Lava rock in gritty mix

Joe1980(5)June 2, 2014

I'm interested to know where lava pebbles rank as an ingredient for a gritty mix variant. Right now I use turface and grit, in equal parts, but wonder if lava rock pebbles can be mixed in, mainly for athstetic reasons. I have liked the look of it since seeing Josh's (greenman) mixes. Also, lava pebbles are lighter in weight compared to both turface and grit, which would be great for bigger pots.

With that said, is it feasible to use lava rock, and what kind of moisture retention does it have compared to turface and grit?

Also, at what ratio would it work best in conjunction with turface and grit, to maintain similar moisture levels?


This post was edited by Joe1980 on Mon, Jun 2, 14 at 9:30

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drew51 SE MI Z5b/6a

I think lava rock holds about 50% of what turface does. Pores are much bigger. Grit holds zero, well surface tension holds some.

    Bookmark   June 3, 2014 at 7:58AM
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calistoga_al ca 15 usda 9

I would feel good using up to 50% lava rock as part of my granite fines. Al

    Bookmark   June 3, 2014 at 10:10AM
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greenman28 NorCal 7b/8a

Grit/Granite holds ~14% moisture on its surface.
Lava rock (scoria) holds less overall moisture than Turface, and the pores are quite large. I absolutely love working with it.


    Bookmark   June 3, 2014 at 11:28AM
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So basically, lava rock is right between grit and turface. That would lead me to believe that if used to replace any fraction of grit, it will add moisture, and if used to replace any fraction of turface, it would reduce moisture. So, if I were to use 1:1:1 of all three, it would pretty much hold the same moisture as my current 1:1 turface/grit combo.

Good news is, even up here in Wisconsin, I've found a source of red lava pebbles either in bulk or in 60# bags. The size they claim is 3/8" and under, which seems good to me. I will obviously sift out the fines like I do turface, but what size should I sift on the upper end?


    Bookmark   June 3, 2014 at 12:00PM
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greenman28 NorCal 7b/8a

What a great resource!
Sift at 3/8 inch, if you need to remove some large pieces. Rinse the lava rock many has so much of that red silt, it's amazing ;-)


    Bookmark   June 3, 2014 at 8:47PM
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It's amazing what you can find when you try. I've got great sources for turface, #2 cherry stone, which I believe is the finest looking grit you'll find with its purple color, and now lava rock. The killer around here is the pine bark fines, which I had, but the source dried up. I don't use it anymore anyway, so it's ok. Heck, I even discovered a source of not-so-common succulents this spring.

As for the rock, I'll have 120# of it, so I think I will be set for a while. I'm thinking whatever I sift out that's too big I will relieve a little stress and bust it up into smaller pieces. Unfortunately, this idea has come after all my repotting this year, so I won't have anything to pop into my new mix.....unless of course I buy more stuff. Either way, thanks for the input, as well as the nice pictures scattered around the forums that inspired me to seek out lava rock.


    Bookmark   June 3, 2014 at 9:39PM
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Where did you find Red Lava Pebbles? We live in Madison, and used to get them from Menards, but they no longer sell them.

    Bookmark   June 5, 2014 at 11:29AM
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Sounds like you have found some great resources in your area for soil building. Very nice indeed. I have never used cherrystone and cannot find it locally but I know some people on here use it and really like it in their containers.

Some people also use lava rock (scoria) in their mixes and report great success. Again, have not found a source of it in my area but I will keep my eyes open for it. They have some lava rock at places that sell grilling supplies but the pieces I've seen are much too large for container use.

The great thing with these mixes is that growers in different areas of the country, or the world, can substitute materials found locally and build with a soil that works well for their plants.

Thanks for the update.


    Bookmark   June 8, 2014 at 7:44AM
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