Ask people what they remember most about the physical surroundings of their childhood and they're likely to describe a special place out of doors--a school yard, a patch of woods, a community garden. For it is outside space that is most conducive to the ebb and flow of spontaneous activities, offers rich and often surprising sensory input, and provides endless possibilities for exploration. If the classroom is the place where children are taught, the outdoors is where they learn on their own.

A growing legion of landscape architects is exploring and exploiting the ability to...