Landscaping for peace and quiet may sound impossible, but there actually are ways to use plants and earth to block sounds.
Plants can be used as sound insulation, but they have to be thick. To block unwanted traffic sounds from your house, plant hedges, bushes, and trees on the side toward the road. Hedges should be at least two feet thick.
Earth can also be used, if you have the space. Create small mounds (berms) between your house and the source of the noise. For further sound absorption, cover the mound with a dense hedge.
A windbreak is useful if your house is downwind from a factory or school yard. A dense evergreen or hedge will provide protection as far downwind as 20 times its height. So, a 9-foot-tall hedge can be planted as far as 180 feet from your house and still offer protection from wind-borne noise.
A wall or tight fence covered with dense vines will absorb some sound. An uncovered wall, though, will only make the noise problem worse.