Rules of growth

Driven by the need for stability, trees in large groups tend to behave in a certain, uniform way when it comes to growth.

An even shape means an even distribution of forces, providing maximum stability. This is why woodland trees grow arrow-straight trunks with neat, ordered fibres. Sitting atop they have symmetrical crowns with strong branches, supported from beneath by evenly-spread roots.

This phenomenon applies almost equally to broadleaves and conifers. The only difference is the angle of top branch growth – upwards in the former and horizontal or downwards in the latter.

Because forces permeate the entire tree, from trunk to crown and roots, any weak spots are exposed and can even completely snap the trunk.

A curved trunk means uneven distribution, meaning extra growth is required to compensate for the weakness. It also leads to darker rings, due to less air.

A forked trunk leads to a double crown, creating stress on the fork point due to opposing forces. In a ‘U’ shape the fork should survive but in a ‘V’ shape it will likely snap at its narrowest point, leaving the tree highly vulnerable.

Rules of growth are a little less strict at a woodland’s edge, where smaller deciduous trees will grow horizontally towards external light. Conifers, on the other hand, only grow vertically (except pines).

When trees on a hillside or mountain slope continue to grow vertically as gravity forces the ground (or snow) beneath them slowly downwards, a drunken forest is formed.

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Image: My Wisconsin Woods