Although the effects of a garden on the senses of touch, smell, and sight are often very subtle and difficult to define, they are elemental to an appreciation of the setting.
Light and Shadow
The quality of light and shadow varies according to the sun’s orientation to a site and the ability of the light to reach the ground. The amount of light a particular location receives during the course of a single day will greatly influence how the landscape should be designed. For a site that is too enclosed by tall trees, consider ways of allowing more filtered light. Observe the interplay of light and shadow: Size and temperature can be increased or decreased, and complexities of line and texture can be highlighted or deemphasized.
Illumination that strikes surfaces can be described as front, side, and back light. Front-lighting can reflect onto and brighten dark surfaces. Sidelighting heightens contrast and can produce silhouettes. The most dramatic backlighting occurs twice a day, when the sun rises and when it sets. Another example of backlighting is when the rays of the sun fall through a canopy of leaves. Backlighting is a popular technique used to illuminate a garden at night: Hidden lights cast a diffused glow behind foliage or objects of interest.
Also pay attention to shadow patterns caused by the house and trees. They can influence decisions about the positioning of sitting areas and the choices of construction materials and plants.
Sound can be conducted or carried depending on the needs of the situation. The splashing of a nearby stream or the rustling of a large tree, for example, may be highlighted by allowing an unobstructed flow of air from the stream or tree. Street noise, on the other hand, may be muffled by building solid fences or walls that will block the movement of sound. Unpleasant sounds can sometimes be masked with more musical ones.
When air moves over cool land it is cooled and flows downhill, from high to low elevations. Fog, a dramatic example of this process, can be seen flowing down mountainsides and collecting in valleys. Cool night air collects in low areas — frost pockets. It may also become trapped by an obstacle to its downward flow, such as a house, making the uphill side of the house cooler in the evening than the downhill side.
Correspondingly, warm air moves upward, from low to high elevations. To help an area retain warmth, provide surfaces that absorb heat during the day and release it at night. The heat of the sun can be best exploited by tilting surfaces at an angle perpendicular to the sun. A wall angled to collect direct sunlight will be warmer than an adjacent vertical wall. Solar panels are positioned to take advantage of this fact. Absorbed and reflected heat can noticeably warm the area surrounding the heat-retaining surface.
In choosing building materials for structures in a garden, take into account how much heat they retain. Stone, for example, retains much heat; wood retains heat moderately well; and fiberglass retains very little heat. Heat absorption is affected by other factors, as well. Dark materials absorb more heat than light-colored ones. Most natural materials absorb heat well.
Because color is a phenomenon of light, both the intensity of sunlight and the quality of shadow affect the reflectivity of color in a garden. On an overcast day, colors appear muted; on a bright, summer day, they seem vivid. These changes may affect mood, perhaps unconsciously: People feel depressed on a gray day and vivacious on a sunny one.
Colors also alter perspective. Light, cool colors enlarge space; dark, warm colors make areas appear smaller. Blue and gray seem farther away than dark green and red.
The nose, like the ears and eyes, is one way to perceive the landscape. If a site is affected by unpleasant odors, such as exhaust fumes from a busy street or the smell from a chicken coop, locate major activity areas upwind from them, if possible. Ephemeral scents, such as those of certain vines, shrubs, and trees, can help to camouflage offensive smells as well as add force to the landscape.
Plan to place the most fragrant plants where they will do the most good. For instance, plant night-blooming nicotiana around a hot tub that is used at night, and honeysuckle by the front gate.
Fine textures such as lawns, mosses, and large, smooth pavements tend to accentuate the mass and shape of the ground and to increase its apparent size. These areas often act as a neutral screen or background for other textural elements placed on them — furnishings, sculpture, and even people.
Coarse textures such as cobbles, bricks, tufted grasses, herringbone decking, and redwood blocks or rounds draw attention to their surfaces. For this reason, consider the range of textures to use in order to downplay or highlight the topography.
In planning textures, as in planning all other design elements, be clear in your intentions. Use coarse or fine textures and materials of strong color definition sparingly and dynamically. Avoid mixing too many textures in a single pavement area, but do allow special, intricate textures to stand out, or create areas with textural contrasts. Remember that fine-textured plants lose their distinctive quality if planted in the distant background. Similarly, coarse-textured plants may be too bold for close-up viewing. For the best effect, place plants where their textural qualities will be spotlighted.
An area in a patio intended for barbecuing might be surfaced with smooth concrete, which is easy to clean, and the remainder of the patio could have an exposed aggregate surface that reflects less light and is more visually elegant in keeping with its use as an outdoor living room.
A microclimate is the fairly uniform climate in a locality or site. It may also be a pocket of modified climate within one site. Temperature, relative humidity, and wind determine climate.
The importance of the microclimate cannot be overemphasized. In planning where to plant a shrub that requires full sun, where to build a deck, and even where to place major walkways, the nature of the microclimate will determine the success of a design.
The microclimate of a landscape is influenced by four factors: the presence or absence of direct sunlight, the temperature of the still air, the relative humidity, and the amount of wind. The outdoor comfort range generally lies between 70 degrees and 80 degrees, as long as the relative humidity is between 20 and 50 percent, and the wind less than 3-1/2 miles per hour.
The higher the humidity rises, the more unpleasant high temperatures become. Wind can reduce the effects of humid weather; however, where wind velocity exceeds about 3-1/2 miles per hour, comfort diminishes. In a hot, humid climate, look for ways to provide areas that are shaded from the sun or ways to make the most of cooling breezes.
Strikingly different directions and velocities of wind occur at different elevations. The wind speed at 1 foot above the ground may be only half that at 6 feet above the ground. When the wind is obstructed, it will slow down even further. Even a 2-foot-high barrier can block most ground wind, a feature to keep in mind when planning a deck or patio in a windy location.