Trees don’t grow as children draw them—straight trunked, bushy leaves at the top, maybe a couple of branches off in either direction. Instead, they grow with the sun. In the Northern Hemisphere, when the sun is at its highest point, giving out most of its energy, it is due south. Trees here will naturally be thicker and greener on their southern side. If you are ever lost, look for a tree, and you’ll have a ready-made compass point. 

Go closer and you’ll find more clues. While on one side branches grow straight out toward the sun, branches on the opposite side will reach upward, trying to peer over and catch the light. Leaves on either side are different, too. Sun leaves are thicker, paler. Shade leaves are larger, thinner, darker. Then, look for the insects: Trees tend to bend...