Kiln dried block paving sand?

[ralphrmartin]

Mike

I've got 2 sizes or vermiculite, seed grade, and "regular". if you look back a few years, there was quite a bit of talk about vermiculite denaturing and disintegrating in compost, over time. Now, that doesn't matter in a seed compost,as I reckon to pot seedlings on after 6 months anyway, so the vermiculite doesn't last long enough for much degradation - and anyway, it probably doesn;t matter for seedlings which like it damp. But I leave adult plants in the same compost for 3 years (unless they outgrow their pots), which is definitely long enough for the vermiculite to break down. Essentially it ends up as mica sand, or smaller, so holds much more water. That's the basic gist of it, anyway.

Ralph

[colser]

Thanks Ralph, very useful