Hi all - I've been looking into ways to keep soil moist in a container but also allow drainage. I came across The Sill's lava rocks which mentioned it retained moisture (but specifically for planters that don't have drainage). I plan on planting outdoors in containers that do have drainage. So my question is, has anyone tried to use lava rocks at the bottom of their containers that have drainage holes to absorb and release moisture? or once there is a drainage hole are lava rocks pretty much useless? The plants I'm looking to grow will need to be well drained but with moist soil. At the moment I have time to water every day but when I go back into an office, I'm looking for an option where I can trust my plants will be ok every 3 days or so.