Most people are familiar with the shoot systems of trees but few people know much about their root systems; fewer still know much about how the architecture of trees helps them stand up against the major natural force threatening to topple them: the wind.

Trees typically have a single woody trunk that projects many meters vertically from the ground. Only toward the top of the tree does repeated branching form ever-narrower branches and twigs, which together make up the compact crown where most of the leaves are held.

It is a commonly held fallacy that the root systems of trees belowground are mirror images of the shoot systems aboveground. The roots do branch, and they extend radially about the same distance from the trunk as the crown, but here the resemblance ends. There is no belowground equivalent of the trunk because the central tap roots of...