Can You Use Lava Rocks in a Planting Bed?

Heat Tolerance

• Lava rock creates a "heat sink" in beds and areas around them, according to the Colorado State University Extension. This creates microclimates with warmer temperatures from afternoon through nighttime, which in turn creates the need for increased irrigation. Warm temperatures and dry soil aren’t a problem for drought- and heat-tolerant plants, such as the type used in xeriscapes. Compatible species for lava rock beds include shrubs such as the century plant (Agava americana), a 6-foot-tall shrub that thrives in hot, dry sites. The Chihuahuan orchid shrub (Bauhinia lunarioides) also grows well in arid climates. This 8-foot-tall evergreen has gray-green foliage and blooms with pink and white flowers in spring and fall.

Sun Tolerance

• If your lava rock is light or white, it reflects sunlight onto plants, radiating heat and light. To compensate, choose plants that tolerate intense doses of direct and reflected sunlight. The triangle leaf bursage (Ambrosia deltoidea) thrives in sunny, dry sites. This fast-growing, 3-foot-tall evergreen shrub has a rounded form and silvery-gray foliage. It grows well in rock beds and thrives on natural rainfall. Desert marigolds (Baileya multiradiata) tolerate sunny, rocky sites and require little irrigation. These perennials grow to 1 foot tall but spread up to 2 feet wide and bloom with bright yellow flowers in spring and summer.

Alkalinity Tolerance

• Some lava rocks contain limestone, an alkaline substance that raises soil pH levels, reports Ohio State University. Most plants thrive at a neutral or slightly acidic pH level -- less than 7.0 -- but some species tolerate or even prefer soils with pH levels above 7.0. Appropriate species for lava rock beds include the saltbush (Atriplex canescens), a 5-foot-tall shrub that spreads to 4 feet wide. This drought-, heat- and sun-tolerant evergreen has gray-green foliage and blooms with yellow flowers through late summer. For fall color, plant an emerald carousel barberry (Berberis x “Tara”), a deciduous shrub that turns orange and red in early autumn. This 4-foot-tall shrub tolerates sunny, alkaline sites and produces long-lasting red fruits.

Ease of Maintenance

• Lava rock beds make cleanup of fallen twigs and foliage difficult and interfere with rejuvenation pruning. Avoid these issues by choosing low-maintenance evergreen plants. The cliffrose (Cowania mexicana), a native North American shrub, grows to 6 feet tall and thrives in sunny, dry sites. It has gnarled branches covered with light-green foliage and produces aromatic, white flowers. If your lava rock is dark or in a shaded site, plant kinnickinnick (Arctostaphylos uva-ursi), a low-growing evergreen that forms a mat of foliage, accented by pink flowers and red fruits.