"England shall bide till Judgment Tide,/ By Oak, and Ash, and Thorn!"
Was Rudyard Kipling the first "tree nationalist"? No well-turned phrases about sycamore or the sweet chestnuts he would have known in his corner of the Weald appear in "A Tree Song". The trees which moved the poet were the quintessentially English - oak of the clay, ash of the loam, thorn of the Down.
So Kipling would have understood the modern debate about planting only trees native to Britain, or, better still, native to a particular locality. Nor would he have jibbed at the label "tree nationalist". It might discomfort the politically correct but it is a much livelier description than being known as an advocate of "trees of British provenance".
The arguments of the tree nationalists contain linguistic echoes of uglier nationalisms, with talk of "genetic pollution" and targeted eradication of non-native species. It is anti-foreigner stuff, but thankfully only trees are at issue.
Full tree citizenship is extended to those varieties of trees established in Britain when the land bridge with the rest of the continent disappeared tens of thousands of years ago. Thus Britain has only one true pine, the Scots pine, plus yew and juniper.
All the other needle and cone bearing trees which provide the mainstay of the timber and pulp business are foreigners. So too is the sycamore, though few trees have proved as rapaciously well-adapted to British conditions. It provides hard, close-grained timber and is most famously used in violin backs. Sweet chestnuts were introduced into Essex by the Romans, who loved the fruit, and the majestic London plane is a hybrid of American and Oriental varieties.
Concern about native trees is a relatively recent phenomenon - part of the great green awakening of the past couple of decades. It certainly did not bother Capability Brown and the other landscape gardeners of the 18th century who made liberal use of foreign stock. A lot of oak planted over the last 200 years was imported from Germany or Holland because it was believed it would grow better. Exotics such as cedars of Lebanon, redwoods and cypresses were introduced and Scots pine were planted across heathy areas of southern and east England - way beyond the tree's natural patch. Consequently, the tree-scapes we see today, though familiar, are very often non-native.
So isn't it rather late to argue for tree nationalism? The Woodland Trust thinks not. The charity cares for more than 38,000 acres of woodland where it plants only trees of British origin. For example, at Park Farm, an 180-acre site with the planned National Forest in the Midlands, the Trust is planting over 100,000 oak trees grown from seed collected locally in Leicestershire.
The story of the oak is a good illustration of the Trust's case that using native stock is a surer way of preserving a balance between trees and the wildlife they support. Green looper moth caterpillars feed on the young leaves of the oak and caterpillars in turn are important food for birds such as blue tits.
"If the blue tit's breeding cycle is keyed into the expectation there will be green looper caterpillars to feed to its young, then the time when the oaks come into leaf is vital," explained Richard Smithers, a Trust ecologist. "Trees of different origin come into leaf and fruit at slightly different times of year. Stock from the continent tends to come into leaf two or three weeks earlier than native trees."
Motorway drivers may have noticed that hawthorn bushes planted on the embankments often blossom a fortnight or so earlier than older hedgerow bushes. They underline Mr Smithers' case. Most motorway hawthorns were imported from elsewhere in Europe and follow a slightly different cycle.
The previous government set a target of doubling the UK's woodland within the next 50 years. The Trust is pressing for the use of native stock wherever possible. It is not trying to turn the clock back in most woodland, but where sycamore or the hated rhododendron invades ancient woodland, such as the oak woods of Snowdonia, it is attacked. "Rhododendron bashing" is the most popular task of Trust volunteers.
One of the purist exercises in tree nationalism is underway in the Highlands of Scotland with attempts to regenerate the great Forest of Caledon. Isolated remnants remain in places like Glen Affric and in the glens of the Cairngorms. But though magical in themselves these oases of Scots pines contain few new trees. Most are over 150 years old. "Granny" pines of more than twice that age are producing fertile cones but the saplings are eaten by red deer.
The best hope for regeneration of forest lies in culling the excessive deer numbers. On the 77,5000-acre Mar Lodge Estate on Deeside, an ambitious cull instigated by the new owners, the National Trust for Scotland, is already showing the job can be done without erecting miles of anti-deer fences. The fences are a deadly hazard to the rare capercaille and blackcock.
The Forestry Commission has changed radically since the days when it was identified solely with blanketing the hillsides with sitka and Norway spruce. Though pursuit of the best commercial return still dominates the choice of trees for its forests in south-west Scotland - and that means the American sitka spruce - elsewhere planting often reflects "social values". That means broadleaf trees or Scots pine. Subsidies to private growers also favour native woodland.
Dig deeper into "tree nationalism" however and more philosophical questions are raised. As Donald Thompson, head of the Commission's forest practice division pointed out, Norway spruce was marching steadily west towards Britain and had only about another 20 miles when the Channel was formed. Man carried it over but why should humans be regarded as any less a part of the natural distribution process than squirrels, birds or the wind?
And more perplexing still, what is "nativeness"? According to Mr Thompson, it is "really a human perception based on what people regarded as `not natural' to a particular place. But plants are busily trying to get everywhere, and trees are no different".