Wind
A strong movement in the crown will produce more growth, for the reason that the tree will transpire more - its excessive transpiration will require more water - which it will take up, not just water, but also nutrition from the soil. You get fast growth on a day when the tree is moving about.
But we don’t want the tree to move excessively - so we try to encourage an understorey which deepens the length of the tree and slows down the wind. So now the tree crown moves about gently - because the understorey is like another crown layer further down - we don’t get a tapering stem and instead, get a cylindrical shape, which is more valuable.
Spacing
This is essential, so you have no option but to leave some poor trees against the movement of wind. Look at these good trees - the light intensity can reach all the way down and all the way round. Always grow your stand for an "opportunist market" - do not fix a felling year for it - wait for a buyer to come along with high quality needs.
Beech
Is planted to side-shade the oaks (equally important as to produce timber themselves), so if you have a stand of reasonably good oak, and if you’ve got room, then underplant with either Beech or Hornbeam - to keep their side-shade on the stems.
Poor Sycamore
This stand shows lack of proper thinning - giving height at the expense of diameter - too late to thin now - it is past its optimum diameter.
It needed earlier and more regular thinning - we’d have a larger crown size and consequent increase in diameter - far better. Sycamore, being a light demanding species, needs not just a full crown, but a crown which is virtually all accessible to the sun.
Assimilation comes off as you come down the crown. If you haven’t got the depth or light intensity round it, then the crown is not working to its full capability.
"Assimilation" means the tree’s ability to absorb sunlight for the production of foodstuff to extend the stem. If you get dense shade, the ability to assimilate drops off with a light demanding tree - so it is not utilising itself to the full.
Quality Sycamore
Here we have liberated the crowns over three thinnings and tried to keep each crown about 50% of its length. The distance between trees is judged carefully to give a cylindrical stem over the first length.
Larch
It is retained here to encourage the broadleaves to get the length. We must reduce the windspeed in the crown of the tree - this is critical - so Larch is grown with the broadleaves for this reason.
Always try to develop a large crown - that’s not sufficient alone - as much of the crown needs sunlight - because the assimilation falls off as you come down the crown, balancing the depth and size of the crown so that it is fully operational - at the same time you don’t want too much movement - causing buttressing at the base (you don’t want a tapered stem, you want a cylinder). Some movement is alright, but not excessive, or the tree will have excess buttressing.
Ash
"The greedy tree" - quality ash is best grown as individuals - their huge crowns cause nearby trees to lean backwards and spoil. Ash needs too much room and its suckers utilise too much nutrient.
Keith Rawling (left) and Lewis Scott at our Field Day.