Lava Rock

[Sharyn]

I received some dens from Hawaii in August. They're potted in lava rock and perlite. I've read that the lava rock does not decompose so just wondering if this media can be cleaned and reused when time comes to repot. The roots are all over the tops of the pots and flowers still blooming.

Perhaps they're all blooming now because they were grown in a much warmer climate. Looks like they may remain in bloom for awhile so I'm not sure when to expect any new growth, check the roots and repot, if necessary. At any rate, I'm curious how often the lava rock needs to be replaced or IF it needs to be replaced? Anyone using this media?

[Tobi]

Hi Sharyn,
Lava rock does not decay or break down, therefore it can be reused as a
potting medium provided it is sterilized. It is well aerated in the pot and retains
water pretty well although not a much as fir bark. There is no nutrients in
the rock so a 20-20-20 fertilizer should be used as a supplement. Another
advantage of its use is that it adds stability to the pot. One disadvantage is
it does tend to accumulate salts, so if your water contains dissolved minerals
in large amounts, there could be a buildup of salts. One of the local growers
uses it with his Paph mix with good success.

[Sharyn]

Thanks Tobi. I like the fact that the media is well aerated and doesn't hold too much moisture. It drains quickly and seems to be working for me. Can you suggest a way to sterilize the lava rock?

[Tobi]

I would soak them in a 10% bleach solution, followed by a thorough soaking
in distilled water overnight.

[Sharyn]

Great - will do when the time comes. Thanks for the help.

[Cynthia, Prescott, AZ]

I have seen Critter Creek on their Web site recommend against liquid sterilents for clay pots, and I think that recommendation would hold for lava rock. I think they recommend the oven at 400F for 3 hours.
Critter Creek Laboratory ("Thoughts on Viruses and...", bottom of page)

I have also heard that running an electric oven thru its 'self clean' cycle is hot enough and long enough to do a good job of sterilizing pots.

[Tobi]

You can sterilize them in an oven that way. I've even heard of some people
broiling them in their oven. Heck, you could probably even throw them in
some aluminium foil and put them on your grill for 10 minutes. I only recommended using the bleach in order to get rid of the mineral deposits
that may have accumulated on them over time which the other methods
would not do.

[articuno75]

What about boiling them in water? I wouldn't use tap due to the residue that might cling to them but maybe bottled water instead.

[Cynthia, Prescott, AZ]

I just finished a discussion of boiling pots for sterilization (plastic in my case that take boiling well) on the Orchid Guide Digest email forum. There are some very knowledgeable people there, much more professional than I. The consensus was that boiling is not good enough. Not good enough for orchid virus and not good enough for fusarium spores, my particular concern. Type of water will not make a difference.

[MSPProductions]

Sharyn, I've been trying out red lava and other stone mediums. I've been baking the stone like Cynthia noted. I've been told that my plants wont bloom because I also use tap water and that it's a bad combo...but I'm doing it anyway and everything seems fine so far. We'll see

[Sharyn]

Cynthia: Thanks for the link - very helpful. Looks like baking will be the easiest and safest.

MSP: I use rain water when I can, otherwise the tap and give the plants a good flush occassionally to get rid of any mineral deposits. Hope this will work for me too as I've only had these plants for several months. I guess I'll have to wait and see.

Thanks for tips everyone!

[PhalPal]

Sharyn I have a mini-catt in Dynarock, similiar to Lava Rock, perhaps not as porous. It is doing great in this stuff and I don't feel I need to worry about over-watering. I was told by the vendor to use 10% bleach solution and soak overnight if I wanted to re-use.

The problem I see with this is rinsing, and rinsing, and rinsing....

[sandra]

Sharyn, I have all my Catts. in Dyna-Rok (like Connie) and some in Hydroton. Although I may never see blooms because lack of light issues, I love this growing medium, lightweight and roots take to both, beautifully. These 2 mediums can be used over and over. I always soak over night before using with a little anti-bacterial dish soap and a capful of Physan 20. If the lava rock is the same as Dyna-Rok, you can recycle!

[slippery_biscuit]

One more cleaning option... if you have the appropriate basket you could put them in your dishwasher and run them thru the sanitization cycle. As this procedure satisfies DSHS here in WA with regard to cleaning dishes, I have to think it might also work with our plants.

cheers!

[wieb]

I am no expert on potting media for orchids. I have maintained aquariums for a couple of decades. And I know a bit about chemistry through college and my job.

Removal of chlorine from water is essential in the aquarium hobby. Aquariums stores have "water conditioners" that contain sodium thiosulfate which rapidly neutralizes chlorine or residual bleach. It is harmless to fish in small quantities (you add it during water exchanges).

If you are going to sterilize with bleach, be careful and neutralize it well. Bleach is used to sterilize aquariums and it is really hard to get the odor out (it seeps in every imaginable pore available), even after rinsing many times. The odor means the bleach is still in the system. I imagine the lava rock must have millions/billions of pores for this bleach to seep into and hide. I would guess that you could rinse it for 20 minutes straight and you could still smell the bleach. I would rinse it well (several minutes of continuous running) and then I would soak it in a dilute mixture of this water conditioner for about 30 minutes with occasional stirring. The water conditioner is typically used at about 1 ml/gallon when neutralizing tap water -- I would bump it up to 5 ml/gallon for neutralizing residual bleach. Then pour off the neutralizing solution into the sink and flush again for a couple of minutes with fresh water. The bleach odor should be gone. If not, repeat the treatment with a higher concentration (maybe double). The sodium thiosulfate is free rinsing and any trace amounts would not hurt orchids, I am sure, since it doesn't harm fish.

By the way, bleach does not dissolve most hard water deposits and salts. White vinegar (acetic acid) is good for this. A 50%/50% mixture of white vinegar with water is good at solubilizing hard water deposits and is also used throughout the aquarium hobby. But then you would have to worry about attacking the lava rock; rinsing from the pores; resultant pH of the medium. Probably the best advice is what I see all over the forums – don’t use lava rock if you have really hard water because it will collect the hard water salts on it.

Here are two links, one talking about bleach neutralization and the other about removing hard water deposits, in case you are adventurous.

http://www.newton.dep.anl.gov/askasci/chem00/chem00046.htm

http://www.howtogetridofstuff.com/stain-removal/how-to-get-rid-of-hard-water-stains

[wieb]

I just realized ... many of you more experienced orchidists (is that right?) may have used bleach many times to clean lava rock with no problems, and without any neutralization step. So the trace amounts of chlorine left may not be of a high enough concentration to cause problems ... but I am sure you can not rinse the odor off of it with just water. (The trace odor would be deadly to fish.) I would think the neutralization step would be a cheap, easy insurance step to protect our prized orchids. A bottle of the water conditioner (~$7 for 6 oz. bottle) would last a long time and would be enough for many treatments. It is what I would do ... but I am just a rookie. Good luck.

[pikevi]

wieb: I think you are right about chlorine. Bleach is rarely used in aquariums now. The exception is when 'ICH' (Ichthyophthirius sp.) lingers on.

Even the acid loving cichlids (discus) will die if a minute amount of chlorine is present in the water. It is not the acidity that kills the fish but the chlorine will affect the circulatory system causing the heart to fail.

I used lava rock ( quite expensive here) in aquariums but cleaning it is a big headache. Direct sunlight helps a lot . But short of boiling them under pressure (autoclaving) they cannot be cleaned effectively.

But as you said orchidologists will have the practical knowledge and/or experience to recommend their use with orchid medium.

To be frank I have never heard of lava rocks being used in plants before. I don't know if the high amounts of Iron (Fe++) found in them may be useful to plants.

[Nancy]

What type of store carries Dyna-Rok? Can it be found in a pet store, like Petco?

[Orchidflowerchild]

Well, as for repotting, are you expecting to remove the lava rock from the roots of your plants? THat's just not likely to happen, and if you did, you'd likely have no roots left. The benefit of lava rock is that you can just pot up by setting the old pot in a new pot and filling the gap with more lava rock. No complicated sterilization needed.

-Cj

[Hummer344]

Nancy,
Dyna-Roc is not available in many stores but can be bought on line @ Dyna-Gro. I have used it in my orchid mixes for years and am currently doing a home experiment using two Phals.(the same variety) One in pure Dyna-Roc(a mix of medium and fine roc) and one in my usual mix. Both plants are healthy & neither are blooming. The only difference I see is that the dyna-roc has settled a lot more & I had to fill it up after a few months.