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