Using lava rock to pot all my orchids.

[Mrmilbourn1980]

So I have discovered lava rocks and I absolutely love them so far only about 5 weeks in to using them I bought two little itty bitty vandals from Lowe's last year I got absolutely nothing out of them until I planted them in lava rock about 4-5 weeks ago now I have new growth new roots they are doing 100 percent better the 2 dendrobiums that I own that were rescue orchids from Lowe's are responding very well new root growth and I think the dormant pseudobulbs are starting to grow. One of my three cattleyas are in lava rock they seem to be doing very well. The other two are still in the original substrate I bought them in. All my phals except except 2 are rescues from Lowe's and Wal-Mart the ones that are in lava are doing great. I grow under a 250 watt Mars hydro led light I dimmed it down to 150 watts low humidity in my bedroom so I spray every morning and water pretty much every day I don't think I can over water them this way tons of new growth most of them have a lot of pigmentation from the led light. When I buy a orchid rescue and stick them under this light they seem to bloom a few more flowers it's pretty interesting . even if I repot them anyone have bad exp with lava rocks

[SouthPark]

Mrmil ...... welcome to the forum! I see it is your first post.

I grow most of my orchids in scoria (lava rock) too. For tropical regions, generally really good results (I have experienced).

I do know that if the humidity becomes relatively low, then lava rock can certainly dry out relatively quickly. But watching the orchids like a hawk and making watering adjustments appropriately until humidity gets back to usual high levels (of tropics) overcomes issues associated with low humidity.

In general, it is 'harder' to over-water with scoria/lava-rock, but not impossible to over-water. I think the important thing is to just have some rough idea about the state of the media and the roots ----- and avoid roots running low on oxygen intake. And one possible undesirable situation is roots becoming too watery for relatively long periods of time (and water not moving much in and around the roots). If that extended watery condition is avoided, then that will be nice (for the orchid)!

I have friends and know of lots of people growing in bark or bark/perlite mix ....... very successfully. Whatever is used is fine ----- as long as everything is kept under control.

A few reasons I use scoria/lava rock in my region is that --- it works nicely for me, and it's relatively inexpensive, and it's inorganic ------ it pretty much doesn't break down. Also very readily available where I live.

Originally Posted by Mrmilbourn1980

itty bitty vandals

vandals are nasty!!!!!

[JScott]

I just purchased a big bag of scoria, based upon what I've read here, primarily from you, SouthPark. I'm intrigued by it, and I've got a few Catts that need repotting, and I'm going to try them in scoria. 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?

[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!

[My Green Pets]

I had several of my plants in lava rock and plastic pots. They did really well for the first couple of years and then the roots did not look so good anymore. I have been told that red lava rock absorbs salts and eventually becomes toxic to roots.
This year I am trying out some things potted in granite! Roots seem to like it so far, hopefully they will stay happy.

[DirtyCoconuts]

i think that excluding my mounted orchids and the ones i am doing in SH with LECA all but the Phals are in some amount of lava rock.

I use it mixed with perlite and charcoal as my go too mix and i add some good bark if the plant needs more moisture like my dens and oncys.

NO bulbos ( right on leafmite!) but i cant think of any other species i don't use it with.


i flush all my plants pretty much 3 times a week so i don't know from rocks going bad