The flag effect with trees can be confused with the tick effect but nonetheless can be a really useful natural navigation technique to determine direction and is relatively straightforward.
The flag effect is where a tree’s growth is effected by the prevailing wind. Often in the British Isles the prevailing wind comes from the south west so in the photo below (taken on the South Downs) the branches on the left hand side are much longer indicating north east.
Be aware, however, that whilst the prevailing wind in the British Isles is generally from the south west, it isn’t always. Where I live on the north coast of Kent we often get strong winds from the north and so the flag effect indicates south! Local knowledge is key for this technique.
We cover natural navigation, including the flag effect with trees on our  IOL Bushcraft Competency course.
You can see plenty of photos from these courses, as well as all of our others, on our Facebook page.
