When looking to save energy at home, most people understandably focus on the inside of their house. But we should also look outside, since landscaping decisions can make a big difference in how much energy is used. Environmentally sound landscape design not only reduces the amount of electricity and gasoline needed for power equipment, but also helps maintain a comfortable temperature inside the house. The following are ideas on how to use groundcovers, trees, and shrubs, as well as landscape techniques, to reduce energy consumption.
Covering the Ground
To many people, a yard signifies an expanse of lawn. But a lawn can unfortunately have considerable environmental impacts when it is maintained using synthetic fertilizers, herbicides to control weeds, pesticides to control insects, and copious amounts of water. Lawn mowing causes considerable air pollution since most mowers have few pollution controls. A five-horsepower gasoline mower can emit as much air pollution as a 200-horsepower car.
A good way to reduce the environmental impacts of lawns is to limit them to areas where they will grow best, i.e. where there is adequate sun and the ground is fairly level. In less than ideal areas, you can reduce the size of the lawn by planting shrub/perennial beds around or within it. Use other groundcovers on slopes and in shadier areas where grass does not grow well. Many groundcovers require minimal upkeep. Plant sunny areas and slopes with drought-resistant perennials and shrubs such as daylilies, sedums, prostrate junipers, and low-growing ornamental grasses. Vinca (creeping myrtle), pachysandra, and liriope are reliable choices for shady locations.
In those places where you plant grass, you can minimize its long-term maintenance needs by getting your new lawn off to a good start. The single most important thing to do is to plant a mixture of quality grass seed (compatible with the soil and amount of sun for the area) over a 6" base of topsoil amended with organic matter such as leafmold or dried manure. The organic matter increases the water-holding capacity of the soil. The generous amount of topsoil allows the grass to develop deep, strong roots which better withstand dry conditions, thereby reducing water consumption. A lawn with a strong root system is healthier overall; its thicker growth makes it less susceptible to weed and insect problems.
Energy is also consumed by using weed wackers to trim grass edges. This trimming can be minimized, if not eliminated, at the outset by installing edging material around planting beds, structures, and trees in the lawn area. An edge of 1' x 3' flagstone, flat rocks or bricks laid lengthwise provides a mowing strip for the lawnmower wheel to pass over. Another alternative is to apply mulch in a generous circle (3' minimum) around trees in the lawn area to reduce the necessity of trimming.
Using Trees and Shrubs to Modify Exposure
What you plant outside a building can determine the temperature inside the building. Plants can intercept exposure to strong wind and sun. Because of their size, trees are the most effective plants for this purpose. Exposure to sun is greatest to the south and southwest resulting in greater variability in temperature. Exposure to winds is greatest to the northwest.
To create a more moderate microclimate, use deciduous trees to intercept the sun and evergreens to screen the wind. Large deciduous trees planted at least 15' to 25' away from a house on the south and west sides will provide afternoon summer shade (while still allowing cooling winds to pass through the tree canopy) yet permit sun to pass through bare branches for solar gain in winter. In addition, you can reduce cooling costs by making sure that air conditioning units are shaded.
Because it takes so long for deciduous hardwood trees to mature, plant them first. Avoid varieties which grow fast since their wood is weak and susceptible to storm damage. Instead, select hardwoods such as maples and oaks that are disease and pest-resistant. For less leaf clean-up, plant trees with smaller leaves such as Thornless Honeylocust.
Large evergreen trees or a hedge of tall evergreens are effective windbreaks on the west/northwest side of a property. The amount of protection afforded on the side protected by the wind (the leeward side) depends on the height and length of the plants used. You should avoid building an impenetrable windbreak, since that create a strong vacuum on the leeward side, but trees will permit enough wind to pass through to avoid this problem. Suitable evergreen trees for windbreaks include White Pine, Blue spruce, Norway Spruce, Arborvitae, and American Holly.
A foundation planting of shrubs can also be helpful. A solid wall of evergreen shrubs located at least 4' to 5' off the house creates an area of relatively still airspace between it and the outside walls of a house. The still air has less cooling power than moving air which increases loss of heat through the walls in winter. It is important, however, to choose slower-growing shrubs and locate them where they will not block solar gain through windows. In addition, by selecting slow-growing, compact shrubs, less pruning will be necessary.
When planting beds are used instead of lawns, they can provide localized protection from wind. These can be deep areas (10' or more) which accommodate a mix of deciduous and evergreen shrubs and groundcovers. As with lawns, you should first prepare and amend the soil with organic matter to encourage optimum growth. Mulch such as wood chips or pine needles will keep soil temperatures more even and reduce weeds. When watering to establish or otherwise maintain the beds, avoid overhead sprinklers because much of the water evaporates in the air. Instead, use drip irrigation and soaker hoses which are more efficient.
There are many ways to create an environmentally friendly landscape, but the greatest opportunities are presented when a new home is constructed and its surrounding property first developed. Initial landscaping efforts have an impact for years to come. Wise decisions regarding siting of shade trees, locating and creating planting beds and lawn areas, and improving the existing soil translate into long-term savings of natural resources and dollars. Once established, an additional reward of the environmentally friendly landscape is its ease of maintenance.
**This article, Landscaping to Conserve Energy, appeared in the Spring 2001 issue of NESEA’s magazine, the Northeast Sun. It was written by Jan Godek, a garden designer in Long Valley, New Jersey and a member of the Washington Township Shade Tree Committee. She specializes in shrub and perennial beds and borders for residential and public landscapes.
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