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!!)

Sounds like a great idea

I live in a "Manufactured Home Community - moble home park." My home is copletely surounded by LARGE - about 6" circumference, hazardous to someone my age. It's been neglected for who knows... long enought to have weeds so thick I can't keep up. It is SO ugly! I can't afford yard people but maintenance is Park Rules. I am disabled & am at a loss to get any answers, for I do have some DIY low cost ideas. Can I do a Layered No Dig Scape over the top of the lava rock? I don't know. I do know I can't dig it out & I wouldn't!

Thanks @tapla (mid-Michigan, USDA z5b-6a), your answer was extremely helpful, and exactly the kind of help I was looking for! I'm very grateful for that! There are few things I want to say, as I didn't specify exact soil mix I planned to use and details about it... You asked me why would I ruin my perfect soil particle mix by using small organics like coir... Well I did not know that much about particle size importance when I was buying stuff for it, also lot of people made very simillar mixes (I based my mix on youtuber "Cactimania" one that used 1/4 organics like loam compost or coco coir with worm droppings and 3/4 lava pumice and grit, since he lives in UK and I in Poland and our weather is slightly more dry so I wanted to maybe make it slightly less fast drying so it would hold water a bit longer - hence the 1/3 organic...) I also heard a lot of good stuff about coco coir an how much plants love it, I've heard it also holds air pretty good and most importantly isnt that annoying to water as peat, as I absolutely hate how it shrinks, becomes hydrophobic and sticks to roots like it had some glue in it about the dust on lava I was just really curious especially that many sources stated it has a lot of those minerals but after your recomendations and the ph I discovered it had I defintely gonna wash this stuff off I was planning to make a mix 1/3 organic or 1/4 organic and it follows something like that: 1 Part Coco Coir + 0.5 part Worm Droppings 1 Part Red Lava Rock (I ll try to do something about the size) 1 Part (or 1,5 Part) Pumice (1-5mm) 0.5 Part that weird grey lava rock (1-5mm) About the Coco Coir: I bought Plagron Coco brix which are supposed to be buffered with calcium, as well have adjusted ph, trichodermia added, in general they are supposed to be highly processed and I've read good reviews about it... I wanted to use it since I've heard that it retains water in a good way but also its quite loose so it still holds air and it is less annoying than peat to water About the worm dropings: I dont know what to say exactly, they were supposed to be "soil conditioner" and "add organics" into the mix They are also from Plagron since I was buying from one hydroponics shop, they look to have a lot o peat in them and dont disolve a lot of stuff in water, since it only looks murky from the dust but doesn't change color that much... On the website it doesn't provide much info either and says that they dont provide much nutriens as a fertiliser... Next time If I will be using them I will buy local ones, that appear to be better quality and dont have much peat and rather actual droppings high in organics made from horse manure processed by worms... In general I planned to use them more as weak organic fertiliser for the coir so it isn't totally empty... Also I decided to measure ph of the lava and rest of the stuff and oh boy, I'm making sure to wash all this dust off! While the ph of gray lava dust appeared to be slighly basic but close to 7 (maybe 7.5?) the ph of red lava dust was definitely above 8, probably solid 9 since it was all nice blue on the indicator the ph of Coco coir was something between 5-6 and worm dropings were something arround 6,5 maybe 7? - they were hard to measure the organic stuff had ph as advertised while the lava was supposed to be neutral - DEFINITELY wasn't (ofc I used good quality deionised water, but had only liquid ph indicator and those ph strips that are just a pain and a mess, I kinda need to buy digital ph meter) here are the results if you are curious and wanna see the mess I made trying to measure ph of these things: https://imgur.com/a/pD88EDc So what I'm gonna do now? Im not sure exactly... I've read your responce as well as link included and there was A LOT of info to take in, so I kinda need to read it few times again You recommend me using other things than coir, like fine pine/fir bark that I would need to buy (but also find in right size, which can be sometimes a pain like with that lava rocks)... Im definitelly still gonna use that lava and pumice but defintelly gonna wash it I was trying to create really good mix, maybe not the perfect one, also I wanted something that actually will hold good amount of water (but not in a soaking wet way but rather lightly moist but for longer) and still provide air between the water holding medium... Im not that concerned about the medium decomposition as I plan to repot them more oftem like every other year my cacti even in store bought soil they had when bought grow really fast (altrough they are in very small pots and when I water them I touch the soil with paper towel to drain the excess - since its completly detached from the pot and in one piece) that is the reason why I really need to repot them as I did not expect them to outgrow the original pots and soil that fast... Soooooo as I understand I could use Coir + wick combination to drain excess water and maybe even use it to water plants through it (I actually thought about this so maybe I could water my plants with less effort) Or pine bark instead and water normally I kinda do not know what to do since I totally wasn't concerned about coir and rather just on lava, now Im like back to the hanging point but instead of thinking of lava I think of coir... My only concern is that the pine bark chips will dry too fast tho Again I have to read your link once more and think about this, also Its quite late and I need to go to sleep... Thanks again for the answer and info!