Nature Studies by Michael McCarthy: The small-leaved lime, lost tree of England

Some myths are so tenacious as to be virtually unshakeable, and one such is that the national tree of England is the oak. There is no Act of Parliament proclaiming Quercus robur to be an official symbol of Englishness, but there doesn't need to be, with a belief which has such deep roots in Middle England's psyche that David Cameron's Conservative Party ditched Margaret Thatcher's red, white and blue "torch of freedom" in favour of an oak tree as the new Tory emblem (although I notice that these days they tend to fill in the tree's outline with the Union Jack, just in case anyone doesn't get the point. Didn't Dr Johnson say that patriotism was the last refuge of the scoundrel?).

Steadfast, immensely strong and reliable, the oak was seen, at least in ideal terms, as standing for the English character, and there are many enduring connections with it in the English collective consciousness, such as the notion of Nelson's ships being "hearts of oak". Another is the memory of the Royal Oak at Boscobel House in Staffordshire, in whose branches the young Charles II hid from the pursuing Roundheads following his defeat at the battle of Worcester in 1651.

After the Restoration, this became the most famous tree in the land and was eventually destroyed by souvenir-hunters snapping off branches, although you can see one of its descendants at Boscobel today, and the legend lives on in pub signs: The Royal Oak is either the second or the third most popular pub name in the land, after The Red Lion and The Crown (depending on which survey you use).

But I also think that behind the cultural connections, there is a general sense of the oak belonging to England in natural history terms as well: great oaks still dot the landscape and there is a widespread belief that oak was the dominant tree of the Wildwood – the ancient forest that covered the country after the last ice age, before humans began to interfere with it.

Last week, I learned to my surprise that, for the English lowlands at least, this is simply not true: the dominant tree of the Wildwood was not oak at all, but a species with a mere fraction of oak's cultural resonance, indeed, one unknown to the greater part of the population: Tilia cordata, or small-leaved lime.

The land of limewoods; that's us, or at least that's what we were, in pre-history. We know this from pollen analysis, the study of the pollen of plants and trees which is often preserved in bogs and at the bottom of lakes, and can be identified and used to determine the vegetation characteristics of a given area at a given time. Although oakwoods did predominate in western England, Wales and the north-west, in the southern lowlands, small-leaved lime was supreme.

But while the oakwoods remain in the west to this day, the limewoods have largely disappeared, and in much of the country, T ilia cordata is now a rare and unfamiliar tree. No-one is quite sure why it went; it may have been climatic changes, or it may be the fact that lime grew on the land most suited for agriculture, and so was very readily cut down; and it is only in recent decades that we have understood that the lime was once, in effect, perhaps a better candidate than the oak for the title of the English national tree.

Oliver Rackham, our greatest woodlands expert, opened my eyes to this when I went to interview him in Cambridge last week about the row over the future of England's forests, and we fell to talking about their past, and in particular the Wildwood and its composition.

A key insight, Dr Rackham said, was that lime, which produces beautiful yellow flowers in July, is insect-pollinated, and therefore does not need to generate nearly as much pollen as oak, which is pollinated by the wind and has to scatter immense amounts of pollen far and wide. "So if you have a sample that contains 90 per cent oak pollen and ten per cent lime, it used to be thought that meant an oakwood with a few lime trees in it," Dr Rackham said. "It's now appreciated that it's more likely to be a limewood with a few oak trees in it."

Being shamefully ignorant of modern limewoods – and you can still find them – I asked him what they were like. "If left uncut for long enough, lime grows very tall and straight, forming 'cathedral groves'," he said. "It's reputed to be the tallest native tree. It's very densely shading, with particularly well-marked 'coppicing flowers' every time the wood is cut down."

There are other fascinations about the tree. It produces one of the best woods for carving, (limewood was the material used by Grinling Gibbons, the baroque master who was England's greatest wood carver); and the fragrant yellow flowers are used in an infusion which is called Tilleul in France, where it is as popular with herb tea enthusiasts as camomile is here.

But it is the place of small-leaved lime in our history which most catches my imagination. The truth is a quirky beast, not always according with our preconceptions, and even though the oak will never be displaced from its central position in our mythology, it is intriguing to learn that the ecological truth about Ancient England relegates oak to second place, and that the English Wildwood was really a forest of tall, dim, cathedral groves – it was the land Unter den Linden, as the famous Berlin boulevard is named, under the lime trees.

m.mccarthy@independent.co.uk