Can I use lava rocks as mulch for crape myrtles?
The purpose of mulch is to retain moisture, insulate the soil from extreme temperatures and reduce competition for soil nutrients by discouraging grass and weeds. Mulch also adds nutrients to the soil as it breaks down over time.
While lava rocks may be attractive in the landscape, they will not retain moisture and will actually increase the temperature of the soil during warm months. In addition, lava rocks are quite difficult to work around in the landscape and may cause unexpected problems.