Evergreen trees – such as spruces, pines and firs – have the shape of a pyramid. Why?
Evergreen trees – which are known collectively as conifers – often grow in places that have severe winters. An evergreen tree’s shape does help keep wet, heavy snow off its upper branches.
Conifers also tend to have shallow roots. In other words, they lack long, sturdy tap roots. So they’re subject to being knocked down by wind. Their shape reduces wind resistance and helps keep the tree standing upright. What’s more, the trees are mostly needle-leaved or scale-leaved, instead of having broad, flat leaves. The shape of the leaves is also an advantage in climates that sometimes feature abrasive, blowing ice crystals.
The tree’s shape also lets it get more light, because the top branches don’t shade the bottom ones. The major branches of conifers are layered, with an open area between the layers. This helps wind pass through, and it helps the tree get enough light, especially when sunlight comes in at a low angle, as it does during the winter months.
Those who admire the shape of a Christmas tree might like to know that its shape has evolved in response to wind, snow, and light.