Killing weeds in compost

rutgers1(6NJ)September 28, 2007

I have a lot of weeds in my compost bin. I hope that I got the temperature high enough to kill the seeds, but I am not sure. I was wondering if spreading out the compost on my driveway next summer for a few hours would do the trick. The driveway gets REALLY hot, and I wonder if they would bake into oblivion there.

Are there any quick-hit ways to make sure the weed seeds are dead?

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Even though you may have put "weeds" in you compost unless you are sure they had seeds there should be no problem. Most all growing season I have "weeds" to add to my compost but I make sure the few times they may be present that any seeds or seed heads are not included. Like any other plant it takes time for "weeds" to produce seeds so the simmple presence of some does not mean there are seeds.
Spreading your compost out on the driveway is a lot of unnecessary work.

    Bookmark   September 29, 2007 at 7:31AM
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When I add problem weed or stuff that is likely to have seeds, I try and make sure to add them into the hottest part of the pile so that they will get a proper heat treatment since as we all know, the very outside edges of the compost pile/bin never reach the high temps. One method I have for doing this is I drop the seed heads into the bucket that collects kitchen scraps. I always try to bury anything that can get stinky in the hottest part of the pile anyway.

    Bookmark   September 29, 2007 at 9:48AM
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katielovesdogs(z5b/6a Indiana)

I throw weeds and some seedy weeds into my compost. I just make sure that I sprinkle corn gluten on the top of compost after I add it to my garden. The corn gluten retards seed germination.

    Bookmark   September 30, 2007 at 9:44AM
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ceresone(missouri ozarks)

What does the corn gluten do to the seed you PLANT in the garden?

    Bookmark   September 30, 2007 at 12:39PM
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Unless you are very careful there usually will be some amount of weed seeds, tomato seeds, squash seeds, and so on in your compost. I doubt that the heat from the concrete would be enough to kill them all unless you put clear plastic tight over it. With enough hot sunny days that would probably do the trick. I agree, it does sound like a lot of work, plastic or no plastic. I keep one clean pile and everything questionable (weed seeds, potentially diseased, slow to compost) into another pile. I've been pondering what to do with the latter when, after another season or two, I finally stop adding to what is becoming an enormous windrow. I may add it all to one bed that will always be covered with plastic or a thick layer of organic mulch. The weed seeds must number in the billions by now.


    Bookmark   September 30, 2007 at 9:56PM
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Thanks for the responses everyone.

Katielovesdogs....I don't think sprinkling corn gluten will have any effect. As far as I know, tests done with corn gluten have focused on crab grass, and there has to be a LOT of it to work. And, unless I have missed it, they have all centered on crab grass seeds in the lawn. We have actually had some discussions on this in the organic lawn care forum. I am in the camp that believes that the success with corn gluten has more to do with the fact that it is a great fertilizer and therefore promotes a healthier stand of grass that crowds out crabgrass, rather than it having preemergent qualities.

    Bookmark   September 30, 2007 at 10:13PM
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Corn Gluten Meal will, if properly used, stop the germination of many "weed" seeds, but lots of people have formed opinions of it with little knowledge of the product. This link to the Iowa State University research page on CGM may help you understand what it does.

Here is a link that might be useful: Corn Gluten Meal Iowa State

    Bookmark   October 1, 2007 at 7:17AM
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Those seeds that have sprouted and come up allowing you to know that they are there are done for if you just turn the weeds under before they make new seed. In fact, if there are others in there, they may have already been killed by heat if your compost heated up enough, or, if turned up near enough to the surface will also sprout come up and expend their efforts befoe going into the garden.

You will practically always have some weeds come up in the garden. Many are in the soil waiting until conditions are right for them to sprout, (like being turned up near the surface), they blow in on the wind, wash in on the water and are spread by birds. If you pull them, hoe them or disrupt them by some kind of cultivation while they are little, they usually do not cause much of a problem. A good layer of shredded leaf mulch or hay as mulch will also help a lot to keep weeds down, while conserving moisture and keeping the soil temperature at a more stable level.
Just my .02
Bill P.

    Bookmark   October 1, 2007 at 9:49AM
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PaulNS(NS zone 6a)

With a very few exceptions like velvetleaf seeds - according to what I've read these are hard to kill through composting - but then I've never come across the plants - weed seeds will germinate and rot in the moist warm darkness of a compost pile, or for that matter the moist cool or cold darkness. Conditions for germination are bad for growth. Important thing is to keep a good cover of 'browns' on the pile. Composting for a long cool time will do the same job as composting fast at high heat. This has been my experience. As usual, the cheap, lazy way of doing things is the best.

    Bookmark   October 1, 2007 at 9:49AM
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