Square foot gardening and vermiculite

[Springfever]

I have just recently gotten Mel's book and I have some questions about vermiculite. Is it safe and is this a good method of gardening. After 2 years of weeding and hoeing a filling this sure does look like something I'd be willing to try. Any comments please.

[tomc]

it lightens soil a little. IMO not a particularly cost effective way to lighten soil. I'll keep on wiht compost I can forage instead.

[imafan26]

The Libby vermiculite mine in the US was closed because of contamination by asbestos. Vermiculite is a metamorphic rock found all over the world. Vermiculite today is mined from areas that are not contaminated and is safe.

Vermiculite is light, holds water and provides a good substrate for holding roots. Perlite is a little cheaper than vermiculite and does the same thing. Both vermiculite and perlite are used to root cuttings and in hydroponics.

Mel's mix does use vermiculite, you can also use coarse builder's sand but it is quite heavy. Perlite can also be substituted as well as crushed cinders. All of these things help with drainage, are long lasting and don't pack down. Compost does improve drainage and water holding capacity, but I have had issues with mixes that contain more than 20% compost, because compost does continue to break down and it compacts.

Because perlite and vermiculite do not breakdown and compact, you usually only have to put it in the initial planting mix. After that you only need to add compost.

[applestar]

There was a long thorough discussion about vermiculite and perlite a couple of years ago. I'm on a browser right now that won't let me use the search function.

[DoubleDogFarm]

Here's one in 2009

https://www.helpfulgardener.com/forum/vi ... hp?t=18177

Eric

[ElizabethB]

The trick with vermiculite is to find and use horticultural vermiculite. A little courser than regular vermiculite. I find mine at a locally owned feed store. The store started carrying horticulture vermiculite to meet the demand from Master Gardeners. Good stuff. Perfect for Mel's Mix.

[rainbowgardener]

The idea of the perlite / vermiculite is mainly to keep your soil mix from packing down, especially in containers/ raised beds, and to keep spaces for air and water circulation. You can substitute coarse sand, crushed granite, crushed lava rock, styrofoam pellets, chopped up corn stalks, pine bark bits, rice hulls, crushed pumice, peanut shells.etc.