perlite vs lava rock

[Vanda lover]

I have used it unsterlized. It didn't hurt the plants in any way but there was moss and ferns growing after a while. Wash it well.

[dounoharm]

I used to use it right out of the bag after washing the dust off it...got it at lowes....use the bigger chunks for the vandas and smaller chuncks for other orchids...good luck!

[Cym Ladye]

One word of warning on lava rock: If you do not have a pure water source, some forms can absorb enough salts in one to two years to reach the saturation point where orchid roots cannot exist in the medium. Perlite does not do this.

CL

[Vanda lover]

That is true Cym ladye. I plan to change the lava rock once a year, and it is important to feed less and flush regularly. Our water here is really good, with very little mineral build up. I used R O water when we lived in Ontario, because the minerals in the water where we lived were very heavy. they coated everything. Things that I could never get minerals off [like our dog's water dish] in Ontario have cleaned themselves since our water here is so much better.

[weederwoman]

Do you think the lava rock and the expanded clay pellets are about the same for mineral build up, or is one worse than the other.

[Vanda lover]

Although I have heard that the lava rock is worse than pellets for buildup, I have seen no evidence of this so far. I started using the lava rock because we don't have anywhere here where I can buy pellets and lava rock is a fraction of the cost anyway. Lee valley tools sells tiny bags of pellets for around $30. It looks like about enough to pot one medium size plant. The ones you buy at hydroponic stores are much cheaper of coarse.

[ALToronto]

You don't actually need to replace the lava rock. If you can separate plant roots from the rock (and in many cases you won't be able to), you can place them in a mild acid solution (humidifier descaler will work well - it's pretty much dilute phosphoric acid) for a day, then rinse very well and use it in the same pot for the same plant.

If you cannot separate the roots, place pot, plant and all in a very mild phosphoric acid solution (pH of no less than 5) for an hour, then in pure (distilled or RO) water for a day. This should get rid of most buildup.

If you keep your fertilizer to a minimum (no more than 35 ppm N) and water with pure water at least once a month, you shouldn't get a buildup at all.

[Vanda lover]

I have often wondered if I could use a little vinegar in the water to bring acidity down and reduce buildup.

[ALToronto]

Originally Posted by Vanda lover

I have often wondered if I could use a little vinegar in the water to bring acidity down and reduce buildup.

Citric acid is better, but you MUST use a pH meter if you're going to do this. It's too easy to overdose. I dissolve a couple of tsp of citric acid in a cup of water, and add 4-5 drops of this concentrate to my 2 L jug of water. Doesn't take much.

[Vanda lover]

Thanks ALTORONTO, this is useful info.