Is lava rock an acceptable substitute for tufa rock? One of my books suggests drilling holes for plants in lava rock if tufa is unavailable. Another book says lava rock melts too quickly in the rain and is unsuitable for planting. Has anyone tried doing this? Shall I be the guinea pig? I have piles of lava rock and I'm already using redwood containers for my alpines instead of tufa or hypertufa troughs.
Lava rock
I've used both tufa and lava, but both are very difficult to obtain in my area. My small chunk of tufa was imported from Calgary. The lava rock I use is pumice. I drilled a hole through it, placed it on the ground, filled the hole with proper soil then planted a Sempervivum in it. Three years later the pumice is hardly visible as the sempervicum has cascaded down the side (and rooted into) the pumice. So yea, pumice can work....I'm not sure about the rough, sharp type of lava rock like you see in BBQ's, although I see no resaon why not. My climate is far wetter than yours (over 60" of precipitation a year) and I see no deterioration in the pumice. If anything, both it and the tufa are being overtaken my moss.
Hey thanks, Todd, I never even thought of pumice. There's an unlimited supply of that here, very cheap by the pound, and I have already edged some of my flower beds with it whenever I've been too low on cash to buy more substantial rock. It's also a lot easier to handle. A veritable boulder of pumice is easy to move from place to place. My son and I used to carve little animals out of small pumice rocks. I'll try both, pumice and lava rock, and report back.