The power of scoria (lava rock)

[terryros]

I have been a believer in rocks with good drainage and fairly frequent watering with low concentrations of nutrients for several years. I have successfully been using Growstones to accomplish this, but the company folded and I know I will eventually run out of stones. I know you are in OZ, but what size of lava rock are using for your various orchids and anything else special about the material?

[SouthPark]

Hi terry!

Thanks for mentioning Growstones. I just took a look online to see what they are. They look pretty good!

I use scoria from local garden supply stores that either come in really big pre-packed chicken-feed bags for convenience ---- and these bags have categories such as average diameter 10mm, 15 mm and 20 mm.

Other supply stores have piles of scoria for our own gathering - so we can bring our own bags, or car trailers etc to fill up ourselves - as much as we like. The price here in Australia could be roughly 1 dollar per 5 kg, which is really good.

For regular size catts ---- juvenile to full size, I just use an average diameter of 15 mm. But the piles of scoria rocks actually have diameter that can fall within say 10 mm up to 20 mm. So I found it's no problem to have rocks that just range between 10 to 20 mm in diameter.

For example - at this website here that I just found a moment ago ----- they sell '20 mm' scoria ...... which is actually just fine. The photograph of the scoria clearly shows a big variation in the actual sizes of the pieces ---- which is no problem at all.

If for some reason my orchid pots fall over due to strong wind or something ----- scoria (and even those grow-stones you mentioned) won't roll all over the place.

I was actually initially thinking of trying out a mix of round leca balls and regular fresh-water river pebbles. But figured that it might not be a great thing if the pots fell over for some reason, and the leca balls would be rolling around everywhere on the floor. Big clean-up operation and 'tears' hehehe.

There are also other media that can be used here -- such as freshwater river pebbles (which probably requires more watering), and also those other sorts of rock called 'bue metal' etc. That's just their names. I hear some orchid growers will use that sort of rock for their orchids.

Terry - with the scoria ------ I think they were and still are popular just due to the way that they can hold in some water, but still allow the pot to stay relatively airy within.

Although - it definitely is still possible to make the scoria too wet for long periods of time (where regular roots can drown) ----- so compensation can be applied ---- by adjusting the watering method, or by using shallower pots and good drainage pots.