On the way to work tomorrow, as you hurry, head bowed, to the crowded bus-stop or station, or pause in the car at the red traffic light, feeling your blood pressure start to mount as you see that, on the other side of the junction, the traffic still isn't moving, do yourself a massive favour: look up.

What may swim into your line of sight is greenery. We've been without it for five months, do you realise? And now it's back. Those things called trees, those tall roadside posts that for the whole winter long you haven't glanced at, that have seemed no more than dark straggly alternative streetlamps without the lighting, have suddenly in the past 10 days sprouted life, and now, this week, are at their most intense.

For example, look at the horse chestnuts, the conker trees beloved of schoolboys, if you live in an area lucky enough to have them. Go on, look. Once you do, you'd have to have a soul made of concrete not be stirred, for right now, at least in southern Britain, the buds have just burst and the leaves have poured forth and they are of a quite spectacular colour. It's green, of course, but it's a special green, it is more than emerald, it is iridescent, as if the leaves were fresh-painted, as if they were glowing from the inside; and in the next few days they will be joined by giant upright white blossoms, big as a bunch of bananas, commonly known as Roman candles. The whole thing then looks like a living firework display, and it's free, and no streetlamp ever looked like this.

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It's not just the horse chestnuts; cherry blossom and apple blossom is out now in gardens, as are the lilacs, and in hawthorn hedges there is a green mist of leaf wrapped around the branches. Greenery is bursting out everywhere on the trees in our towns and cities and suburbs, so much so that if you do look up from the slog to work and catch a glimpse of it, your soul will lift; and at last, at long, long last, someone has put a value on it.

It has a boring name (Capital Asset Value for Amenity Trees) and an acronym (CAVAT), but don't let that put you off; it's the thought that counts. Developed by the London Tree Officers' Association ( LTOA), the professional body for tree specialists working for the London boroughs, this is a system that, for the first time, assesses a tree's worth, according to its size, health, historical significance and how many people live near to enjoy it. It assesses worth in actual money terms; that's the point, in this age that worships cash enough to make heroes of hedge-fund managers.

The results, which were released this week, are surprising: most ordinary street trees that you might not give a second glance to (especially hurrying to work) turn out to be worth between £8,000 and £12,000, but for more special trees in more special places, even in the London suburbs, the values start to soar: an oak in Southgate, North London, for example, has been valued at £267,000 and a plane in Epping High Street at £200,000. At the top of the list, in Mayfair's Berkeley Square, yes, that urban oasis where the nightingale was meant to have sung (take it from me – it was a robin) there is a venerable plane tree on which the lads from the LTOA have stuck a value of £750,000. It has been there since Victorian times, but all the same – whew! you whistle – that's a lot of money for a trunk and some branches. There are dozens of others now valued at more than £500,000, too, in leafy and affluent boroughs such as Westminster, and Kensington and Chelsea.

The figures give people pause, they make them stop; and that's the point, that's why the system is needed, for in recent years, local authorities have been chopping down urban trees at such a rate of knots that the phrase "chainsaw massacre" has been applied to the process.

Behind it lurk those much criticised developments of the last quarter-century, the compensation culture, and the health-and-safety culture. There is no doubt that a big tree growing too near a building can, if it has a major root system, ultimately cause the building problems. It can become entangled in the foundations, and its thirst for water also leads to moisture being sucked from the ground, causing soil shrinkage and sinking buildings. (A mature deciduous growth can draw 50,000 litres of water a year from surrounding soil). Furthermore, there is no doubt that if a big old branch snaps off a big old tree it could hurt somebody.

Yet there is growing evidence that healthy mature trees are being felled by risk-averse insurers and councils because of the mere suspicion that they may affect neighbouring properties with subsidence, or fall on people.

In the past five years, London councils alone have chopped down almost 40,000 street trees, including some more than 100 years old. Some were aged, diseased or dying, but 40 per cent were removed because of insurance claims; yet a report commissioned by the London Assembly said that only 1 per cent of tree-removals were justified.

The picture is repeated nationwide, and was illustrated vividly in February in a report to the Department for Communities and Local Government, Trees in Towns II, which was the largest-ever survey of urban trees in England, covering streets, parks, schools, churchyards, allotments and private gardens in 147 towns and cities.

It found that, despite the key role they play in combating climate change, and creating pleasant environments (the report's own words), Britain's urban trees are under threat. Only 11 per cent of trees in towns are now between 50 and 100 years old, the survey discovered; only two per cent are more than 100 years old. That means: when they get big, they get chopped down. When the report was published, the Government put a gloss on it – "er, much has been done, but much remains to be done," and so on – but the Opposition got nearer the point.

Eric Pickles, the Shadow Communities and Local Government Secretary, warned that the leafy character of urban areas was under threat. "Whitehall's failure to tackle the compensation culture and the heavy-handed application of health and safety regulation is doing more harm than good," he said. "Trees have a vital role to play in tackling climate change and improving quality of life, yet Britain's leafy suburbs face a chainsaw massacre under Labour."

Tasty soundbite, eh? You can almost hear Mr Pickles's lips smacking as he uttered it. But even making substantial allowances for political point-scoring, it does seem likely that far, far too many urban trees are now coming down. The London Tree Officers' Association chairman, Andy Tipping, said that, too often, insurance companies facing a claim for subsidence were demanding that trees be destroyed, and councils were too willing to cave in to their demands.

The new CAVAT system his association has drawn up will change things, he hopes, because in future the high value of trees – in London alone the total value of them is now estimated at £6.4bn – will demand extra engineering work by insurers to prove a link between a tree and subsidence, not least because various other causes, from broken drains to drought, can be behind buildings getting that wonky look. The higher the tree's value, the more proof insurers will need that it is really causing problems before they can chop it down. It is planned to roll the system out nationwide next year.

"Often an insurer will point the finger at the tree, it is chopped down and then subsidence problems in a house persist," said Tipping, a tree officer in Barnet, north London. "Companies pay out vast sums repairing buildings and then, some months later, new cracks appear. Under the new scheme, there will be more on-site investigations to find the source of damage at the beginning of a claim."

He said that in one case he was asked to remove a 130-year-old oak that was three houses away from a property with subsidence, and there were no roots near to it. "It's an absurd situation," he said. "People still don't understand that subsidence is a problem of buildings, not trees. In many cases, trees are not the main culprit. It's other reasons instead such as Victorian drains, poorly installed double-glazing, or climate change."

The other reason for not removing them, of course, is that people love trees. Research published yesterday suggests that almost 10 million people intend to plant a tree in their garden this year. (Won't that get the insurers worried?) When trees are cut down in towns and cities, nearly always by some overweening authoritarian body, like a council, or a railway company, local people often protest vigorously: they suddenly realise they are actually very fond of what they had always taken for granted.

Why do we love trees? We can think of many practical reasons – the wood, the shade, the shelter, the apples, the pears – but there are deeper reasons too. Beauty is obviously one. The horse chestnuts in young leaf this week are so striking that they pull you up short, as are the blossoming cherries, reminding us of the opening of AE Housman's famous lyric: "Loveliest of trees, the cherry, now/ Is hung with bloom along the bough/ And stands about the woodland ride/ Wearing white for Eastertide."

It isn't only trees in spring blossom that move us; trees in autumn colours are another still-life firework display; indeed, the basis of a whole tourist industry in New England, where the hordes of visitors who come to look at the fall foliage are known as "leaf peepers". Even trees in high summer, the least interesting part of the period in leaf, can provide a spectacle, such as the beeches of the woodlands of the Chilterns, whose tall, straight trunks, combined with the light falling between them, give the appearance of leafy cathedrals.

Yet perhaps there is something even beyond beauty in our attachment to the oak and the ash, the lime and the hornbeam, the yew and the Scots pine. In the last 20 years the new discipline of evolutionary psychology has made many suggestive interpretations of the origins of human feeling, taking them back to our distant ancestors; the rationale is that we have been office workers for four generations, and we were farmers for about 400 generations; but before farming, we were hunter-gatherers for 20,000 generations or more, and much of our genetic make up must have been constructed then.

There's no proof of this, of course; there can only be suggestions, but they are powerful ones (why do all children like to hide? Because the children who didn't hide, when the predators or the attackers came, didn't survive to pass on their genes). Is there perhaps something in us that goes far, far back, to account for our love of trees, something more than beauty or utility? Some deeper attachment formed during the aeons when we lived in the forest?

It's fanciful, of course it is, especially now most of us only have the street, the house, or the block of flats; and we can never know. But we do know that when the trees that grace our street, our road, our courtyard, are threatened with toppling, we do not like it one bit. At least now there is a system, thanks to the London Tree Officers' Association – that gives tree-lovers a chance to fight back when the insurance company or the council sends someone with a chainsaw.

THE BEST NATIVE TREES TO PLANT YOURSELF

Ash (Fraxinus excelsior)

Fairly abundant across Britain, the ash is a native deciduous species known for its elegant grey bark and distinctive black buds, which are often the last to open in spring. A large tree, it can live up to 200 years and reach a height of 45 metres. Characterised by having delicate "leaflets", rather than undivided "simple" leaves, the ash can be male, female or both and produces purple catkin female flowers that ripen after fertilisation into seeds or "keys". Given the room to grow and spread, the ash has a striking silhouette, although its lack of low branches has traditionally made it unpopular with gardeners. The tree does best in fairly moist but well-drained fertile soils with a pH above 5.5. Its strong, hard timber is a natural shock absorber and can take a hard blow without splintering, so has been used to make hockey sticks, oars, paddles, billiard cues, cricket stumps, polo sticks and, until metal ones came along, truncheons. JAMIE MERRILL

Goat Willow (Salix caprea)

The name is thought to come from the first known illustration of the species in Hieronymus Bock's 16th-century Herbal, where the tree is shown being eaten by a goat. Also commonly known as a pussy willow, its buds, or catkins, bloom in March and April before the leaves appear. It grows to 6-12m and is native to Europe and western and central Asia. Russian Orthodox, Polish and Bavarian Roman Catholics carry sprays of goat willow on Palm Sunday. The wood is brittle, so doesn't produce useful timber but the bark contains tannin, used for tanning leather, and salicin, used to make aspirin. Goat willows usually grow in woods and hedgerows, where they provide a feeding ground for moths, but the species is also a pioneer plant found in clearings and wasteland. REBECCA ARMSTRONG

Hazel (Crataegus monogyna)

A member of the rose family, the hawthorn is densely leaved and thorny with a short trunk. Some might classify it as a shrub but in the wild, it is described as a small tree. While not the tallest example of either, the hawthorn is known for its longevity and can live up to 250 years. The hawthorn produces fragrant white flowers in late spring, followed by glossy dark red fruit in November. Known as "haws", the fruit can be harvested to make haw jelly and is as an important source of food for voles, wood mice and birds. Its thorny stems make it an ideal boundary tree. It needs to be pruned twice a year, in summer and autumn, and regular weeding at its base will improve its growth significantly. JM

Hawthorn (Corylus avellana)

Loved for its tasty nuts, the hazel is native to almost all of Europe. It's no giant, growing to 6m, but it is hardy. In their natural state, hazels can live for 60 years, but coppicing them, which involves cutting the tree back to ground level to encourage new growth, can result in a lifespan of up to 600 years. Hazelnuts are important for the survival of the dormouse, but their popularity with squirrels means trees are stripped of their nuts before they ripen. A hazel rod is best for water divining. RA

Silver Birch (Betula pendula)

A species that is native to all of Britain, but especially common in Scotland, the silver birch will colonise any area of ground left unattended. It is a fast-growing, relatively short-lived tree that shoots up in height for its first 20 years before reaching maturity at about 40 years old. The silver birch will tolerate a wide variety of habitats and soil types; ideally, though, the tree will do best in a sunny spot with sandy soil and plenty of drainage and is best planted in late winter or early spring. Once believed to be the source of twigs for witches' brooms, the tree now serves as a much-needed source of food for the endangered red squirrel, which eats its seeds. JM

Oak (Quercus robur)

The common or English oak is a large deciduous tree found throughout Britain and Ireland, although it isn't ideal for a modest-sized garden – each of these leviathans can grow up to 40m in height and live to 1,000 years. Deep rooted, with a large girth and a wide canopy, the oak is usually found in mixed woodland in basic fertile soils with a pH of 4.5 to 7.5. A single oak can host up to 500 species of insects and birds. The oak was believed to be a gateway between worlds in Celtic mythology, and the Navy built its fleets with its tough wood. Today, the wood is used to make casks for maturing wines and spirits. George Bull

Wild Cherry (Prunus avium)

One sure sign of spring is the sight of the white blossom of the wild cherry or gean. It also puts on a colourful show in autumn while it sheds its leaves. This tree is native to the UK and most of Europe, but does not grow in northern Scotland; its favoured soil is clay rather than chalk. Often found growing in beech woods, the wild cherry is equally at home in gardens, although it can grow up to 20m tall. To make a wild cherry bear fruit, more than one tree must be planted; alone, they are sterile. The small red cherries look attractive, and can be sour or deliciously sweet. Starlings and pigeons, however, particularly enjoy consuming the tree's fruit, as do wasps and small mammals. Impatient gardeners might note that the wild cherry is a fast-growing tree. RA

Scots Pine (Pinus sylvestris)

Folklore has it that Scots pines were used to mark the burial places of warriors, heroes and chieftains, while druids used to light bonfires made from the tree's timber at the winter solstice to celebrate the passing of the seasons. Growing up to 40m tall, the Scots pine typically lives for 150 years; some may survive for 300. The tree dislikes sea winds or high rainfall, and prefers light and sandy soils. The younger trees tend to have the classic conical silhouette, but as they mature can range from tall and narrow, with only a few side branches, to open and spreading with multiple trunks. It also provides a home for the red squirrel, which eats the seed from pine cones. One of the best places to see it in the wild is Rothiemurchus in the Cairngorms. GB

Rowan (Sorbus aucuparia)

Also known as mountain ash, the rowan, which can grow to 20m high, boasts white flowers which bloom in May and blood-red berries in autumn. These are a source of food for many birds, and are also used to make a jelly that is served with game dishes. Uncooked berries are unsuitable for human consumption. Rowans grow throughout Europe, Asia and North Africa. The tree's name is believed to derive from the Norse word "runa", meaning a charm, and rowans were traditionally planted in churchyards and outside houses to ward off spirits. On May Day in times past, a spray of rowan leaves was hung over doors to repel evil. RA

Common Alder (Alnus glutinosa)

The distinctive outline of this tree's long trunk and narrow crown is a common sight across Britain's streams and water courses. The common alder can grow at a rate of 0.5m a year and has been known to reach 25m. A member of the birch family, the alder's leaves are shiny and toothed, dark green on the top, with a paler downy underside. In early spring, male flowers appear as catkins, providing nectar for bees and a sought-after blossom for flower arrangers. In the garden, the alder is the perfect plant to use for a hedge, and is a good choice for marshy areas. Tanners used the bark as a dye before the arrival of synthetic colours. Used alone, the bark dyes woollens a reddish colour, known as Aldine Red, while the bark and young shoots combined produce yellow dye. JM

Spreading trees: Britain's leafiest regions - and the best woods to visit

Scotland

Glen Finglas, Stirlingshire

A 10,000-acre Trossachs jewel within the Loch Lomond and The Trossachs National Park, on the southern edge of the Highlands and renowned for its mountain, loch and woodland scenery.

North East

Pontburn Woods, near Durham

A mosaic of broadleaf and conifer woodland, 272 acres stretching from the River Derwent south towards Dipton.

Yorkshire & Humberside

Hackfall, near Ripon, North Yorkshire

A wild wood set in 350 ft gorge, near Fountains Abbey, a beautiful 110-acre expanse of grottos, surprise views, glades and rustic temples

North West

Great Knott, Cumbria

Great Knott Wood covers 85 acres on the south west shore of Lake Windermere, within the Lake District National Park.

East Midlands

Everdon Stubbs, Daventry, Northants

Documented since the 10th Century, the wood extends to 72 acres and is a designated site of Special Scientific Interest

East of England

Tring Park, Hertfordshire

Dating back to 1066, 261 acres of open areas dotted with large trees, chalk grasslands and wide range of wildlife and plants

London

Joydens Wood, Dartford

Joydens Wood, located on the south-eastern edge of London - only 13 miles from the city centre - hilly with a main valley.

South-east

Hucking Estate, Hollingbourne

Nestling in the Kent Downs Area of Outstanding Natural Beauty (AONW), a 580-acre rolling tapestry of bluebell wood and pastureland

South West

Bovy Valley Woods, Dartmoor, Devon

A beautiful network of three woods characterized by old meadows, ancient trees and babbling brooks, a total of 215 acres of picture-postcard scenery.

West Midlands

Credenhill Park Wood, Herefordshire

Ancient woodland covering 225 acres, located within the Hereford Hills, with steep slopes complete with ancient hill fort

Wales

Wentwood, Newport

A thousand acres of woodland, Wentwood is dominated by conifers, some of which were among the first of that species to be planted in the united kingdom, in the early 1700s.

Ulster

Monkstown Wood, Newtownabbey

A blend of mature wood and oak, ash, rowan, alder, wild cherry and scots pine species planted in 2000, this is a small gem wedged between industrial buildings and a river.

Roots to success How to plant the perfect tree

* "Anything you plant could be there for decades or centuries," Paul Underwood, the head gardener at the National Trust's Blickling Hall Gardens and Park in Norwich, says, "so give them room." Avoid walls, buildings and places that might have extensive foundations and underground cabling.

* Tailor the tree to your "microclimate". Are you in a "frost pocket" – a low-lying area that encourages frost – or a coastal area, which might receive salty spray?

* Consider the season. You can buy either "container-grown", "root-balled" (roots bound into a bundle) or "bare root" (simply dug out of the earth) trees. A container-grown sapling can be planted later in the year. Juvenile trees establish their roots quicker, but older – and more expensive – purchases have an immediate visual impact.

* Browse before you buy. Check out the tree's health. The mass of roots should roughly equal the mass of leaves and stems.

* Before planting, think about whether you'll need a stake to support the tree when growing. Small stakes allow trees to develop good anchor roots, but a more expensive, loftier support might be required in the windiest of sites.

* Dig for success. Mark out your area, about three to four times the size of the tree's root ball, and lift up the turf and remove any weeds. Excavate a hole one-and-a-half times the depth of the root mass. Prick the sides of the cavity (especially in a clay-rich soil) with a fork to help the roots establish. Remove the topsoil, put it to one side, and mix one part compost to four parts earth (which you'll need when planting).

* It's planting time. Hammer your stake into your hole, off centre, on the windward side of the tree, so that tree blows away from it. Remove the tree from its container and lay it on its side to tease out its roots. If container-grown, use a garden cane to check you are planting the tree to the same depth as it was growing in the container. Then fill in with the soil/compost mix.

* Water the tree before and after planting, and prune off any damaged stems. Apply compost as needed.

* Stay vigilant. "Keep a close eye on your tree over the first two years," warns Underwood. "Make sure it gets enough water, especially in drought conditions." Give it a balanced feed, such as Vitax or Growmore, every year and prune according to preference.

Rob Sharp