Fans of Lava Rock

[SADE2020]

Hi

Anyone arourd that likes or have good experience with Lava Rock in exterior?

If, yes. Could you share some tips, please ?

Thank you!!

Sarah

[Leafmite]

I have used lava rock for my orchids since the 1990's with a little experimentation here and there...I now have all my potted orchids in lava rock. I just discovered the lava rock used for bonsai mixes and I am using that for the orchids that need more moisture (Paph delenatii and the Zygo's). The Cattleyas get the larger stuff. I do have miniature orchids that are mounted and some other orchids that are also in lava rock.

I have used basket pots in the past but currently I am using clear plastic pots with holes so the smaller rock does not fall out of the pot.

Lava rock works well for me because our summers are unpredictable and I do not need to worry that a cool, rainy summer will cause the roots to rot. Hot dry weather just means I need to water more often.

Lava rock is great because you can use a larger pot and give the orchid several years in the pot. The roots cling onto the rock quite well and when potting in a larger pot, you can just set the smaller pot inside a larger pot and add more medium. The medium never compacts so no need to change it.

The smaller lava rock seems to wick amazingly well and will stay damp for a couple of days after watering in cooler temperatures. I am guessing that it will dry quickly, like any other medium, when temperatures are hot/dry.

Lava rock does need to be flushed very well now and then to get rid of any unused fertilizer and one must remember that it is pretty neutral as far as nutrients go so one might need to add extra calcium.

The only con, I think, is that it is dusty at first and one should never rinse a large amount in a sink--use a bucket and dump the water outside in the grass. It can clog a sink.

[ArronOB]

Just clarifying what you mean by lava rock.
This stuff: Natural Black Volcanic Lava Rock Stone Aquarium Aquascape Fish Tank Random 1kg | eBay. Right?

Just clarifying as vernacular terms for rock can vary around the world.

Anyway, I’m interested in this question too. I’m getting tired of rotting bark and disturbing plants by repotting too.

Cheers

[estación seca]

In exterior... outside in the garden?

[Leafmite]

I use the red lava rock, the type used in landscaping, grilling and bonsai culture.

When I first started growing orchids, orchid bark was not easily available where I live and the stuff I did find would be great in early summer but by autumn, would be terribly compacted. Those early orchids would all be rootless by the following March. I looked around for something else I might use and landed on the idea of using some type of rock...the red lava rock was easy to find and very cheap. Bingo.

I like being able to put an orchid in a medium and then leaving it in that medium and not having to pot it in new medium every year. The specific sizes of lava rock are more expensive than the landscaping/grilling stuff I usually use but it is cheaper than the NZ moss so....

[SADE2020]

Leafmite! Thank you so much. This is such generous detailed information and is aligned with my test. I have already a lot of orchids in red volcanic 0.5 Phap to 2.0 Cattleyas.
However, I had a very bad experience in the winter due to too much cold and an unexpected wrong setup.
The lava rock also requires more nutrients than natural medium since don't hold much of it.

Thanks again.

---------- Post added at 08:27 PM ---------- Previous post was at 08:26 PM ----------

Originally Posted by estación seca

In exterior... outside in the garden?

Yes, Estación
Garden, but not without roof protection.

[SADE2020]

ArronOB

We are referring to Red Volcanic Rocks. The blacks are not recommend.
Hawaiian and Costa Rica growers used this type of medium. It is easy to find and as you can see it has Pros & Cons.

In my case I don't find good bark around here and SH has been good but not great for me to grow outdoor.

Hope this helps!

[estación seca]

Can you go into the countryside and collect your local cinders?

[Leafmite]

I always use pots that have holes so that there is good airflow. Sometimes, our summers are cool and very wet and my home is cool during the winter so access to air is important even with the lava rock for me.

[ArronOB]

Sade, I’ve always wanted to try lava rock (‘scoria’ here) but what puts me off is the persistent assertion that it will retain “salts” or “toxins” from fertilizer which need to be flushed periodically. I don’t like the randomness of that approach because as far as I can work out there is no way of establishing when the media is full of retained salts, how much flushing in necessary, or when flushing is successful and the media is again pure and non-toxic. So it’s all based on guesswork. Just flush periodically and hope for the best.

If you wait till it’s clear from the plants declining vigour that you have reached the point of media toxicity then, sorry, it’s already far too late.

Otherwise it would be the ideal media for me. I wouldn’t have any problem providing the moisture necessary as its fairly humid here plus I can water any time I want by simply turning the tap on. Providing the necessary fertilizer is no problem too, as orchids require so little and generally very much less then we give them. I also like the weight, much greater then bark, which prevents the pots from tipping over which is a constant problem in my growing environment. Further, removing the need to repot at the point of bark breakdown (approx therefore every 18 months here) would allow me to offer the orchids uninterrupted growth.

Finally, I note that most of the few species of local orchid that make it into general cultivation, although usually described as epiphytes, are in fact lithophytes. I include D. Kingianum, D speciosum and the Sarchocilus species in that. Presumably they grow on rocks because there is something about a biology of rock faces that they prefer - perhaps the species of microrrhizal fungus present, I don’t know.

I don’t know enough about the neotropical orchids that I personally prefer to grow to know how many are really lithophytes but I suspect it’s quite a few. There may be a very good reason why they would be happier in rock then in bark.