“When she saw the lilac we had to cross the street and take the wheelchair right up to the bush for her to really smell the fragrance. It was very important to her. To feel the flowers, to somehow come close.” ―Nursing home staffer
Touching intensifies awareness. Physical contact is so much more visceral than simple viewing that even when things are not touched but merely placed within touchable range, they generate a greater psychological impact than things placed out of reach. Neuropsychological research confirms this by showing that information from touchably close objects is processed in a different part of the brain than more distant items, so “it is hardly surprising,” the Kaplans conclude in With People in Mind, “that a wide trail that puts one physically more distant from nature increases the psychological distance as well.”
They add, “The width of the trail affects the intimacy of the experience.” As a result, it makes sense for designers to position strolling paths to oblige walkers to brush up against tree bark, shrub leaves, and rough stones, fences and walls.
Intimacy takes on a special meaning when it involves another person. Touching, the essence of intimacy and the first sense we are born with, is the final sense we engage when meeting someone else. A handshake or caress can only occur within a half meter/1.5 feet, so that distance forms the limit of the realm of intimacy.
An adult’s hand dropped down by the side is about 0.6 m/2 feet from the ground, so plants bordering the treadway must be at least that high to be readily touchable. They must be at least 0.3 m/1 foot high to be reachable from a wheelchair, while 0.6 m/2 feet is preferable there, too.
Meanwhile, adults extending their hands out to the side reach about 75 cm /30 inches from the side of their bodies. Since walkers typically avoid the outermost 15 cm/6 inches of treadway, an arm extends at most about 0.6m/2 feet beyond a path edge. Thus, for contact, a path’s border must be within 0.6 m/2 feet of the path’s edge, and at that distance, needs a height of about 1.5 m/5 feet.
Normally, however, our arms tend to swing forward and back while walking, not to the side at all, so the best position for touchable plants is lapping over the walkway’s edge, intruding on the corridor. This may be why we prefer paths that meander like a stream among shrubs and perennials occasionally draping onto the treadway.