Using lava rock to pot all my orchids.

[SouthPark]

Originally Posted by JScott

I ordered the medium scoria, because I use medium bark for my Catts. Does that sound right, or do I need a different size to account for the different properties of the medium?

JS ----- medium size scoria, maybe 10 mm to 15 mm average diameter (since some companies are less strict with their sorting, so there can be more differences in average size ..... but that's usually ok) ----- has worked well for me with mature sized catts.

I even have a big mature sized paph ----- Paph. Saint Swithin 'Jill' that has been growing excellently in that medium size scoria.

I also have a bag of smaller size scoria ----- 5 mm to 8 mm average diameter, which I use for small juvenile orchids. I grow my Phrag. Grouville in this smaller size scoria, and Phrag. Elizabeth Castle too. Both doing very well. They've been growing long enough in it for me to know that they'll continue to grow in that without issue for the long haul.

A couple of Paph. Wossner Black Wings - juvenile, but nowhere near baby size - also been growing well for quite a while in small sized scoria too.

I haven't used red scoria before, but have been thinking about trying it out.

The colour I use is grey-coloured. They locally call it 'quincan gravel' ..... pronounced kwing-kun gravel.

I have Angraecum eburneum and Dendrobium discolor, both potted 30+ years ago in scoria .... medium size. And their pot has not changed. The scoria has not changed. They just grow outdoors, in full sun, never have been manually fertilised, and watered only by garden pop-up lawn sprinklers each night. The water from the pop-up lawn sprinkler is for the lawn, but also covers these orchids and surrounding plants.

For my other orchids in scoria ----- I fertilise just once a month with a weed pump sprayer, with weak fertiliser spray. Sprayed into the media ---- lava rock that is. Then a couple of weeks later ---- a similar procedure is carried out - not with fertiliser - but with weak cal-mag instead.

Also, don't be afraid to try approaches like layering, such as big pieces along the bottom and middle of pot, and small pieces up top etc. Flexibility.

And watering the media in a chosen band around the rim of the pot (or focusing more water in the outer region) can help avoid getting the bulk of the root ball too wet (under the orchid). And even if the roots do grow out to edges of the pot, the roots will meet the more wet regions on their own terms, and maybe get used to it - or adapted to it.

Originally Posted by CambriaWhat

I have been told that red lava rock absorbs salts and eventually becomes toxic to roots.

I've never repotted my orchids before (for reasons of media issue that is), nor have I ever needed to flush out the scoria with water. But I think that for those that fertilise more, or they know there's a buildup of fertiliser salts, then a flush-out every once in a while could be beneficial for the orchid(s).

I know of very good orchid growers that grow some orchids in pebbles and rocks even. As long as they know what to do with their media (eg. when to water and how much to water and don't mind to follow a workable routine), then good results can definitely come.

[Leafmite]

I believe that the main reasons most people fail with lava rock is:
1 Failure to flush the rock very well to get rid of unused fertilizer and fertilizer residue. This is so important since one is not changing out the medium every year as they are with bark or moss.
2 Not watering correctly.
3 Forgetting that the rock doesn't contribute significantly nutritionally to the plant.
4 Using too strong of a fertilizer when the orchid is kept too dry
5 Thinking that all orchids need the same care. It can be impractical to grow some orchids in lava rock. i.e. for me, these are: Phaius, Vanilla, tiny miniatures that prefer being mounted, Bulbos and the Pleuro that need constant moisture

[SouthPark]

Originally Posted by Leafmite

5 Thinking that all orchids need the same care. It can be impractical to grow some orchids in lava rock. i.e. for me, these are: Phaius, Vanilla, tiny miniatures that prefer being mounted, Bulbos and the Pleuro that need constant moisture

This is absolutely true (as with all those other great points you made) LM.

For vanilla, it can indeed be impractical in certain regions, or even various regions. In some places, like in my region, the humidity is generally pretty good and high enough to sustain the vanilla orchids. So my vanilla orchids grow just fine in scoria ----- which do get some water from the scoria, but also grabs a lot of water from the air through their tendril-like roots.

I'm thinking that in dry places, the vanilla orchid can get long, and possibly not enough water can get into it ----- so other media and methods of getting enough water into the vanilla orchid will be needed.

[JScott]

Originally Posted by SouthPark

JS ----- medium size scoria, maybe 10 mm to 15 mm average diameter (since some companies are less strict with their sorting, so there can be more differences in average size ..... but that's usually ok) ----- has worked well for me with mature sized catts.

I even have a big mature sized paph ----- Paph. Saint Swithin 'Jill' that has been growing excellently in that medium size scoria.

I also have a bag of smaller size scoria ----- 5 mm to 8 mm average diameter, which I use for small juvenile orchids. I grow my Phrag. Grouville in this smaller size scoria, and Phrag. Elizabeth Castle too. Both doing very well. They've been growing long enough in it for me to know that they'll continue to grow in that without issue for the long haul.

A couple of Paph. Wossner Black Wings - juvenile, but nowhere near baby size - also been growing well for quite a while in small sized scoria too.

I haven't used red scoria before, but have been thinking about trying it out.

The colour I use is grey-coloured. They locally call it 'quincan gravel' ..... pronounced kwing-kun gravel.

I have Angraecum eburneum and Dendrobium discolor, both potted 30+ years ago in scoria .... medium size. And their pot has not changed. The scoria has not changed. They just grow outdoors, in full sun, never have been manually fertilised, and watered only by garden pop-up lawn sprinklers each night. The water from the pop-up lawn sprinkler is for the lawn, but also covers these orchids and surrounding plants.

For my other orchids in scoria ----- I fertilise just once a month with a weed pump sprayer, with weak fertiliser spray. Sprayed into the media ---- lava rock that is. Then a couple of weeks later ---- a similar procedure is carried out - not with fertiliser - but with weak cal-mag instead.

Also, don't be afraid to try approaches like layering, such as big pieces along the bottom and middle of pot, and small pieces up top etc. Flexibility.

And watering the media in a chosen band around the rim of the pot (or focusing more water in the outer region) can help avoid getting the bulk of the root ball too wet (under the orchid). And even if the roots do grow out to edges of the pot, the roots will meet the more wet regions on their own terms, and maybe get used to it - or adapted to it.



I've never repotted my orchids before (for reasons of media issue that is), nor have I ever needed to flush out the scoria with water. But I think that for those that fertilise more, or they know there's a buildup of fertiliser salts, then a flush-out every once in a while could be beneficial for the orchid(s).

I know of very good orchid growers that grow some orchids in pebbles and rocks even. As long as they know what to do with their media (eg. when to water and how much to water and don't mind to follow a workable routine), then good results can definitely come.

The red scoria was used on my plants simply because that's what was available. Do you think it will make that much of a difference whether you use the red or black? I'll keep you updated on how mine are doing in the red scoria.

[SouthPark]

Originally Posted by JScott

The red scoria was used on my plants simply because that's what was available. Do you think it will make that much of a difference whether you use the red or black? I'll keep you updated on how mine are doing in the red scoria.

JS ----- I'm going to be trying red scoria myself, as they sell it in bulk at local 'home depot' equivalent hardware and plants store ....... in Australia, we have a chain called Bunnings.

I'm expecting no difference in performance between red and the grey scoria. I'll try it out anyway. I think red scoria is actually used a lot for growing orchids anyway.

I've got to pay a visit to the store to get other orchid accessories soon, so will grab a bag of red scoria! All the best JS!