By Dean Nernberg
One of the most important factors in successful native plant gardening (or any gardening, for that matter) is site preparation; in fact, it should account for at least 90 per cent of the time and effort you spend establishing your garden. If done correctly, future maintenance requirements will be greatly reduced, while your enjoyment of the garden will greatly increase. You can also add diversity to your landscape by modifying some of the conditions described above. The main aspects of site preparation are outlined below.
Removal of the existing vegetation
Unless your garden is already perfectly clean, you will need to remove the vegetation that is already growing there (e.g. grass, weeds, etc.). This can be accomplished by pulling (for annual and easy-to-remove weeds) or digging (for perennial grasses and weeds with extensive root systems or deep taproots). Alternately, small areas could be covered with black plastic for at least one year. With the lack of sun and steam-heat produced under the plastic, any existing vegetation and weeds should be killed. The use of herbicide is usually not necessary in small areas, but may be a last resort for large spaces in order to eliminate aggressive species.
If the soil in your yard is heavy clay or very sandy, it would be beneficial to amend it by adding rich organic loam. If it is very heavy clay, you should remove at least 150 to 300 mm (6 to 12 in.) of the soil surface and replace it completely with organic loam, such as commercial garden soil. Sand can be added to increase drainage, if that is a problem.
Some relief or elevation changes in the garden—such as mounds, slopes, raised beds and terraces—can produce added interest and more varied planting options. A garden or flowering bed that is raised or higher than the surrounding area will always perform better, as the soil will warm up faster and have better drainage. However, be sure any grades or slopes you create drain away from your house to prevent water from reaching the foundation and possibly seeping into the basement.
Edging or barriers
If your garden is adjacent to a lawn or grassy area, consider installing some form of edging or barrier to prevent grasses from spreading into and taking over your garden. The edging should be at least 152 mm (6 in.) deep; leave at least 6.4 to 12.7 mm (0.25 to 0.5 in.) above ground to prevent grass from creeping over the edging. When connecting separate lengths of edging, be certain to overlap them by at least 76 to 152 mm (3 to 6 in.) to prevent grass from getting past the break. To make cutting the lawn along the edging easier, install bricks or paving stones along the garden side to allow the wheels of the lawn mower to ride on the bricks.
This is 3 of 5 in A Guide to Gardening with Native Plants