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  • From: yarrow@sfo.com
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: [permaculture] weed seeds, was Re: Tending the Wild, Wood Ash
  • Date: Mon, 18 Dec 2006 12:06:28 -0800

I haven't heard of devices that burn out weed seeds, but I'm skeptical.

I have heard of solarizing for "burning" out some weed seeds, and yes, it does also bake out beneficials in the soil. But it affects only the top layer (exactly how deep depends on how hot the summer sun, duration the plastic stays on the soil, moisture level, type of soil, etc., as well as prep work before laying down plastic sheets -- till, water, till again, water again, to force germination of as many weeds as possible), so if you then disturb (till) the soil, you may bring up more weed seeds.

Flame weeders and burning are totally different techniques, though.

The purpose of flame weeding is to heat up weed tissue enough to cut off circulation, so that the plant eventually withers and dies. In other words, the plant is heated just enough to damage it, not scorch it. The best time to use it is when the weeds are lush and green -- you don't want to use it on partly dried (flammable!) weeds. I've heard about steam weeders that do the same thing.

Myself, I'd rather pile on the cardboard/newspapers and mulch. So far, in the relatively small areas where I've worked (less than 1K sf), this has been sufficient to get rid of bermuda grass, bindweed, and mallow within a season.



At 11:44 AM -0800 12/18/06, Rob Kelly wrote:
Just last night I was talking with a friend who
was curious about "fire weeders" -- propane
powered contraptions that you use to burn out any
weed seed. (You wheel along like a vacuum and
everything under the hood gets torched.)

I wondered whether such heat also killed
beneficials in the soil, or whether those deeper
in the soil quickly repopulated the top layer
that was burned.

Now that I think of burning as a tried and true
technique, I wonder again whether these fire
weeders, propane consumption aside, are a pretty
good idea.




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