in the sun or exercise the dogs and children. These fulfil one basic function of a garden – fresh air – but do nothing to satisfy our all-important need for a personal creative outlet, where we can exert our limited control over nature to produce something expressing the unique taste and sensibility that confirms our individuality.
"Then let them get allotments," as Marie Antoinette might have put it. Except the waiting lists for such blessed plots are now so long that many of today's applicants could be dead or incapacitated before they rise to the top.
In recent years, voices have been raised against this gradual loss of gardens, but to no avail. In 2007 Greg Clark, MP for Tunbridge Wells and the Conservatives' spokesman on energy and climate change, introduced a Private Members' Bill that would have altered the status of private gardens from brownfield sites to greenfield sites, meaning that they could not be built over without special permission. This would not have brought garden grabbing to a complete halt, but it would have made it more difficult.
The Government refused to throw its weight behind the Bill, so it did not become law. Last year Conservative peers tried to resuscitate the measure, but that failed as well. The Royal Horticultural Society and Garden Organic, the charity that promotes chemical-free gardening, have long been calling for tougher controls on the garden grabbers, as have high-profile environmentalists such as Zac Goldsmith.
The huge importance we place on possessing our own territory, where we are monarchs of all we survey, can provoke extreme and irrational behaviour. From time to time the newspapers report court cases involving implacable neighbours arguing with increasing fervour over who is the rightful owner of sometimes only a few feet of marginal land between their properties.
Then there are those who insist on keeping themselves to themselves by planting hedges of leylandii, the notoriously fast-growing conifer, placing their neighbours in permanent shadow. The rows become testy and querulous, until finally patience snaps and the aggrieved party brings in the lawyers.
The concept that every household has a right to its own self-contained garden is not part of our ancient privileges – so far as I know, there is no mention of it in Magna Carta. In the Middle Ages the only gardens worthy of the name were attached to monasteries. If peasants had a stretch of land next to their cottages, they would use it for growing vegetables and fruit, not flowers.
When the monasteries were dissolved in the 1530s, their lands were distributed among Henry VIII's cronies, many of whom continued to cultivate the gardens. Soon, no stately home was thought worthy of the name without its accompanying rolling acres, usually incorporating a kitchen garden and formal flowerbeds.
By the end of the 16th century, gardening was well-enough established in the national psyche for Shakespeare to make numerous allusions to it in his plays. More than once he used the metaphor of a garden choked with weeds to symbolise a nation rotten to the core.
Every gardener's favourite Shakespearean scene comes in Richard II, where the Queen, strolling among "dangling apricocks", learns from the gardener that her husband has been captured. In her despair she rounds on the messenger, uttering the most terrible curse she can devise for a gardener: "For telling me this news of woe, I would the plants thou graft'st may never grow."
For nearly two centuries, gardening remained largely the preserve of the monied class, who employed teams of toilers to keep everything spick and span. But with rising prosperity, the burgeoning middle class of shopkeepers and clerks built homes on more modest plots of land, creating gardens small enough to cultivate themselves.
In 1722 Thomas Fairchild, a pioneering London nurseryman, wrote a book called The City Gardener, in which he declared: "One may guess at the general love my fellow citizens have for gardening, in the midst of their toil and labour, by observing how much use they make of every favourable glance of the sun to come abroad [out of doors] and of their furnishing their rooms or chambers with basins of flowers ... rather than not have something of a garden before them."
In the following century, the rapid increase in population, especially in the cities, led to the introduction of the semi-detached house with a small garden at the front (many now transformed into parking spaces) and a larger one at the back. Very soon came terraces with back gardens the same width as the houses themselves. It was then that gardening became the hobby of choice – indeed of necessity – for millions of householders.
They bought manuals to tell them what to do and when to do it. They devoured the works of such green gurus as William Robinson and Gertrude Jekyll. And when, through the medium of the Underground and suburban railways, London spread to such faraway places as Golders Green, Pinner and John Betjeman's Metroland, the posters designed to lure people to settle there stressed the rustic aspects of suburban life, especially the ample provision of gardens.
Some years ago I wrote a series of articles for The Independent on Sunday magazine about unusual gardens. They came in all sorts and sizes, reflecting the obsessions of their creators and custodians. One man was growing bananas in a tiny garden in Hackney, carefully wrapping them in a fibrous material so they would survive the winter. A Nottingham woman had planned her flowerbeds around a host of unusual ornaments picked up from scrap dealers – gnomes and much else. A young woman had designed what she felt was a suitable space for Oriental-style contemplation in Balham, south London. Another specialised in bizarre topiary. An aspiring actress had taken over the roof of a block of Victorian charity flats in Pimlico and created a wispy wonderland of overflowing pots and containers.
When I asked them what drove them to such excesses, they nearly all gave the same answer, if in different words: "It's the only place I can really express myself ... It's just me and no one else ... It's my own little kingdom: nobody tells me what to do in it."
The most remarkable of the gardens I visited was that created and cherished by Derek Jarman, the late film-maker, outside his house on the pebbles of Dungeness, just yards from the sea. He found plants, such as sea lavender, that relish the daunting conditions, and he interspersed them with powerful statues and stone formations. It was the ultimate expression of how a garden reflects the passions of the person who makes it.
"Paradise haunts gardens," Jarman wrote, not long before he died, "and some gardens are paradises. Mine is one of them. Others are like bad children – spoilt by their parents, over-watered and covered with noxious chemicals."
To discover just now much emotion gardeners invest in their plots, you have only to visit some of the 3,600 private gardens open for charity every year under the National Gardens Scheme and listed in The Yellow Book, a perennial bestseller. They range from large formal appendages to stately homes and country mansions, to cosy spaces behind run-of-the-mill houses.
At this time of year, scores of them are open at weekends in all parts of the country. Increasingly, owners of small gardens in villages are getting together with their neighbours to open on the same day, so that for the price of a single ticket visitors can see half a dozen or more variations on the pastoral theme. The most ambitious of such co-operative events takes place annually at Walsham le Willows in Suffolk, where later this month, on the Bank Holiday weekend, 30 gardens will be open for inspection.
These are quintessentially British occasions. Tea is served, along with home-made cakes and jam. Many of the garden owners take cuttings from their favourite plants and sell them in pots, carefully labelled. Seek out these ace cultivators and they will talk you through their triumphs and disasters, sharing their problems with the weather and pesky pests, describing how they overcame them to produce a passable display. They are not actively seeking your praise or sympathy but are grateful when you offer it, as fellow-participants in the annual battle with the elements.
Prince Charles is among devoted owners who open their gardens to the public, although you can visit Highgrove only as part of a pre-arranged group, not individually. I was there in June, on a golden Gloucestershire day during that window of optimism before we came to grasp that the warm, dry summer promised us by the forecasters was not going to materialise.
Like any other private garden, Highgrove reveals much about the owner's enthusiasms and lifestyle. Although there are some formal borders, much of the garden is given over to wild flowers to encourage visits from birds and other living creatures. It is, too, dotted with sculptures and man-made decorative features, some of which Prince Charles has commissioned and others that have been given to him on his global travels. One courtyard is decorated with busts of the prince himself at various stages of his life.
It is fair to say that the heir to the throne is at least as well known for his zeal as a gardener as for any of his other achievements, at least in this country. He has by any standards led an eventful life – the divorce, the scandals, the tragedy of Diana's death and the eventual marriage to Camilla – yet if you ask people what they know best about him, many will respond that he talks to his plants. The legend stems from a remark he made – a joke, really – during a television interview at Highgrove as long ago as 1986. "I just come and talk to the plants ... They respond, I find."
To describe gardening as a characteristically British obsession may fail to do justice to keen trowel-wielders from other parts of Europe and from America, several of whom I count among my friends. Yet in none of these places is horticulture ingrained so deeply into the national character – partly, no doubt, because they have a longer tradition of living in apartments many storeys above the nearest access to the outdoors.
It is no accident that those Americans whose homes do come with adjacent space habitually describe it as their yard, not their garden. The implication is that the practical functions of the area – the barbecues, the basketball net, the children's swings – mean more to them than the cultivation of flowers and vegetables. The American garden writer Charles Elliott conceded British supremacy in this regard when he described our country as "the world's greatest potting shed".
Back at my office window, I broaden my field of vision to take in my neighbours' gardens, displaying a wide variety of possible treatments. To my left all is orderly, the very opposite of unkempt. Near the house is a paved area for the barbecue, the chairs, the table and the parasol: they eat and entertain outside a lot more than we do, with discreet wind chimes enhancing the idyll. Further back are neat and well-tended flower borders, and a trio of raised beds for vegetables.
The people on the other side have a young family, so they installed a small swing and slide at the end of the garden and a washing line for drying the toddlers' clothes. Nothing very decorative there – yet in the early spring their magnolia is quite spectacular. And further along the terrace a couple of professional designers have installed soft lights to help us appreciate their highly distinctive vision at all hours.
In 1935, at the height of an earlier recession, the plant hunter Frank Kingdon Ward wrote: "Even in these hard times, let us not neglect our gardens, but rather sacrifice much else, that we may enjoy the purest and most exquisite pleasure in life: the yield of mother earth in all its strange forms. Truly the cultivation of flowers is something more than a luxury; it is a religion."
The threat to this green-fingered heritage is not an immediate one. The figures show that the disappearance of private gardens is a slow, insidious process. Yet gardeners know that the time to tackle disease is at the very first sign that a plant is ailing, while there is still a good chance of saving it.
That is why we need to act now to halt the drift from our own cherished patches to communal spaces that are all too often adorned in ways that are bland, low-maintenance, unimaginative and studiedly inoffensive – all things to all people. We need our private paradise. We must nurture the British garden, embracing as it does a rich range of human emotions – from love, joy, hope and ambition to gloom, frustration and dreadful disappointment. Like life itself, really.
Michael Leapman's latest book, "The Biggest Beetroot in the World", was published last year by Aurum Press. He is the author of "The Ingenious Mr Fairchild: Forgotten Father of the Flower Garden"
Britain in bloom: The best public gardens to visit
The Lost Gardens of Heligan
The discovery of the gardens at Heligan in 1990 by Tim Smit led to a restoration project to bring the estate back to its glory. In its second decade, Heligan is still evolving. The Jungle is a year-round treat, with a range of exotic plants from Victorian plant hunters. With wildlife webcams, watch close-up pictures of the native wildlife.
St Austell, Cornwall
Open 10am-6pm daily
£5 children; £23.50 family ticket
The Rolls Royce of botanical gardens. As part of its 250 anniversary celebrations, visitors are encouraged to learn about the important role botanical gardens can play in the preserving the environment. Particularly spectacular this summer is the Waterlily House – witness the Amazonian water lily, Victoria amazonica, almost 2.5m in diameter. The tree top walk is well worth a visit.
Open 9.30am-5.30pm daily
£13 adults; children free
The Royal Horticultural Society has been cultivating its flagship garden at Wisley for 100 years as a platform for research. August is full of activity for the school holidays and children go free for the month. This summer's Maize Maze is centred around a pirate ship, with tropical plants and flowers mixed with banana plants. For grown ups there's the tropical greenhouses, mixed borders and September's annual flower show.
Open Mon-Fri 10am-6pm; Sat-Sun 9am-6pm
£8.50 adults; £2 children or free in August
Sissinghurst Castle Garden
Built around the ruins of an Elizabethan mansion house, Vita Sackville West's Sissinghurst estate is deservedly one of Britain's most celebrated gardens. The walled ruins inspired West's husband, Harold Nicholson, to create a series of intimate gardens each divided by colour or theme. Most impressive is the white garden, which boasts a remarkable collection of white flora. Enjoy a taste of Sissinghurst with home-grown organic vegetables in the restaurant.
nationaltrust.org.uk Open 11am-6.30pm, closed Weds-Thurs.
£9.80 adults, £4.90 children, £24.50 family ticket
As well as being one of Britain's finest historic houses, not to mention the setting for Jeremy Irons' "Brideshead Revisited", Castle Howard houses 1,000 acres of gardens. The ancient woods are a rare botanical treat with the one of the most extensive plant collections in Europe. The newly-planted ornamental vegetable garden is in full swing – pick up some of the produce in the farm shop.
York, North Yorkshire
Open 10am-6.30pm daily
£8.50 adults; £6 children; £23 family ticket
In 1959, Lady Anne Berry met plantsman Collingwood Ingram, who gave her a few plants. Over 30 years, she developed Rosemoor into an exotic paradise, bringing back species from across the globe. The RHS have preserved her gardens, as well as developing the rest of the estate into 65 acres of gardens and woodlands. Lady Anne's red and orange tropical borders are unmissable this month.
Great Torrington, Devon
Open 10am-6pm daily
£6.50 adults; £2 children
National Botanical Garden of Wales
The National Botanical Garden is a remarkable achievement in a mere nine years. The Welsh rare plant collection is unique, while the rock garden tells the story of Welsh geology. Evening primroses and red hot pokers dominate the Mediterranean Garden in August, while the Great Glasshouse is full of fragrance.
Open 10am-6pm daily
£8 adults; £4 children; £19.50 family ticket
High on Hampstead Heath, Kenwood House is a welcome retreat for many a Londoner. The surrounding parkland was influenced by the English land- scape gardener, Humphry Repton, who envisaged a circuit walk with a series of contrasting landscapes. The Ivy Arch frames impressive views over the lakes and the butterfly garden is beautiful in late summer. Alternatively, there is no better place for an early-autumn stroll than Hampstead Heath.
Open 11.30am-4pm daily
Free, donations welcome
Since Gerald Loder began to introduce exotic trees and shrubs to the estate in 1903, Wakehurst has been at the forefront of plant conservation. It's home to the Millennium Seed Bank, the world's largest seed conservation project – aiming to collect 24,000 species. Out in the grounds, the Southern Hemisphere Garden is glorious in August – bursting with hypericums and skimmias, and don't miss the stunning Sir Henry Price cottage garden.
Ardingly, West Sussex
Open 10am-6pm daily
£10, under 16s free
Glasgow Botanic Gardens
The Victorian glasshouses at Glasgow Botanic Gardens are probably the most impressive you will ever see. Kibble Palace is a luxurious centrepiece, where marble statues sit alongside the national collection of Australasian tree ferns. Eleven glasshouses contain tropical plants, including a collection of tropical orchids. Guided tours by arrangement.
Open 10am-6pm daily