Brooke - sure it is. You're just using an external reservoir.
Idaho - lava rock works OK, but I have a few concerns about its use as a potting medium: it does hold a lot of water, but a large percentage is in that coarse surface porosity. Being in large droplets right at the surface, the water can easily bridge the open spaces to clog air flow to the roots, so you need to use quite a coarse size to keep more open space, but that leads to poor capillarity. Secondly, studies (not mine) have reported that the stuff traps minerals and plant pathogens really well, degrading the overall conditions slowly over time.
You also have to be careful about the specific lava rock used, as some are relatively neutral, while others are quite chemically active, containing readily-dissolvable minerals that can poison the plant. That's definitely the case with ash clinker - it's usually loaded with soda ash.
|