Lava Rock. How Do I Use It?

cattleya17(6b/NY)November 2, 2007

Hello i got some lava rock and i need to repot my B.nodosa because its rotting. i posted about this before in 911 emergency. so i finally got the lava rock but it is now 6:33 P.M. so can i repot and do sone recostructive work on my plant this late? and to use the lava rock do i need to soak it before i use it and once i do repot with it do i regular water or do i soak my plant in a tub? Please any help would make me very happy!!!!!


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aachenelf z5 Mpls

It's easy. Wash the rock. Put some in the pot. Put the plant in the pot and pile some rock around the roots to make it secure. Don't be concerned about filling in spaces. That's the beauty of this stuff - lots of air movement around the root. Should take you about 2 minutes.

Don't soak when you water. Just pour water through the pot. The lava rock soaks up water very quickly and will continue to release it slowly over a few days. Don't be too quick to water again. This stuff is deceptive. The top pieces may appear dry, but down in the pot the rock will be slightly damp for a couple of days depending on pot size, temp, air movement etc. In your case, it's far better at this point to underwater rather than overwater. I think you'll love this stuff.


    Bookmark   November 2, 2007 at 7:04PM
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Make sure to rinse well, or you'll constantly have reddish (or black, depending) water draining out of your pots. The red dust also tends to stain. After potting it up, I'd suggest shaking it gently to see if the plant moves very much. If it flops out or threatens to, you might want to cram a little more rock in.

Kevin is right on about watering. It's great stuff.

Good luck!


    Bookmark   November 2, 2007 at 7:07PM
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I used 100% red lava rock for Australian dendrobiums and sarco's. (Black lava rock absorbs too much heat.) Here's what I do: Wash away dust/chips under running water. Soak in distilled water (* see note below, I'm sure regular tap water works as well) for 10-15 minutes, then drain and air for a little bit so most of the water on the rock surface evaporates. Then use as orchid media. Larger rocks for lower 1/3 of pot, and finer rocks for the upper 2/3 of pot. I do *not* water the freshly (moist) lava rock repotted orchid. Lava rock is porous and holds a large amount of water: test this out yourself but weighing a dry portion -> then soak in water, drain, shake off surface water -> then re-weigh.

* = I use mainly distilled water for my orchids. The downside of lava rock is that they tend to collect minerals/salts from hard water. With time, these show up as off-white precipitate along the tiny tips of the rocks. Flushing the media once every 1-2 months is a good idea.

Good luck, alvin

    Bookmark   November 2, 2007 at 7:21PM
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lwowk(6-B NJ)

I am also interested in Lava rock. I am planning of trying this with some of my Dends when time to repot. Do Phals, BLCs and Onc. grow well in this stuff too?


    Bookmark   November 2, 2007 at 10:08PM
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Firstly, if the media that you've been using for your orchids work, then why switch to lava? I'm new to lava myself. Only started using it this spring to counter over-watering tendencies. Still, it can hold a lot of water as folks here have noted. Do read previous posts on this forum about lava rock usage. The major downside with lava rock is that it absorbs/precipitates salts/minerals in hard water. If you're using rain/distilled water/naturally soft water, this should not be a problem.

My dendrobiums (all sorts) are in 100% red lava rock in clay pots - they seem to do very well. My phalaenopsis (amabilis, bellina, etc.) are in clay pots with larger (~3/4" diameter) lava at the lower 1/3 of the pot, and 1:3 finer lava:fir bark mix for the upper 2/3's - they seem to do great too - indoors, South windowsill. Cannot speak for oncidiums and BLCs - I imagine they'd do fine in lava since they like to dry between watering. Hope this helps, alvin

Here is a link that might be useful: Lava and Phalaenopsis

    Bookmark   November 2, 2007 at 11:40PM
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