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Types of Landscaping Filler Rocks

By Casandra Maier ; Updated September 21, 2017
Decomposed granite is an environmentally friendly choice for a pathway or driveway.

Landscaping filler rocks are used for both function and aesthetic purposes. Filler rock is implemented in many ways in landscape design. It can be used at the foundation of buildings to create a rock bed between the structure and the turf. Filler rocks are also used to create an ornamental facade in areas where plants have a hard time growing. There are many different types of landscaping filler rocks, including pea gravel, river rock, rainbow rock, volcanic rock and decomposed granite.

Pea Gravel

Pea gravel is also referred to as Pete gravel and river pebbles. These small rocks are worn down and smoothed by wind and water over time to create an attractive finish. Pea gravel is available in many colors and typically used as a decorative ground covering. You can use pea gravel to create a boarder along dry riverbeds. It is also light enough to use as a mulch base around plants. However, pea gravel is heavy enough that it will not wash away with rainwater.

River Rock

Rive rock is almost identical to pea gravel, only larger in size. These filler rocks get their smooth polished finish from current waters in riverbeds. River rock has many uses for landscaping. It is used as ornamental filler in areas around plants and shrubs; it is also useful as filler in areas where grass would not be convenient. Landscapers use river rock to fill in strips of area between fences and pathways and also to direct water for drainage.

Rainbow Rock

Rainbow rock is slightly larger than pea gravel. This filler rock is made up of many different kinds of landscaping rocks, accounting for the variation in color and garnering the name. It is used to form aesthetic boarders and to create ground covering. In places where weeds are problematic, rainbow rock is used to hold weeds back and prevent them from growing.

Volcanic Rock

Large lava rocks are mined from the lava domes of volcanoes and later broken down into smaller, more manageable sizes. Volcanic rock can be reddish brown or black. Crushed volcanic rock is popular for use in dry climates as filler for yards and walkways.It is also used to fill in areas around paving stones. It has the lightest weight of all landscaping filler rocks and is cost-effective and versatile. It can be placed under the soil of a plant bed to help with drainage issues. Tiny holes in the rocks allow water to drain through, preventing soil loss.

Decomposed Granite

Decomposed granite is a filler rock made from chips of granite that have decomposed. It is reddish brown in color and available in a variety of sizes. Loose decomposed granite is an alternative to concrete and an environmentally friendly choice. It can be used to fill in driveways and pathways.