Growing medium

Rodger Whitlock
Wed, 11 Jul 2012 17:01:07 PDT
On 11 Jul 2012, at 8:49, Bulborum Botanicum wrote:

> How do you sterilise larger quantities seeding mixture

I can tell you how the City of Victoria used to sterilize potting soil: on a 
large concrete pad, they'd lay out lines of 6" drain tiles (probably terra 
cotta), pile the soil over those, then pass steam through the lines until the 
entire pile was steaming.

This wasn't sterilization in the strict sense. It's really pasteurization, 
killing off most seeds, pests, and microbes, but leaving some microbes alive.

I suspect, but can't say for sure, that they mixed John Innes type potting and 
seed composts where the additives (lime, fertilizers) went in *after* the soil 
had been pasteurized.

A simpler system for smaller quantities: put your damp soil in black plastic 
garbage bags and leave them in the sun.

Rodger Whitlock
Victoria, British Columbia, Canada
Z. 7-8, cool Mediterranean climate

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