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.

209Copying

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.

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