Green Home – Landscaping and Plantings
Many OF THE LANDSCAPING DETAILS around a new home will already be determined by the time construction begins — exactly where the house is, how it relates to existing vegetation, how steep the slopes are around the house, and so forth. In this article, we address how to protect your site during construction and some of the ways you can landscape and manage your site after the house is completed.
PROTECTION OF SOILS AND VEGETATION DURING SITE WORK
The process of building a house can be very damaging to the immediate environment. Typically, a large swath of land is cleared of all trees and shrubs, and the land is leveled. This makes the process of excavation easier, but you lose the potential for nearby trees to shade the house from summer sun, and topsoil that took hundreds of years to produce may be bulldozed under sterile subsoil. The land is prone to erosion, and the stripped soils are prone to revegetation by non-native, invasive plants.
There is a better way. By carefully controlling the house excavation and site work, it is possible not only to minimize damage to the immediate environment, but also to ensure that your property will be capable of supporting a rich, healthy natural ecosystem.
Pay special attention to trees: Saving trees is not only good for the environment; it’s worth a lot of money! Studies show that a single large tree can add as much as $10,000 to the value of a new home, and planting new trees can easily run into thousands of dollars. Be aware, however, that construction activities may destabilize trees close to the house. You certainly don’t want a tree to fall on your home, so it may be necessary to remove some nearby trees.
If there are existing shade trees on the east, west, or south sides of the site, protect them, as they can help lower air conditioning bills by shading the house from the summer sun. On the west and north (where the prevailing winter winds typically come from), trees can help maintain a buffer to shield your house from winds, helping keep energy bills down.
Inventory the site Before beginning site work for a house, survey what’s on the site (trees, shrubs, wetland areas, etc.) and decide how to protect it. If possible, hire an arborist or landscape designer to help determine which trees to protect. If clearing a large area but saving only a few trees, choosing which trees to keep is especially important—the biggest, tallest trees may not be the ones that will be most likely to survive the thinning.
In houses relying on passive solar heating to a significant extent, it’s best to avoid trees altogether on the south side — even deciduous trees, whose trunks and branches still block as much as 50% of the light after the leaves are gone. If you plant trees on the south, choose deciduous trees that will grow tall with few lower branches. If the branches are mostly above the roof plane, there will be relatively little wintertime shading, yet the house will be shaded from the summer sun, which rises high overhead.
In warm climates, the need for air conditioning can also sometimes be reduced by channeling summer breezes through a house. To aid in this, it may be possible to plant hedgerows that funnel breezes from the west, the direction the prevailing winds are from in most of North America.
In cold climates, you may be able to achieve some energy savings by planting evergreens and densely growing shrubs on the north and west to block winds. As we’ve learned to build houses that are more airtight, though, this benefit is not as great as it was in our grandparents’ day, when shielding from cold winter winds was a very important design priority.
LANDSCAPING FOR BIODIVERSITY
As our countryside becomes ever more developed and as ecosystems become ever more degraded, providing diverse ecosystems and wildlife habitat in our backyards becomes more and more important. In many cities and suburbs today, small patches of native ecosystem provide vital habitat for songbirds, butterflies, and wildflowers. If carefully planned, our backyards can serve this function. Even more importantly, if we string together patches of native habitat, we can provide corridors through which wildlife can pass to help maintain biodiversity.
The first priority in boosting your backyard biodiversity is to consider alternatives to conventional lawns. Conventional lawns are biologically barren monocultures of grass species native to Europe (usually “Kentucky” bluegrass, even though the origin of this grass has nothing to do with the state of Kentucky).
Conventional lawns carry several other significant environmental burdens. They require heavy fertilizer applications; they may be treated with herbicides to get rid of broad-leaved plants such as dandelions, or with pesticides to eliminate insects; and they often require watering. They also require frequent mowing, and typical gasoline mowers generate large amounts of air pollution. Lawn mowers have not been regulated until recently, and using an older two-cycle mower (the kind that runs on a mixture of gasoline and oil) for a couple of hours can produce as much non-carbon-dioxide air pollution as driving a modern car halfway across the country. For a green home, it makes sense to minimize lawn area.
If a lawn is a must, try to restrict the size of the lawn, and/or plant native grasses. Buffalo grass is a good choice for dry, sunny areas; it is drought-tolerant, and will only grow about six inches tall if left unmowed. For wetter regions and shady areas, native fescues can be planted. Buffalo grass and native fescues are available from specialty suppliers of native plants.
In place of a conventional lawn, consider planting regionally appropriate, native vegetation. For relatively open, sunny areas, especially in drier regions, prairie vegetation can be established. Tall-grass prairies are native to most of the US Midwest and as far east as Ohio; short-grass prairies are native to drier areas further west. In cooler, shadier areas, native fescues, ferns, mosses, and wildflowers can be established.
Establishing a Prairie
Establishing a prairie may involve removing the non-native grasses, a labor-intensive process of hand-digging the sod. Selective use of herbicides can help in the removal of non-native vegetation, although herbicide use is best kept to a minimum. Prairie plants can be established by broadcast seeding of regionally appropriate prairie seed mixes (available from native plant nurseries or mail-order suppliers) or by planting seedling plugs. Often a mix of broadcast seeding and individual plantings makes the most sense. It will take several years for a prairie to become established, during which time some weeding of invasive plants (dandelions, thistles, etc.) is needed.
Once established, prairie plantings do not require fertilizers, watering, herbicide applications, or frequent mowing. To keep shrubs and trees from gradually taking over, however, annual mowing or burning may be required.
Annual controlled burning is the best way to maintain an area of prairie, even though it is potentially dangerous. Prior to European settlement in North America, periodic fires kept millions of square miles of land open prairie. Fires were started either by lightning or Native Americans. Burning will kill many non-native invasive species, while not harming — and actually benefiting — prairie-adapted plants. Controlled burns do generate air pollution, but if burns are done in the late summer or fall, when the vegetation is dry, these fires burn hot and fast, creating relatively little air pollution. Before carrying out any controlled burn, check with your local municipality to find out about burning restrictions and permits.
Woodlands provide an alternative to lawns in much of North America, particularly the eastern third of the country and the West Coast. There are so many beautiful native trees and shrubs to choose from that exotic species usually aren’t needed.
In selecting trees and shrubs, consider those that provide food and shelter for songbirds and other wildlife (although near your front and back doors, you should avoid plantings that will drop berries or other fruit that could be tracked into the house). By planting vegetation that supports wildlife, you will be rewarded not only by the plantings themselves, but also by the wildlife that will be attracted. From an ecological standpoint, these pockets of wildlife forage are very important, especially in our more built-up areas.
If there are already woodlands around your house site, they may be degraded. If possible, have a landscape designer or arborist with knowledge of native plantings walk your land with you. Look into how you can restore these areas to the healthier, more diverse ecosystems that once existed there. This may involve removing invasive vines and shrubs, opening up some areas (e.g. cutting down trees to provide clearings), and planting of native vegetation.
Native trees, shrubs, and wildflowers can be found in nurseries specializing in native plants. When buying these plants, make sure that they were not dug from the wild; some areas (even National Parks) are being denuded of rare wildflowers by irresponsible nurseries. Ask the nursery to provide proof that the plants you are considering were nursery-propagated and not taken from the wild. If the nursery is unable or unwilling to do this, take your business elsewhere.
The only exception to the rule of not digging plants from the wild is the practice of salvaging native plants from areas being developed. You can certainly dig up wildflowers, shrubs, and young trees from areas of your own property that will be excavated for the house or cleared for a driveway. You may also find salvage opportunities in nearby developments or road construction projects. Always ask permission before digging in such areas, but you are likely to find little resistance if you explain your interests. A few native plant nurseries even specialize in salvage.
A green home should use water very efficiently, both inside and out. In drier parts of the country, in areas where droughts are common, and in municipalities where water supply is limited, water-conserving landscaping is particularly important.
As you think about various landscaping strategies around your house, consider how you might use your landscape for food production. Most of our fruits and vegetables are produced hundreds, or even thousands, of miles from where we live. They are grown using huge quantities of fertilizers and pesticides, then shipped across the country by truck. Or even worse, they are grown in other countries (often developing countries with few safeguards on pesticide use), and then flown to our markets. Any food we can grow ourselves, especially if we grow it organically, will help to reduce the environmental impacts of our food industry.
In designing the landscape around your home, try to provide space for a home vegetable garden. In choosing trees and shrubs, consider those that will produce food for your family. Permanent plantings for food production are aspects of a practice known as permaculture. Ask at local nurseries about appropriate plantings. Depending on where you live, consider apple, peach, plum, cherry, citrus, avocado, raspberry, blueberry, kiwi, and a wide range of nuts (walnut, chestnut, pecan, filbert, etc.). While some of these are not native plants, most will not become invasive (taking over natural vegetation), and their benefits in food production justify their use.
The landscape around your house is the first thing visitors will see; it’s also what will greet you when you arrive home from work or look out your window on a Saturday morning. The perfect complement to a green home is a landscape that supports the region’s natural biodiversity, that requires little, if any, irrigation or fertilizing, that requires a minimum of mowing, that keeps rainwater on the site and able to soak into the ground, that helps reduce energy use in your home, and that even provides for some locally grown fruits and vegetables. All this can be achieved with a little planning and care. And once established, an environmentally responsible landscape should cost less to maintain than a conventional landscape of lawn and shrubs.