I`ve use red lava rock that comes from "Lake County" in northern CA.for over 10 years.When I screen out the "dust", I notice that during the first few waterings I see slight red color coming from bottom of the pot.In past I have washed & screened some & it wasn`t worth the effort,so I just screen out the dust & use about 40+ % in my mix..This lava comes from Mt Konocti beds formed many years ago.--Z

I know this is an old thread but I wanted to update what I did over time to get "rid" of the lava rock problem that we had. This last week, I finally scraped alot of the remaining rock out of the large bed and spaded topsoil, compost and some organic fertilizer into the soil. However quite a bit of the lava rock remained and I spaded that in along with the amendments. I simply could not get all the rocks out with a flat type of coal shovel. I double dug the areas adding amendments each time along with organic fertilzer, soy pellets, etc. (Not alot of fertilizer but a sprinkling to get things cooking along with the compost in there.) Of course this was heavy, sweaty work but it is finally finished off. I wish I had been able to get almost all of the lava rock out of there but too much of it had already been mixed in with soil over the years and I simply couldn't get it all out without removing ALOT of the soil along with it. But I was able to spade the vast majority of it back into the amended soil before adding a final layer of topsoil, compost, soy pellets and wood mulch. (In the end I probably added back 4 inches of amendments to make up for the removed lava rock and put another 3 inches of wood mulch on top of all of that.) So now most of the remaining lava rock has finally been worked into the soil where it can hopefully decompose more quickly and become part of the soil. I NEVER recommend lava rock or landscape fabric to anyone but if you move into a house that has them you can probably get away with leaving some to dig into the soil. I say this because after all the amendments and digging in of the remaining lava rock (which was still a fair amount of lava rock) the final "soil" drains well. (But it took ALOT of work that wouldn't have been necessary if I had never had the lava rock in the first place.) The plantings are doing very well but I'll know more this summer when the wife plants flowers into this newly amended soil with some lava rock spaded in. Time will tell. In the end though, I WILL NEVER use lava rock or weed barrier fabric on my garden ever again. These were the two biggest mistakes I have ever made in all my years of gardening. Just my personal opinion. (The reason I got rid of mine and/or incorporated the remaining lava rock into the soil was it had become unsightly over time and some parts stayed too damp and a small bit of moss was growing on some of them. This situation had to be corrected because it was really bugging me. LOL!) Finally, I was surprised to find quite a few earthworms in this old "lava rock" soil when spading in all the new stuff. That did really surprise me, I didn't expect to see earthworms in this old stuff. Now the earthworms have a good soil to live in!! (I hope!!)

A long time ago I read about lava rock having a high fluoride content. I now found this info at simplyhydro.com: -- Lava rock has successfully been used used in hydroponics for many years...but less so now, due to other alternatives which do not have sharp edges that cause damage to the roots. Also due to chemically treated lava being hard to find in many areas of the country. -- (This makes me want to it use much less than I have before...) I have crunched up lava with a sledge hammer but found it tedious. It does make contrasting topping for bright succulents. Re: "no peat" mix. I read about peat being acid and consequently inhibiting fungus. I also read about most cacti and succ.s not being too particular about the ph of the soil. So I grew some smaller echeveria types and a couple of others in pure peat, with a wick in water, like African violets. Some are going on 4 years now. I've been amazed. Lost a couple - likely because that peat had some soil, too, which provided a fungus foothold. I followed up on "chicken (granite) grit" from another blog. Yup, the local farm supply had it. Cool stuff. The Rockies in a bag. Heavy, but a lot of people recommend it: 1 part grit, 1 puffy stuff, 1 fine peat.

Lisa thank you for explaining the short garden. I would not use any rock as a top layer and if I was forced to do so lava rock would be my last choice. River rock is better looking in my opinion. It looks like others have described why it is not a good idea so I will just say I agree with their reasons. There is even a new term in landscaping, it is called gravel regret. I don't know how your parents found their designer or how skilled he is. For all I know it may be your parents who suggested lava rock. If they are determined to have it, black would be my choice. Even if your parents were young and agile I would still like to see the tall shrubs removed. It is not a good look. To make things even easier they could remove the sheared shrubs. The house is so nice, it does not need dressing up and I think ground cover and a few other plants would be all that they need. If you find it is the designer who suggested lava rock then I think you should examine the whole design. You can not have faith in a designer who would make such a suggestion.