Sorting out the names and uses of all the landscaping materials on the market can be quite time-consuming. In the department of rocks and gravel, two products -- river rock and pea gravel -- stand out for their smoothness and elegance. Choosing between one or the other is a matter of knowing the basic characteristics of each material -- although some landscape projects make use of both materials.
In some ways, the difference between pea gravel and river rock is primarily a question of size. Technically, pea gravel is any washed, screened rock product between 1/8 inch and 3/8 inch in size. River rock is graded by size anywhere between 1 and 12 inches. Both are collected from river beds and have a smooth, polished look to them. Their appearance is a soothing contrast to the other, more jagged and rough-looking stone products available at landscape suppliers.
River rocks and pea gravel are most often found as a multicolored product with significant natural variation, depending on the source. Both products typically come in an array of mixed earth tones. Sometimes river rock can be found in batches of a uniform gray color, which has an understated appearance compared to the more common multicolored river rocks. Pea gravel can be found in batches of many specific colors -- blue, black, white, tan and reddish-orange, for example. Having this color palette to choose from is a big advantage when designing the landscape.
River rock and pea gravel are used decoratively in the landscape as well as for soil stabilization and drainage purposes. One of the classic uses of river rock is the construction of a "dry streambed." These are ornamental drainage features built along the natural path that water takes in a heavy downpour and are typically planted with water-loving species. Pea gravel can be used to fill in the gaps of the larger pieces of river rock for a more natural appearance. Pea gravel also makes a solid and attractive surface for pathways and can even be used in place of regular gravel in parking areas and driveways. Because of its size, river rock is completely inappropriate as a walking or parking surface.
The main thing to remember about installing both river rock and pea gravel is to first lay down a weed barrier. Plastic can be used where plants are not being grown, but a fibrous "weed fabric" lets water through for plants and is more durable in the long run. Plant larger shrubs and trees first and then install the weed barrier in overlapping sheets, securing it with landscape staples. Cut holes in the fabric to plant smaller species and then cover the area with the stone. For paths, 2 inches of pea gravel is sufficient, but use at least 3 or 4 inches for driveways. When installing river rock, use enough to completely cover the weed fabric. One other key difference in installing river rock versus pea gravel is that each of the larger river rocks needs to be intentionally placed, while pea gravel can simply be dumped and spread. River rocks are like small boulders and should be not be dumped haphazardly; arrange them thoughtfully to resemble a natural water feature.
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