The Wood for the Trees

by Richard Fortey

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  THE TORTUOUS SAGA of the ghost orchid prompts me to make a thorough quartering of Grim’s Dyke Wood in June. It is too much to ask of my tiny piece of ground, I know, but that does not stop me peering closely at every beech-leaf-filled gulley. I will not miss a thing, I tell myself, and for half an hour I trudge like a botanising zombie up and down, up and down. For an instant, my heart stops. Here are two yellow stems arising from the ground and bearing flowers. There is no sign of a leaf, or anything green. So is it an orchid? The stems curve over at their apices like shepherds’ crooks where perhaps half a dozen yellow flowers hang down, almost in the fashion of our bluebells; however, these flowers are tubular. This is not a shape known from any orchid. This may be no ghost, but it still thrills like a sudden, strange apparition. The Red Data List records some of the most precious and uncommon species of plants in Great Britain,7 and this is one of them, in our very own wood! I have known it for many years as an illustration in the Reverend Keble Martin’s indispensable New Concise British Flora. In an even older book I have a list of all the wildflowers I have ever seen, which I have been ticking off since I was a boy: this is one plant that had remained persistently unticked. Nor is it some anonymous, tiny green herb. It is another special plant in the ghost orchid mould lacking all chlorophyll, a spooky spectre, and somehow implausible. It is called the Dutchman’s pipe, or if you prefer, yellow bird’s nest, and by scientists Monotropa hypopitys. I have never met a pipe-smoking Dutchman, but I would now recognise the shape of his favourite accoutrement.

  On my hands and knees, I brush away a few loose leaves concealing the bases of the stems of the new discovery. They look a little like blanched asparagus spears, complete with scattered scales. They are the only plants growing in the deep shade. They really do rise straight out of the ground. I would be willing to bet a hundred squirrel tails that if I dug down they would originate from swollen roots such as Eleanor Vachell found for Epipogium. I am not going to try it. A small beetle emerges from one of the flowers, having, I suppose, helped to fertilise it. Over the next few weeks I keep tabs on the small blooms: they last and last. The Dutchman’s pipe is not taking many risks when it comes to setting seed.

  Monotropa has recently been the focus of botanical research. In my old edition of Keble Martin—and in many later books—it sits all by itself in its own plant family (Monotropaceae). It seems that no expert could quite make up his or her mind where such a weird, penumbral paradox fitted into the grand scheme of plant evolution. In North America a related, almost supernaturally pallid species is known as the Indian, rather than Dutchman’s, pipe, or sometimes as “the corpse plant” (Monotropa uniflora), which suggests that we are never going to be able to escape the whiff of the graveyard in this chapter. When the techniques of molecular analysis to determine ancestry became widely available it was not long before both species of Monotropa were allied with a much larger plant group, the Ericaceae, the familiar heather (or blueberry) family, with something like four thousand species worldwide. The Dutchman’s pipe was, in its essentials, a heather that had lost everything above ground except the flowers. Now that I study them again, the flowers of Monotropa do indeed recall those of strawberry trees, blueberries or bell heathers—perhaps we should have known all along. Occasionally, science just reinforces common sense.

  The root of the ghost puzzle really is the root. All our ghostly plants, whether orchid or pipe, have similar-looking roots, which are tuberous and puffy. Both the loss of chlorophyll and the ability to thrive under the beech canopy are the result of special adaptations secretly hidden away underground. V. S. Summerhayes was right in essence: neither the Dutchman’s pipe nor the ghost orchid manufactures its own nutrients. But he was wrong to assume that these plants were what he termed “saprophytes”—that they sourced all they needed from the rotting leaf litter surrounding them. The explanation is both more complicated and much more wonderful than mere scavenging. Monotropa and Epipogium are playing parasitic piggyback on mushrooms. In the case of the Dutchman’s pipe, the fungus has been identified with an ordinary-looking mushroom that has been called the girdled knight (Tricholoma cingulatum)8—not exactly a regular “shop mushroom,” since it has a greyish cap and white gills, but constructed along the same familiar lines. Our pallid plant has given up any attempt to manufacture its own necessities in favour of stealing all it wants from its fungus host. Above ground, it needs to be nothing more than flowers and seeds. Like some Regency dandy feeding off colonial slavery, the organism can be all show and no hard graft. The distinctive roots of the plant reveal the truth: they are full of fungus, and modern techniques of DNA analysis allow the molecular biologist to identify exactly which species from a choice of thousands. When I started out in science as a botanising youth, this would have been impossible, but now it is almost routine procedure back in the laboratory.

  However, this is not the end of the story. For the fungus itself lives in an intimate association with beech trees in deep woodland. The “roots” of the fungus are masses of threads called mycelium. These threads move through the moist soil seeking out nutrients, and they are skilled in reprocessing all that mush and drift of rotting leaves. Mycelium is the workhorse of the fungus, while the familiar mushroom fruit body is just the culmination of the life cycle for spreading the minute spores of the species. Like many other fungi, Tricholoma forms a partnership with the roots of beeches, where it can live for many years. The threads of mycelium fully coat the growing tips of the roots rather as tight-fitting kid gloves enclose the fingers, and the fungal talent for acquiring important foodstuffs such as phosphates from the surrounding environment becomes essential for the healthy growth of the tree. The fungus-coated rootlets seek out valuable molecules. The fungal dressing is called mycorrhiza, which is simply a classical way of saying “fungus root.” Mycorrhiza makes for a reciprocal partnership, because the tree in its turn does what it does best—manufacturing sugars and other products of photosynthesis—and supplies them to the growing fungus, which cannot make them for itself. It is a symbiosis, an intimate growing-together. Like a well-honed comedy duo, each partner would fall flat without the other.

  So the Dutchman’s pipe is at the foppish apex of a ménage à trois. The beech works with sunshine and rainfall, and supplies the fungal partner on its roots with the means to quest for more exotic vital nourishment. Monotropa is a parasite on the fungus, so indirectly it too benefits from the photosynthetic work of the lofty beeches, and can dispense with its own green parts. The fungus supplies everything else. Freed from the need for light, the parasite can safely flower in deeply shady glades where nothing else can prosper.9 Nor does it have to flower every year. In a bad year for either tree or fungus it can hang on as a root or rhizome hidden beneath the litter, biding its time. Now we can understand the fickleness of those ghostly appearances. The spooks might really be there all the time.

  Cherry-picker

  A cherry-picker comes to the wood to access the canopy. Shane, the operator, a young man with dramatically pierced ears, has brought it all the way from Essex on the back of a truck; it is a special piece of kit. The contraption trundles through the wood on caterpillar tracks until it reaches a place where it is possible to shoot upwards through the trees. Then four legs like those of a spider with long flat feet extend outwards on to the firm ground to support a lifting platform. I am first in the queue. A harness is strapped to me, and I step gingerly with Shane on to the small, railed platform.

  Although they look quite neat, the telescoped shafts of the machine are capable of extending to more than ninety feet. The platform twists and swivels, guided by Shane’s handset, as it rises to avoid overhanging beech branches. The ascent is like passing through a series of extended curtains decked in fresh leaves. We rise speedily, the foliage occasionally brushing my face, and then—quite suddenly—we break through the canopy. We must be at least eighty feet off the ground. I am too fascinated to feel at all scared. The treetops billow out in all d
irections, an extraordinarily rough sea of breaking waves of foliage, and above, nothing but the sky. This is what a red kite would see soaring over the woodland in summer, with all the ground concealed except for rare clearings. A few beech trees have crowns that stand higher than the rest; I infer that one of them is the fine old tree in the middle of our wood, surely a hundred feet tall. Some are laden with the yellow-green cupules that will mature in the autumn. I spot a cherry tree keeping up with its neighbours in the race for the light. To the north, the edge of Lambridge Wood is lined with trees on its margin that have boughs bearing leaves all the way to the ground, like green waterfalls. A huge ash is more delicate; I am reminded of the graceful paintings of Corot, where trees are like gentle breaths.

  I have a vision of the whole wood as a tent draped with a canvas of leaves capturing sunlight for photosynthesis. Tree trunks are like immense tent poles supporting the whole structure, and sheltering inside the tent all the animals and plants I have discovered. From this high vantage point the Fair Mile is just one valley in the rolling landscape, with Henley Park and all the hills beyond, without any jarring buildings until the distance is swallowed up by the most gentle of mists. Henley tucked into its Thameside valley did not look very different in the eighteenth century. Only a conifer plantation in the lower part of Lambridge Wood seems inappropriately dark. I am surprised that there are not more birds up here. I was expecting small species like nuthatches and tits to be hopping everywhere through the high branches. Maybe my presumptions were primed by those television documentaries displaying abundant life in tropical canopies. Things might be different in the Temperate Zone.

  I must not hog the heights. A team of entomologists from the Natural History Museum wants to get up to the canopy to sample the insects that live among the leaves. Shane’s machine lifts the visitors up one by one. Their fine nets swish through the canopy, each researcher after his or her own favourites: dipterists in pursuit of flies, coleopterists chasing beetles, hymenopterists after tiny insects belonging to the same order as wasps. A dozen swishes, and a skilled collector of tiny insects can gather enough specimens for weeks of work examining the veins on the wings or the hairs on the legs—the stuff of accurate taxonomy. Earlier in the day we had seen the largest British wasp—the hornet (Vespa crabro)—buzzing lazily through the trees by the woodpile. Entomologists are less alarmed by this venomous creature than are ordinary souls; they know it will not attack unless provoked. A second site allows sampling through oak canopy to provide further species, including a spectacularly large weevil (Curcilio venosus) that develops in acorns; everyone gathers round to admire its oddly extended mouthparts, almost elephantine. Samples are collected in jars to transport back to the Museum for accurate identification. But one species, Agrilus angustulus, immediately sets a beetle man or woman’s heart aflutter; for this is a small jewel beetle, a brilliant iridescent green, belonging to a family (Buprestidae) that is much commoner in the canopies of tropical rainforests. Like the yellow bird’s nest, it is “nationally scarce” in the current British classification recording wildlife that is worth protecting.

  I would never have been able to find, let alone identify, such interesting items, and my heart rejoices that there are still experts who are able to add them to the cast of characters in the wood. Many more samples disappear with their keepers back to the vaults. The gurus will report back to me later.10

  Nettle Fertiliser

  One corner of Grim’s Dyke Wood grows stinging nettles. This corner is nearest to the ghost cottage, so it is possible that the ground was disturbed there, since nettles prosper in such places. Nettles provide food for several of our species, including the larva of the charming little Nettle Tap moth, Anthophila fabriciana. They are also something of a nuisance, as ours seem to have an exceptionally potent sting. By late June they have grown to full stature. A satisfactory form of vengeance is to be had by turning them into fertiliser. Nettles sequester all kinds of plant nutrients. Strong, thick gloves are needed to pull them up, and then they can be packed into a waste bin with a tight-fitting lid. I scrunched up the leaves and stems as I stuffed them into the bin and pushed down. Now the mush was covered with water (rainwater is good), the lid replaced, and the brew was allowed to rot down. Adding a weight helped. I used a couple of large flints (from the wood, naturally) resting on a piece of wire mesh. Next, I left the vessel in a corner of the garden and forgot about it for a month, perhaps longer. It all fermented in my absence, and the liquor really ponged when it was ready for use. I put a clothes peg on my nose and removed and threw away the soggy stems on to the compost heap. I had to dilute the remaining liquor at least fivefold before using it to water tomatoes, beans and the like. It worked as well as expensive commercial fertiliser.

  4

  July

  Gloom

  The rain never stops. The sodden woodland is dark and depressing. Even the birds have stopped singing, except for one bewilderingly optimistic thrush relaying his mantras five times over and over, as if pleading for something. Fungi love damp, but for some reason they too seem discouraged. The only flower still evident is enchanter’s nightshade, now showing modest spikes of tiny pink flowers, two petals apiece, and creeping along where the bluebells once were. Who was this enchanter, and why was this little plant his personal nightshade? Where has all the spring exuberance gone? Everything seems portentous. On such a day hardly any light penetrates the canopy. As I look upwards, the leafy roof of the wood might just as well be some unspecified infinity, for all I can see of a junction with the leaden sky. Things merge together above my head. It could be a high mist, or else a trick of the light; I can’t tell. Boundaries are smudged out in the wet.

  As for the beech trees, rain proves that none are actually vertical. The water always seems preferentially to dribble in rivulets down one side or another of any trunk, darkening it, feeding a million micro-organisms into a brief hegemony. I try to imagine how many amoebae and paramecia rejoice single-celled in the general sogginess. This is a time for mobile microbes to take charge of their slippery fiefdom. The raindrops themselves have allied to form a kind of aggressive bomber air force. All the leaves have long since given up trying to shield those creatures like me who cringe below them. Individual drips now coalesce into giant drops that plummet directly down the back of my neck: huge, unnatural blobs that pass through my inadequate mackintosh. Damp stains spread upwards from the forest floor, and downwards from my collar.

  Water is backing up along the paths, so I cut through the big clearing. How much smaller it seems now that the trees are leaning out to their greatest extent. Rain blurs my vision. Arching, vicious bramble stems snag my trousers; I could swear they were deliberately trying to trip me up. I could fall and cut my hand on one of the flints. My own wood suddenly seems to have a malevolent side. I can see how easy it would be for unprepared travellers to lose their way. A sudden, involuntary shudder, and I understand why extensive woods were once thought of as wilderness—unfriendly wastes populated by unreliable sprites. Shakespeare described such a forest in The Two Gentlemen of Verona:

  How use doth breed a habit in a man!

  This shadowy desert, unfrequented woods

  I better brook than flourishing peopled towns.

  A desert: a place deserted, or a place of desolation, and assuredly not one for quiet contemplation or spiritual refreshment. By Shakespeare’s time the wolf was probably extinct in Britain, so the fearsome bogey that inspired so many folk tales in rural Germany was no longer a threat. But dense woods surely continued to seem full of dangerous shadows, some of them real enough, like footpads and desperate fugitives. Even the trees look different this morning: Is that the same Elephant Tree? I am sure it was less massive yesterday, and now it is somehow intimidating, even looming in an odd way. That holly scrub is so dark it looks like a hole in the fabric of nature. I lick a bleeding scratch on my wrist inflicted by an old blackberry vine. The salty taste of blood mixes with the blandness of rainwater. This
is a strange day, all right. It is a day for delving into the dark past. I think I am alone, but I am not. A lone dog-walker deeply protected by a sensible Barbour jacket and cloth cap is whistling for Rover continuously, and marching along Grim’s Dyke, head down, with more urgency than might seem necessary. I cannot see his face. We do not exchange pleasantries.

  Grim

  The south-western edge of our wood is defined by a bank a few feet high. It is steeper on our side, though hardly dramatically so. Running along beside it, and tracing the length of our boundary, is a shallow depression, a gulley if you wish, about ten paces across. Mature beech trees grow within the gulley, so it is obviously not a new feature. Flints break through to the surface on either side of it, suggesting bedrock brought up by the excavation of a ditch of some kind. It does not look like a particularly important piece of archaeology, and the wood is fairly dotted elsewhere with depressions and banks that are not so different at first glance. However, this gulley extends well beyond our piece of woodland. I have followed it through most of Lambridge Wood where it continues, quite straight, through beech grove and holly jungle, a little more defined in some places than in others, occasionally hard to see, in the direction of the old manor house at Greys Court. It is marked on all the old maps, usually by a double line of hatching.