The Natural Garden was created to be an environment that encourages visitors to rest, relax, and reflect on the very essence and brevity of life. This garden in its current configuration is the most recent addition to the Portland Japanese Garden, and it is also the most contemporary style, referred to as zoki no niwa, a style which includes plant materials that fall outside the list of plants traditionally associated with Japanese gardens. Notable is the use of vine maple, a shrub indigenous to this region. The garden focuses primarily on deciduous plants and is laid out to present seasonal change, from the budding new leaves of spring to the coolness of summer shade, the changing colors of autumn to the naked trees of winter. Originally called the Hillside Garden, referring to the steeper terrain in this part of the Garden, the denseness of the trees and shrubs create an immediate difference in atmosphere, something wilder yet equally tranquil. The flow of energy (ki) through the garden refreshes and restores all those who walk there. While the flow of ki is primarily directed by the waterway, note that nearly all the deciduous trees lean slightly in the same direction that the water is flowing. This garden was originally planned by the Garden's designer, Professor Takuma Tono, as a moss garden, but the plants proved difficult to maintain. The garden was redesigned in the early 1970s and then again in 1990, due to damage from earth movement.