Archive for August, 2014

Planting Trees: Layout

Written by patrickw on . Posted in Uncategorized

Having found a suitable site for planting a new woodland and decided what kind of trees to plant, the next step is to consider the layout. There are various decisions to be made – whether to plant in straight lines, curved lines or at random; whether to include glades, rides and ponds etc – but the most important consideration is how far apart to plant the trees.
    Government grants have been paid on new woodland planted as wide as 3m apart, and even when grants are not available there’s a great financial incentive to plant on a wide spacing. Planting at 3x3m requires 1100 trees per hectare but changing to 2x2m more than doubles the number of trees to 2500. Each extra tree means another tree protector and mulch mat, both of which can cost more than the tree seedling, plus the time it takes to plant them. The temptation to go for the wider spacing is clear but it’s best resisted because if they’re too far apart the trees will never be usable for timber, and not much use for coppice either.

The Woodland Cycle
Woodland trees are planted close together, typically at 1.8×1.8m for broadleaves and 2x2m for conifers, though this does vary according to species. As they grow they’re progressively thinned until the final stand may contain as little as a tenth the number of trees that were initially planted. This ensures that the trees are always at the right distance from each other for their size. They grow up straight, seeking the sun above and their lower branches are shaded out by their neigbours. This way you end up with straight, branch-free timber which can be sawn up into planks, beams and other useful items.

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These beech trees have been planted at the right spacing and progressively thinned to give a fine stand of high quality timber.

    Trees planted too far apart grow up crooked and branchy. They can’t be used for timber and are very difficult to process for firewood. If the trees are grown as coppice rather than timber a wider spacing may give an adequete yield but the poles will be too branchy for craft use.  Branchiness is less important for fuelwood but it’s still easier to handle wood if it’s straight – and much easier to split it.The yield of the plantation will be lower at a wider spacing too.

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This oak, though a fine tree in many ways, has grown without close neighbours and will not make good timber.

    The cycle of growth in a tree plantation is very similar to that of a natural woodland, where seedlings come up thickly, often thousands of them in the space that will eventually be occupied by one tree. Ash seedlings are particularly prolific and you may have seen them come up like a carpet under a mother tree. Throughout their growth the young trees compete with each other and the vast majority die before they reach the canopy. Where natural regeneration happens on previously unwooded ground a common pattern is for the first generation of trees to grow up as isolated individuals, followed by the usual dense mass of seedlings in the second.

Planting for the Future  
We always plant trees for future genenerations. Trees are so long lived that the person who plants them rarely sees them mature. So we need to bear in mind the needs of people who will live perhaps 100 years after we’re gone.

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These trees have been planted much too far apart and will never yield a usable crop.

    These days some people plant at a wide spacing, thinking only of the ecological, wildlife and visual outputs of tree planting, and saving themselves a bit of money at the same time. We can afford to ignore useful outputs in this way, cushioned as we are by an abundance of cheap fossil fuels. But future generations won’t have the same access to steel girders and heating gas that we do and will be glad of a supply of beams and firewood. The ecological benefits of tree planting are much the same however far apart we plant the trees. But if we plant them too far apart we deny future generations the renewable resources which they will need.

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That’s more like it!  Pentiddy Community Woodland, Cornwall.

    If you can’t afford to plant at the correct spacing I suggest you consider planting a smaller area or spread the planting over two of more years.

Planting Trees: Which Species?

Written by patrickw on . Posted in Uncategorized

Having located a suitable piece of land for planting a new woodland (see my previous post) the next thing to decide is what species of trees to plant. The two big influences on the choice are the nature of the site and your reasons for planting.

Site
Planting woodland trees is a very different matter to planting orchard trees or vegetable crops. Fruit and vegetables are just about the highest value crops we can plant and we’re richly repaid by putting a lot of effort into both preparing the site before planting and intensive care thereafter. The output of woodland trees, though important is nowhere near as great and doesn’t justify improving the soil and planting windbreaks before starting or to giving the ongoing care and attention that we lavish on gardens and orchards.
    Woodland trees may get a little attention in the first couple of years but after that they’re on their own. This means it’s of utmost importance to match the species of tree as closely as possible to the site conditions: soil, climate and microclimate. If we get it right the trees can look forward to a long, healthy life and future generations people can get a reliable harvest of timber and wood. If not, the trees will struggle and the people will be disappointed.
    The great woodland expert, Oliver Rackham, once said, “I remember a landownder telling me his father had planted pine on a field and he’d just harvested a good crop of ash off it.” In other words, the crop tree was chosen so badly that it was taken over and suppressed by another species which self-seeded from nearby parents.

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These self-seeded birch have completely suppressed the planted trees in the plastic tubes.

Multiple Outputs
Hardly any of us plant trees with a single aim in view. Production of timber, ie tall single-stemmed trees which can be sawn up into planks, or of wood, ie coppice trees which can yield firewood and craft materials, are both compatible with creating widlife habitat, improving the soil and microclimate and enhancing the landscape.
    Often different parts of the wood provide different outputs. The woodland edge, for example, is not a good place to grow timber, as the trees there will have a branchy form which will be no use for sawing up into planks. But it is the ideal place to plant trees and shrubs which produce flowers and fruit for insects and birds. Even a few of the hardiest fruit and nut trees for human consumption, such as damsons and sweet chestnut, can be grown there.

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The woodland edge is a place of great biodiversity.

Native or Exotic?
I used to be a passionate advocate of native trees. Even as a child the sight of a sycamore wood used to make me shudder a little. Of course I didn’t know that it was an exotic, ie non-native, species, one which supports a tiny amount of biodiversity compared to our beloved native oaks. But the more I learnt about ecology the more it reinforced my early intuition. As a permaculture teacher I adopted the maxim: “If I can achieve my aims with native species I’ll always use them. I’ll only consider using conifers for something which natives can’t do.”
    But now we live in a different world, a world of climate change, and this has turned my ideas on their head. Trees are very long lived plants. Oaks and beech, for example, take 100-150 years to grow to maturity. Although we can’t predict just what the climate will be like as they mature we can be sure that it will be different from now. Looking at the most likely scenario, Martin Crawford, the famous forest garden expert, reckons that in the south of England the so-called English oak, Quercus robor, will be out of its climatic zone within the lifetime of trees planted now. They may succeed if they’re planted on north-facing slopes, but not on other sites. So he recommends planting species and strains of timber trees which currently thrive in south-west France.
    On the other hand, it’s also possible that climate change will so alter the ocean currents in the North Atlantic that it will actually become much colder here in Britain. So what do we do? Well, the chances of it getting warmer are greater than it getting colder but we must plant with every possibility in mind. So I would suggest planting carefully thought-out mixtures containing trees with a wide range of climate tolerances. As the years go by and the direction of climate change becomes more clear, we can take out the less suited species as thinnings and leave the most suited to grow on to maturity. And it’s most likely that those will be exotic species. Hanging on to a strict natives-only policy in the current circumstances would seem to be futile to me
    Diversity is always a good permaculture principle but random mixtures of plants rarely have any advantage over monocultures. An effective polyculture needs to be well thought out, and trees selected along the lines I’ve suggested here should make our future woodlands much more resilient in the face of climate change.

For a guide to choosing tree species and to small-scale tree planting and forestry in general I recommend Tall Trees and Small Woods by William Mutch.

Planting Trees: Choosing Land

Written by patrickw on . Posted in Uncategorized

Planting trees deserves to be done with great care and forethought. Woodland trees live for a very long time and we plant for future generations. We need to be sure that what we leave, to both people and the Earth, is the very best we can. Many things need to be considered in a planting plan but first of all, and perhaps most important of all, is the site. Those of us who don’t have access to our own land may jump at any opportunity to plant on whatever land becomes available, while some people who have their own land often plant trees on part of it simply because it’s surplus to immediate requirements. But turning land over to woodland is a big step and needs to be thought about carefully.

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We all love to plant a tree. Pentiddy Community Woodland, Cornwall.
    
Biodiversity
We often assume that planting trees always represents a gain to biodiversity, but it’s not necessarily so. The vegetation which is already there may have a high degree of diversity, much higher than a new plantation which could replace it.

Herb rich grassland, of which we have lost some 99% in the past half-century or so, is an amazing ecosystem, full of a wide diversity of wildflowers and invertebrate animals, many of them now very rare, which are dependent on the sunny conditions they find there. A new woodland, by contrast, is very poor in species. Once the canopy has closed and the sun-loving creatures have all died out, there’s virtually nothing there but the planted trees. Woodland wildlflowers and invertebrates are very slow to colonise. These days, when remaining ancient woodlands which can provide the colonists are few and far between, it may never happen at all.

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A wildflower meadow: the very last place to plant trees. Butleigh, Somerset.

Tragically, the few remaining scraps of diverse grassland are often the very places which get planted up first. They tend to be in places which for one reason or another are difficult to farm and have thus been left alone. There may even be a few pioneer trees and shrubs there already and this can give the idea that by planting trees there we’re simply following nature’s lead. That may well be but before you make any decisions I do impore you to make a good botanical survey, or ask someone else to do it for you. Your local Wildlife Trust will probably be delighted to do so for a small donation.

 Heathland, scrub and marsh all have their wildlife value and a change from that state to a new plantation usually means a loss of diversity.

Farmland
Most of the surfce of Britain is made up of farmland, including arable and grassland. This works out at something like an acre (o.4ha) per person. At present, with unbridled use of fossil fuels, we import some 40% of the food we eat. But future generations will most likely need every bit of that land to feed themselves. Hopefully this will include a lot of agroforestry, where productive trees are intimately mixed with field crops and grass. But that’s not the same as planting it up with woodland.

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Agroforestry: wheat and walnuts. Middle Claydon, Bedfordshire.

Trees to provide us with timber and fuel are a very important output. In medieval times woodland was sometimes worth more money per acre than arable. But trees are the natural vegetation of this country and can grow almost anywhere, whereas farm crops are more demanding and will only yield well on good land.

Where to Plant
So that leaves land which is neither of high value to wild species nor good farmland. Where can we find it?

Planting new hedgerows, or replanting old ones which have been taken out is an obvious starter. Along with that I would include windbreaks and shelterbelts. They take up very little land and the increase in yield they give to adjacent farmland far outweighs the loss of production due to the land take.

In hilly country the prime place is steep land. It’s hard to farm steep slopes productively, either with crops or animals, and thier output of food is limited. Look around any hilly district and you’ll see a close match between the steepness of slope and the siting of ancient woodland. This doesn’t apply to modern plantations, which are often placed quite irrationally. But beware – steep slopes are often the last refuge of wildflower-rich grassland!

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Some scraps of ancient woodland survive on the steepest slopes in this landscape. Filling the gaps in with new planting could be a good idea.  Near Ffarmers, Mid-Wales.

In flatter parts of the country land which is less suitable for farming includes poorly drained clays and acid sands which are low in plant nutrients. These days soils like these can be forced into productivity by artificial drainage and chemical fertilisers. Our descendents, without the access to fossil fuels and other non-renewable resources that we have, will find it much more difficult to grow crops on them.

It may be frustrating if you’re raring to go and someone offers you an opportunity to plant on a site that isn’t suitable. But before you rush into it, please do give a thought to biodiversity and to our descendents.

Permaculture Design Course on Dartmoor