How do trees hold themselves up?

If you watch a mature tree on a windy day you will notice that whilst all the outer branches are moving, the centre trunk is still. The tree canopy is defusing the energy of the wind to protect its centre from rocking out of control. A tree with a lot of space around it develops a mature and well developed crown so is better equipped to defuse strong winds whereas trees grown close together rely on each other to do this as alone they are weaker with thinner canopies. In a dense copse, the trees on the outer edge are the strongest as they have grown having to withstand prevailing winds and if they are removed the weaker ones in the middle can soon blow over, deprived of their protectors.

Think of a large tree with an established root system as having the same dynamic as a lovely red wine glass, with a wide bowl supported by a thin stem and wide base. If you put such a glass on a table, without wine, and try and blow it over you won’t be able to. However, put a pencil on its end and you can blow it over no problem. Trees grow with a similar stability. Wide rounded crowns, a slender trunk and a wide shallow root system make them mechanically very strong.

Multi stem trees have a low centre of gravity so are the best equipped to withstand the strongest winds. Feathered trees, i.e. with branches all the way down the trunk, are also stronger than lollypop shaped trees. I never forget walking passed a Pinus nigra Austriaca (Black Pine) on a stormy day on the Norfolk coast, as when I was under its protection the air was completely still with all of the tree’s branches and needles diffusing the strength of the wind.

At Barcham, we grow our large trees at wide spacing to make them strong. If our trees can withstand our fen climate they will be fine when planted in your garden!

Posted by Mike Glover

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