Three types of lava rock are used in landscaping: red-hot, black and sunset. Red-hot is the color of red brick. Black lava rock ranges from gray to black, and sunset is a combination of red-hot and black. Lava rock does not fade, conserves moisture in the soil, doesn't wash away, helps control weeds and serves as a natural insulation for plant roots. It is simple to use it in your landscaping.
Rake leaves and other plant debris from around the base of your existing plants. If you are creating a new garden, outline the area for the bed with a hose, string or lawn-marking paint. Remove the sod in the outlined bed.
Install the edging, if you choose to use it. Edging helps keep the lava rocks inside the flower bed, so that they are not hit with a lawn mower, and it helps keep weeds out of the flower bed.
Spray water over the entire bed, applying at least an inch, as the water helps pack the soil. For additional weed control, install weed barrier material before you layer the lava rock. While lava rock generally prevents weeds, a few may grow through.
Lay the lava rock in a layer around the base of the plants and throughout the flower bed. Lava rock is best used in beds that feature shrubs and other tall plants, because of its thickness. Do not allow the lava rock to rub the trunks and stems of the plants, as it could cut the plant, but get it as close as possible. Since the lava rock is thick, one layer is all you'll need.