Another alternative is cinder. It's still lava rock, but in smaller particles.
Something I've noticed over time is that even small rocks eventually disappear when you regularly add oganic material on top of the beds. Yesterday, I planted my last rose for the season in a spot where it was impossible to dig because of dense rock when I first started this garden. (The rose first planted in that site didn't make it through my first winter up here.) I've just been mulching that part of the bed until I found a rose I wanted to site in that bed .. a few years
When I dug the hole, I could use a shovel an there were hardly any rocks to make digging difficult.
I've been mixing cinder with my back fill for a while and I find it works very well in this garden.
Smiles,
Lyn
