MACALLÚ FIELD GUIDE 06
UNDER THE CANOPY
What grows when you stop looking at the trees
When we walk through a wood, most of us look at the trees first. We notice how tall they are, whether the light is coming through the branches, whether the path is wet and perhaps whether there is somewhere dry to sit.
But there is a lot happening underneath them that is very easy to walk past.
Around Killarney, the damp climate creates exactly the sort of conditions that mosses, ferns and other woodland plants love. They grow over stones, along old walls, around the bases of trees and sometimes directly on the branches above you. In the wetter parts of the woods, almost every surface seems capable of becoming somewhere for something else to grow.
Some of it is obvious. Bracken can reach almost to your waist in summer and holly is difficult to miss. Other things are much easier to overlook. A fern may be growing out of a crack in a rock. Several different mosses may be covering what looked, from standing height, like one green patch. A tiny plant may have been living on the same damp bank for years without anybody walking past ever noticing it.
You do not need to know the names of everything.
This is really about getting a little closer and looking properly. Turn over a fern frond and see what is underneath it. Look at the moss growing over a fallen branch. Notice which plants seem to prefer the wet places and which appear where the light reaches the woodland floor.
And every now and then you may find something with a much stranger story than you expected.
THE GREEN CARPET
Mosses and liverworts
Moss is probably one of the first things you notice in the wetter woods around Killarney, although most of us don't really look at it. We register that a wall is green, or a stone is soft-looking, and keep walking.
Get closer and it becomes much less uniform.
Some moss grows in little cushions. Some looks feathery. Some creeps tightly across bark and stone, while other patches become thick enough that another plant can begin growing on top of them.
Killarney's old woodlands are particularly rich in mosses and liverworts — together known as bryophytes — and the National Parks and Wildlife Service considers the woods internationally important for their oceanic bryophytes. In some places the rocks really are covered in a thick green mantle of different species.
You don't need to learn all their names to appreciate them.
Can moss tell you which way is north?
Sort of.
You may have heard that moss always grows on the north side of a tree and that, if you are lost, you can use it as a compass.
There is some truth behind the idea. Moss needs moisture, and in the northern hemisphere the north-facing side of a tree often gets less direct sunlight, so it can stay cooler and damper. Moss may therefore grow more heavily there.
But may is the important word.
Rain, wind, the shape of the tree, nearby vegetation, water running down the bark and local shade can all change where moss grows. It can quite happily cover every side of a tree if the conditions suit it. So by all means notice where the moss is thickest, but if you are actually lost, use a map or your phone rather than trusting a particularly enthusiastic patch of moss.
And what is a liverwort?
You will probably walk past liverworts without knowing you have seen them.
They are relatives of mosses and like many of the same damp places. Some look leafy and moss-like while others form flatter green growth across rock, bark and wet soil. Around Killarney they are part of that extraordinary little world growing over surfaces that would look bare in a drier climate.
If you cannot tell whether something is moss or liverwort, don't worry.
Most people can't.
The useful thing is simply to realise that the green covering a rock may not be one plant at all.
FERNS
Turn the frond over
Ferns are easier.
Or at least we think they are.
Most of us can recognise something as a fern without having the faintest idea which fern it is, and for this guide that is a perfectly good place to start.
Ferns are ancient plants. They don't produce flowers and they don't make seeds in the way flowering plants do. They reproduce using spores, and once you know that, there is a very easy thing you can do the next time you find one.
Turn a frond over.
Depending on the species and the time of year, you may see rows, stripes or little round patches underneath. These are structures associated with the production of spores. Suddenly the brown marks you might otherwise have assumed were damage become the interesting part of the plant.
The fiddlehead
Before a fern frond opens, it is curled tightly into itself.
This young curled frond is often called a fiddlehead, because it looks like the scroll at the end of a violin, or a crozier, after the curved staff carried by a bishop.
Watch the same patch of ferns through spring and you can see these coils gradually uncurl until the entire frond is open.
It is one of those things that has probably been happening beside you every spring without requiring you to notice.
COMMON DOESN'T MEAN UNINTERESTING
Bracken
Bracken is not rare and it is not particularly delicate. In the right place it can take over enormous areas and in summer the fronds can become so tall that you are walking through them rather than beside them.
That makes it easy to dismiss.
But underneath the ground is a network of rhizomes — thick underground stems that store water and carbohydrates and allow the plant to spread over surprisingly large areas. This is one of the reasons bracken can return again and again even after the visible fronds have disappeared for winter.
People have found a remarkable number of uses for it. Bracken has been used as animal bedding, thatch, fuel, packing material and as a source of potash for making soap and glass. Its starchy rhizomes have historically been dried and ground to make flour in some places, and young fiddleheads have also been eaten in several cultures.
Bracken contains toxic compounds and substances associated with cancer, and cooking does not remove all of them. There are plenty of things our ancestors used because they had little choice that we do not need to recreate now.
There is another side to bracken that is easy to overlook. Dense stands provide cover for wildlife and habitat for insects, birds and small mammals. But when it becomes too dominant it can also suppress other vegetation.
So even something this common is neither simply useful nor simply a nuisance.
TWO KINDS OF FROND
Hard fern
Hard fern is one to look for in the damp, acidic woods around Killarney.
It tends to grow in a neat rosette and, once you start noticing it, you may realise something slightly odd: it can appear to have two different kinds of leaves.
It does.
The broader fronds spread or arch outwards and do most of the normal work of the plant. The narrower, more upright fronds are the fertile ones and carry the spores.
That is quite a useful identifying feature because the plant can look almost as though two different ferns have decided to occupy the same spot.
Hard fern likes damp, sheltered conditions and is one of the characteristic plants recorded through Killarney's oak woods.
THE FERN THAT DOESN'T LOOK LIKE ONE
Hart's-tongue fern
This one hardly looks like a fern at all.
Instead of being divided into lots of little leaflets, each frond is one long, glossy green blade. The name comes from the old word hart, meaning a male deer, because the frond was thought to resemble a deer's tongue.
If you turn one over, look for the long brown or orange lines underneath. Those are the spore-producing structures. They can look almost like somebody has drawn rows of little marks across the back of the leaf.
It likes damp, shaded places and can grow on banks, rocks, old walls and mossy branches.
This is a good fern for beginners because once you know it, it really doesn't look much like anything else.
NOT NECESSARILY GROWING IN THE GROUND
Polypody
Then there is polypody.
It has the fern shape most of us expect, but the fronds are simpler and almost ladder-like, with a row of finger-shaped divisions running along either side.
Turn one over and you may find neat round dots on the back, yellow to orange when fresh. Those are the sori containing the spores.
The more interesting thing around very damp woodland is where polypody can grow.
Not necessarily in the ground.
In humid woods it can establish itself on moss-covered branches and trunks. In Killarney, thick moss on old horizontal branches can support polypody, and even small holly and rowan saplings can appear in the angles of branches.
Once you notice that, the idea of a tree as one individual thing becomes a little less obvious. One tree can be holding an entire collection of other plants several metres above the ground.
THE FERNS THAT ALMOST LOOK LIKE MOSS
Filmy ferns
Killarney also has filmy ferns.
They are much more delicate than the big ferns we are used to seeing, and in very humid woodland they can spread over wet rocks and deadwood so finely that they almost look like part of the moss.
That is possible because these woods stay extraordinarily humid. Filmy ferns can grow luxuriantly across damp rock faces and deadwood in Killarney's oak woods.
You may not identify one confidently while you are walking.
That doesn't really matter.
If you find yourself looking at a damp rock wondering whether the tiny green growth is moss, fern or something in between, you are probably looking closely enough for this guide.
THE FERN PEOPLE LOVED TOO MUCH
The Killarney fern
There is one fern around Killarney that deserves its own story.
The Killarney fern is delicate, translucent and extremely fond of places that remain wet and sheltered. It grows beside waterfalls, beneath overhanging rock and in dark crevices where humidity remains high.
Once it was much more widespread around Killarney.
Then people decided they wanted it.
During the nineteenth century, Britain and Ireland developed something close to an obsession with ferns. Ferns were collected, cultivated, displayed and sold, and rare species were particularly desirable. The Killarney fern was commercially collected so heavily that populations around Killarney were severely depleted. Only a few populations now survive in the district.
Today it is strictly protected in Ireland.
So if you are fortunate enough to recognise one, leave it exactly where it is.
There is probably something worth remembering in the fact that people once loved this plant so much that they nearly removed it from the place they loved finding it.
A photograph is enough.
THE UNDERGROWTH
Not everything untidy needs tidying
There is a tendency to look at undergrowth and think something needs to be done about it.
Brambles are untidy. Dead branches should be cleared. Saplings are in the way. Leaves are covering the ground.
But a woodland is not a garden bed.
Somewhere amongst all of that apparent mess is the next generation of the wood.
Seedlings need somewhere to establish. Young trees have to survive underneath the older canopy until light becomes available. Leaf litter breaks down. Deadwood softens and holds moisture. Moss moves across it. Insects use it. Fungi break it down further, and eventually much of what looked like waste becomes part of the soil again.
Killarney's woodland surveys also show what happens when that regeneration is interrupted. Heavy grazing and invasive plants can restrict the field layer and stop young trees from establishing properly.
So when part of a wood looks a little untidy, it may be doing exactly what it is supposed to do.
Wood-sorrel
Wood-sorrel is an easy little plant to miss because it stays close to the ground.
Look for three pale green, heart-shaped leaflets, rather like a delicate clover. In spring there may also be small white flowers marked with fine purple veins.
Then look again later in the evening.
Wood-sorrel folds its leaves back at night. The flowers also close at night and during rain, bowing down until conditions improve.
It is a tiny response to the weather happening underneath everything else.
You may walk through rain trying to get somewhere dry while the plant beside your boot has already folded itself away and dealt with the problem.
Bilberry
Bilberry is a low shrub rather than a herb, and it is common in acidic woodland and heath.
It has small pointed green leaves with finely toothed edges, and later in the year it can carry blue-black berries. Unlike the blueberries you buy in a supermarket, bilberries have reddish-purple flesh inside rather than pale flesh.
They are eaten by all sorts of wildlife, including birds and mammals.
You may know them by another name. Bilberry has accumulated an extraordinary number of local names across Britain and Ireland — blaeberry, whortleberry, whinberry and others — which probably tells us how familiar the plant once was to people who spent much more time gathering food from the landscape than most of us do now.
Great wood-rush
Not everything underneath the canopy is dramatic.
Great wood-rush often appears simply as broad grassy clumps beneath the trees. It is one of the common plants recorded through Killarney's oak woods along with hard fern, wood-sorrel and bilberry.
This is worth including precisely because it is easy to ignore.
Not everything in a wood needs a rare story or an extraordinary use to deserve its place. A large part of a functioning woodland is made up of very ordinary things doing very ordinary jobs.
SOMETHING GROWING ON SOMETHING ELSE
A woodland can grow on top of itself
This is probably my favourite part of wet woodland.
A fallen branch begins to soften and moss grows across it. A fern establishes itself in the moss. A seed lands in a pocket where leaves have gathered and suddenly there is a little sapling growing from somewhere that does not look remotely like soil.
On older trees the same thing can happen above your head.
Killarney's woodland surveys describe oak branches carrying rich growths of mosses, liverworts and lichens. Thick moss on horizontal limbs can support ferns such as polypody, while small holly and rowan saplings have been recorded growing in the angles of lower branches.
Have a look upwards the next time you see an old moss-covered tree.
You may find another little version of the woodland growing on top of it.
DEAD DOESN'T MEAN USELESS
A fallen tree is not finished
A fallen tree can look finished.
Ecologically, it isn't.
Dead and decaying wood gives insects somewhere to live, provides food for fungi and other organisms, holds water and gradually returns nutrients to the woodland floor. In a damp place it also becomes another surface for mosses, liverworts, ferns and eventually seedlings.
You can sometimes see the stages happening at once. One end of a branch still looks recognisably like timber. Further along, the bark has gone. Moss has covered another section, and somewhere in the middle a new plant has begun growing from it.
This is one reason a healthy wood does not need to look completely clean.
There is a difference between maintaining a path so people can use it and tidying every fallen piece of wood out of the woodland.
BEAUTIFUL DOESN'T ALWAYS MEAN IT BELONGS
Rhododendron
Then there is rhododendron.
When it flowers, it is difficult not to admire it. Great banks of pink and purple flowers through a green woodland can look magnificent.
Unfortunately, Rhododendron ponticum is also one of the major threats to native woodland in Killarney.
It was introduced to Ireland as a garden plant and found the mild, wet, acidic conditions of the west extremely agreeable. It can form dense evergreen thickets, casting so much shade that much of the vegetation underneath disappears. In Killarney it has suppressed the woodland herb layer, reduced bryophyte growth and, importantly, prevented new trees from regenerating beneath it.
That last part matters.
If no young trees are able to grow underneath the old ones, eventually there is no woodland to replace them.
So this is one of those slightly uncomfortable examples where something can be beautiful and still be doing considerable damage.
You don't need to pull it up yourself. Management of invasive plants in protected landscapes is a job for people who know what they are doing.
Just recognise it for what it is.
BEFORE YOU STAND UP
Look at one small patch
If you have crouched down to look at something, stay there for another minute.
Look at the patch immediately around you rather than trying to take in the whole wood.
How many different greens are there?
Is everything you thought was moss actually moss?
Is anything growing from the deadwood?
Turn over one fern frond without breaking it and look underneath. Look at the edge of a leaf. Look at the tiny plants growing between the roots of something much larger.
Then stand up and look at the wood again.
It is still the same place.
You have just seen a little more of it.