perlite vs lava rock

[weederwoman]

I have a ready source of large pea-sized perlite. How would this differ from the lava rock people in this forum talk about so much. Also, if I try using expanded clay balls as the sole medium, is it best to add perlite (or lava rock) to make more irregular air spaces. The balls seem to fit together pretty tightly because of their symmetry. Thanks

[Bloomin_Aussie]

In terms of aeration there's probably not much difference however lava rock will provide trace amounts of minerals at the same time. As for LECA I would think it would be ok by itself... the roots will push the balls apart by themselves.

[Leafmite]

Lava rock is nice because it doesn't float out of the pot (at least, most of it doesn't). You can break lava rock up into smaller pieces. I don't know how it compares to LECA as I haven't tried it yet. I am thinking of buying some of the smaller type to replace the NZ sphagnum moss.

[Vanda lover]

Perlite is so light that it does float out of the pot. It is great for adding to other mediums such as coconut chips or moss. Lava rock wicks very well, in fact I think it wicks better than Leca. I have used both for s/h. I have several plants in s/h in lava rock and they love it.

[nutgirl]

I use both LECA and lava rock depending on the plant.

So far, I've used large lava for things needing good air flow and drainage such as Vandas.
I use LECA for pretty much everything else since I like to water all my plants at the same time. There does not seem to be a problem with air spaces. It drains fast and leaves a nice humid environment for the roots.
I also break my lava into smaller pieces as Leafmite said so it is probably more practical and cheaper to use than LECA.

Maureen

[dounoharm]

as far as the difference between the two, lava rock is the actual remains of the hardened lava....perlite is a substance that is derived from a sort of lava rock that has been pressurized and expanded to include more air in the actual product I believe. it is used extensively in soilless mixes to aerate the mix, (vermiculite which is similar in some aspects to perlite, is created by pressurizing and expanding mica rock)...it is also used in bark mixes with orchids to lighten and aerate the mix...it is a matter of preference as to what media you use...whatever suits your style and environment....good luck!

[ALToronto]

Lava rock is heavy enough to hold in the roots and keep the pots from tipping over.

[Ray]

And...the assessment that the regularity of the LECA makes it pack too tightly is actually 180° from the truth.

100% perfectly spherical, identically-sized particles provides the most open volume - about 40%. Any irregularity or mixture of sizes actually reduce that open volume. It may not "stack" that way initially, but it will ultimately settle into a denser medium.

Interestingly enough, no matter what the size of those spheres - basketballs or BB's - the open volume is identical. However, the smaller the spheres, the smaller the voids, and the more likely that surface tension will hold the water well enough to completely block all air flow, suffocating the plants' roots.

[weederwoman]

Thank you. I will need to find a local source for the lava rock that is as reasonable in quantity and price as the perlite. It is used here in Oregon by the ton to spread on the icy roads, but I fear the stores will only have pricey little bags. And thanks for the info on the expanded clay.

[nutgirl]

My local Orchard Supply sells the red lava rock in large bags. The price wasn't too bad, can't remember what it was.

Maureen