Everywhere I have travelled plants have surprised me by their dogged loyalty to place, even to the point of defining the genius loci, and then by their capricious abandonment of home comforts to become vagrants, opportunists, libertines. I’ve seen ancient goblin trees develop wandering branches as promiscuous as bindweed shoots, which might equally well lope off into the countryside or jam themselves into a city wall. I’ve marvelled at tropical orchids living off air and mist. Plants, looked at like this, raise big questions about life’s constraints and opportunities–the boundaries of the individual, the nature of ageing, the significance of scale, the purpose of beauty–that seem to illuminate the processes and paradoxes of our own lives.

Our traditional cultural approach has been dominated by analogy. For at least 2,000 years we’ve tried to make sense of the barely animate world of plants by comparing its citizens to models of liveliness we understand–muscles, imps, electric machines and imperfect versions of ourselves. Daffodils become dancers and ancient trees old men. The folding or falling of leaves is a kind of sleep, or death.

we can think more clearly about our own lives because we have taken plants into the architecture of our imaginations.

the fashionable Victorian fad for ‘the Language of Flowers’, which ascribed plant species with a code of arbitrary ‘meanings’ which had no connection whatever with the lives of the organisms themselves.)

The long habit of seeing resemblances and analogies has been a defining feature of our species since the dawning of the modern mind in the caves, 40,000 years ago. I can’t help looking for metaphors in ice age art, any more than its creators could resist inserting them. So

In Egyptian art, already well populated with birds and animals, notional plants begin to appear about 2500 BC. A thousand or so years later the pictures are beginning to be impressively accurate, and often embedded in some kind of narrative of enclosure.

Plants also have a special relationship with time that makes photography’s unique ability to ‘freeze the moment’ of little significance.

The concept of ancient woodland was a radical one in the 1970s. The popular wisdom was that woods were human artefacts, and could only begin their lives by being deliberately planted. The idea that they continually regenerated themselves, and in some places had survived on the same site for thousands of years, was heretical, and is still uncomfortable to those brought up in a culture of human dominance.

I heard a rumour that a retired vicar who lived in the next road was fond of planting out wild species in provocative places. I liked the idea of the Reverend Moule buzzing round the countryside on his antique autocycle with its panniers stuffed with sheaves of feral vegetation, like some botanical evangelist.

it’s not without irony that the first image of a significant tree is from Mesopotamia, springboard of the agricultural revolution that was to destroy most of the world’s forest over the next 5,000 years. It’s on a Sumerian seal from circa 4500 BC and shows a tree of life between two gods. The female goddess is probably Isis, and she has a snake, a symbol of water, beside her. The tree is smaller than the gods and appears to be on some kind of stand, but it is obviously a palm, with symmetrically arranged leaves and two prominent drooping dates.

Yggdrasil is one of the more intriguing trees of life, since it has some relation to the real ecology of the forest. In the myth it is the focal point of the transmutation of the sun’s energy and of a set of reciprocal relations with other organisms.

The fact that trees have perfectly adequate reproductive systems began to pass out of popular consciousness. We now believe we have to plant them to guarantee their presence on the earth. A thoroughgoing anthropomorphism continues to infect our judgement of their form, too. Natural signs of ageing are interpreted as disease, and disorderly growth as an indication of inferiority. Both are frequent preludes to arboreal cleansing.

A 250,000-year-old yew spear found at Clacton in Essex is the world’s oldest surviving wooden artefact.

What unnerved me was how dull I was finding the Great Yew. It had none of the panache and power and narrative fascination of deciduous trees one twentieth its age. It had no great burrs where branches had been lopped, no self-pleachings, no cryptic caverns. But as soon as I had admitted this to myself, I realised what a presumptuous reaction it was. Historical aura, visual glamour, legibility to human readers–none of these have the slightest relevance to the tree’s existence, except perhaps to how it is treated.

The conundrums of ancient yews–Were they sacred totems, planted by Neolithics? Were churches sited where yew trees already grew?–are seductive puzzles, but are really more about our social preoccupations than the life of the yew. At Fortingall it is as if we can’t see the tree except in our own attachments to it; as if we hope its origins, laid bare, might reveal lost human sensitivities or beliefs. The tree itself, for itself, recedes. It already resembles an inanimate standing stone, confined in a space defined by us and not far off being the next piece of paving in the tourist trail.

Most trees go through three distinct stages of growth. For their first fifty to a hundred years they grow comparatively quickly, and the new wood builds up in a series of wide annual rings in the trunk. In middle age (100–500 years) the size of the crown stabilises, the annual increment of new wood remains constant, and the corresponding rings become thinner and more uniform. In old age, the tree may actually shrink as branches fall off or die back, the production of new wood declines, and annual rings become very thin.

The oldest living organisms in the world are probably the subterranean mycorrhiza of ancient forest fungi. They’ve been there since the woods sprang up, tens of thousands of years ago, and live in an intimate partnership with the tree roots, without which neither could survive. The root and fungal tissues are as imbricated as if they were a single organism. The tree supplies the fungus with sugars, the fungus filters minerals from the soil into the tree’s roots. Sometimes these fungal systems stretch throughout a wood as an unbroken network of subterranean tissue, entwined with the roots of most of the trees in the forest, an immense feeding and communication cooperative which may weigh hundreds of tons.

A clone of 47,000 quaking aspens in Fishlake Forest in Utah–known as Pando, the ‘Trembling Giant’–is, at approximately 80,000 years, probably the oldest mass of connected tree tissue, and weighs in at 6,600 tons.

the bristlecones’ major strategy for survival into extreme old age is, counter-intuitively, to take itself very close to death. As an already ancient tree edges into venerability much of the wood dies back, often leaving just a wisp of living tissue connecting the roots to a handful of twigs. Effectively it has become torpid, embalmed, reducing its growth–and therefore its needs–to almost nothing. The stresses of old age in bristlecones are purely climatic, not metabolic.

The ideology of veteran tree conservation–certainly in the USA–still echoes with the nineteenth-century conviction that the anciently pristine may be the God-given route to the future.

They have unique ‘corraloid’ roots which live in symbiotic partnerships with algae able to fix atmospheric nitrogen–a trick which the bean family also achieved but 100 million years later.

They also, as a family, have a strong propensity to throw up new subspecies and hybrids, adapted to quite specialised niches, providing yet another route to survival and the colonisation of new territory.

By 1912 there was only one short and damaged stem of the original plant left in the wild. The priority of conserving a species in its wild habitat wasn’t properly understood at the time, and four years later the Forestry Department arranged to have this last surviving specimen dug up and sent to the Government Botanist in Pretoria, where it expired half a century later.

Hybrids between native rarities and more vigorous intruders are despised and sometimes destroyed because, from a niggardly view of biodiversity, they are diluting the genetic purity of the original.

In the 1990s Sacks visited a string of islands in the Pacific where a strange endemic colour blindness exists that might possibly be related to regular consumption of flour made from cycad seeds. He tells of one evening on Rota, a small island east of Guam, when he sits on the beach, amongst cycad trees that come down almost to the water’s edge. The sand is littered with their giant seeds, and fiddler crabs are emerging to scissor their way in for the kernels. A light wind has got up, and the strengthening waves are catching some of the seeds and drawing them into the sea. Most are washed back onto the shore, but Sacks watches one surfing the waves, beginning to edge away and perhaps on the beginning of a journey across the Pacific. There is a chance that it will pitch up on another island and germinate; and a more remote but thrilling possibility that it might eventually hybridise with another cycad species there, and extend the family’s survival opportunities into the future.

something essential about the Quercus family. It’s opportunist, mutable, full of hybrids and intensely local varieties.

circumstance.Q. coccifera isn’t killed by felling, fire, shade or sheep. It regrows from the stump or rootstock, and the harder it’s grazed the more protectively spiny the new leaves become. Low-intensity browsing tends to push the regenerating oaklet into the shape of a classical column, slightly ruined but determinedly upright. The shoots around the base of the shrub spread out laterally until animals are unable to reach the centre shoots–which then grow upwards, allowing the oak to ‘get away’. It may eventually become a mature tree with low branches, at which point agile browsers can scramble up and edge their way along the woody tightropes, munching foliage just as they do on the ground. It is an extraordinary sight, trees bearing animals like fruit, with sheaves of shoots, browsed bare of leaves, rising vertically from the main horizontal branches. Historical ecologist Oliver Rackham calls them ‘goat pollards’.

The north European oaks Q. robur and Q. petraea can be split cleanly, even with stone axes, and flat oak planks–imaginatively provocative artefacts in a world dominated by naturally curvaceous forms–paved the earliest surviving European walkways. The Sweet Track that crosses the Somerset marshes in England is surfaced with oak planks, supported by a scaffolding of ash, lime, elm, alder and oak poles, almost certainly grown in worked coppices. The planks have mortises bored in them so that they can be pegged to the framework. The wood is so well preserved that recent advances in dating trees by their growth rings has placed the cutting of the wood precisely, at between the years 3806 and 3807 BC.

struck by lightning and burnt hollow.

It is a striking but well-known fact that the oak of other countries, though lying under precisely the same latitude as Britain, has been invariably found less serviceable than that of the latter, as though Nature herself, were it possible to indulge so romantic an idea, had forbad that the national character of a British ship should be suffered to undergo a species of degradation by being built of materials not indigenous to it …

an inherent property of self-organised systems.

Tree forms follow ‘the axiom of uniform stress’. The stresses they experience have to be distributed evenly over their whole structure, otherwise there are weak spots.

fractalism. Structural patterns echoed at an ever diminishing scale are widespread in nature, from river deltas to snowflakes, and appear again to be self-organising according to mathematical and mechanical laws.

Living plants are subject to unquantifiable and unpredictable stresses. They’re bent in the wind, raddled by fungus, shaded by their neighbours. Every Platonic pure intention is overthrown by the realities of life, which is not to achieve perfect form but to survive.

From the plant’s point of view the baptism of cultivation was a mixed blessing. It meant, usually, a great broadening of the variety of forms in which a species could exist, as humans selected or cross-bred for traits they found desirable. Colours, tastes, hardiness, handsomeness could all be teased out from the rich potentialities of a species’ genome. In the extreme case of the domestic apple some 20,000 distinct varieties are believed to have been developed from one aboriginal species. But these pampered variants are often bought at a cost. The development of copious fruiting may mean the loss of disease resistance. Exuberance of petal may mean absence of scent, and therefore of pollinators, as in many rose varieties. It is rare for a portfolio of vegetal qualities regarded as valuable by humans to coexist with the characteristics a plant needs to survive, unassisted, in the wild. Most of the millions of modern cultivated plants would become extinct within a generation if humans were to vanish from the planet.

As plant remains began to build up a thin layer of soil, and the temperatures rose still further, so the first trees began to arrive about 9000 BC–birch and pine, soon followed by abundant hazel, the Burren’s keystone species. The big forest trees, oak, elm and ash, came not long after. By 6000 BC most of the lowlands were covered by a patchy mantle of mixed deciduous woodland,

the first farmers arrived around 4000 BC (they came by boat, as the rising sea had broken through the land bridges joining Britain and Ireland to the continent more than 1,000 years earlier). The new pastoralists introduced a herding system which was a reversal of the traditional transhumance in their European homelands. They took the cattle down to the grassy lowlands in summer, and back up to the rocky uplands in winter,

Around 3800 BC there was a sudden and mysterious collapse of the elm population across Britain.

an early but by no means primitive form of coppicing. The more they’re cut, in a cyclical programme that can continue indefinitely, the straighter and more even their regrowth becomes. This may have been the way that hazel was grown for the wattle huts of the same periods. But it also, unusually, coppices itself. As well as a cluster of thick poles, which grow upwards in the form of multiple trunks, hazel is continuously putting up sheaves of new straight wands from its base. This is how it grows naturally, even when unbrowsed and uncut. Hazel must have been a favourite material for early Neolithic woodworkers.

Bob and John were crouched over the plant with the attentiveness of stoats contesting a rabbit,

The attachment of a precise name is irrelevant to the lives of plants themselves, which are continuously evolving new varieties (and therefore new labels) in response to changes in circumstance. Orchids especially are a promiscuous tribe whose members are always throwing up novel forms and hybrids. But I’m comforted by the act of naming. It’s a kind of befriending, a recognition, however temporary, of individuality and provenance.

evidence of the first expert weaving is from about 1000 BC, in the Indus Valley.

In the fifth century Herodotus, one of the more reliable classical commentators, reported, ‘The Indians have a wild-growing tree which instead of fruit produces a species of wool similar to that of sheep, but of finer and better quality.’

Pliny the Elder finds it has migrated further west, and recognises the pods as, botanically speaking, a seed-containing fruit: ‘The upper part of Egypt, facing Arabia, produces a shrub which is called gossipion … The fruit of this shrub resembles a bearded nut, which contains a soft wad of fine fibres which can be spun like wool and which is unsurpassed by any other substance in respect of whiteness and delicacy.’

It looks as if cotton had been a cultivated crop in Central and South America for at least 2,000 years longer than in Asia.

Zea mays is prone to a good deal of diversity, and highly promiscuous. In cultivation, sports (spontaneously different forms) often crop up in which the kernels are coloured, or fatter, or lie in multiple rows, or possess high levels of sweetness.

as maize began to radiate geographically across central America, and then into the northern and southern reaches of the continent, it also radiated genetically, as different forms were favoured and propagated to meet different tastes and cultural needs. Its spread through human and genetic space has been one of the longest and most complex exercises in amateur (and often unintended) plant domestication, yet one which would have been impossible without maize’s own genetic inventiveness.

turn unappetisingly gummy on being cooked. But they were highly prized in Peru and Bolivia for fermenting into maize beer, or chicha, important in religious ceremonies and as a recreational drink. Modern Peruvian sweetcorn destined for chicha is a bizarre crop when compared to conventional corn. The cobs are almost spherical, as big as an orange, with many rows of irregular kernels which each taper to a point. They vary in colour from pale lemon yellow to deep Chinese red.

The notion that, in rainforest ecosystems, ‘fertility’ exists in and is circulated through the vegetation, not the soil, is still not understood by many modern agronomists.

At the point of highest demand in the mid 1990s almost 100,000 pounds were gathered annually in the states of Kentucky, West Virginia and Tennessee alone. Collectors receive an average of $ 500 a pound–which makes ginseng the most valuable plant crop in the United States.

the persistent human conviction that we are the focal point of all biological activity.

The generation of biological forms (what we call biodiversity today) and the tendency of all living systems to become progressively more diverse and complex fly against the cosmic gloom of the Second Law.

Roughly 4,000 years ago apple grafting was discovered, inspired perhaps by the glimpse of a natural pleach between two chafing branches. From this point it became possible to perpetuate favoured varieties by surgically implanting a slip onto another apple stock.