Catch 22 Composting

[Ridgerunner]

Or, do the weed seeds die in the compost? If so, any idea how long that would take? Thanks everyone.

If the weed seeds are in the middle of the compost when it heats up they will get cooked. I don't turn my pile that much and when I do, all the weed seeds do not wind up in the middle. If you have a barrel composter and you turn it a lot you will probably be OK. I personally would not trust turning a pile to really mix it that well, but the more often you turn it the better. After a while it doesn't heat up that much as the percentage of uncomposted material compared to composted material isn't that high. How well it works will be in the details, how and how often you turn it. In theory it works. In practice you have to work at it harder than I do.

I try to avoid putting noxious weed seeds in the compost pile. For example, Canada Thistle and nutsedge goes straight to my burn barrel, the whole plant - roots seeds and all. Diseased garden plants or plants infested with certain pests do not make it to my compost pile. But about everything else does. I have volunteer tomatoes, zinnias, and marigolds popping up, among other things. It takes work to control them but I think the compost is worth it.

 

[Old Philosopher]

I encourage everyone to go on YouTube and search for "drunken compost". I tried that for the first time this year, and had usable compost in 3 weeks..... Seriously.

 

[IamRainey]

130˚ is the target for killing most weeds. For the worst ones you need 145˚ for 30 days. That's why I throw all my nutsedge and bermuda grass in the trash instead of composting it. But with conventional composting you won't get any more weeds than usual.

I, personally, do the largest piles I can so that the mass generates heat. I don't believe the conventional 3'x3'x3' commercial enclosures really do the job unless you're scrupulous about things like ratios, watering and turning. That's how I started out and what I got was really better described as mulch. I was thrilled about it at the time, of course, but my big 4'x6'x4' piles produce actual humus -- passively -- and, while I only occasionally monitor the temps these days, that kind of mass is capable of those 145˚ and higher heats.

 

[PANEAVES]

Please let me caution you about using coffee grounds. Make sure they are well mixed into your compost before walking away. We had a small heap of grounds left on top of a pile and one of the dogs came by and took a large bite of grounds. We didn't know that coffee grounds are toxic due to the amount of caffaine they contain. Later that night she became very ill. We thought she was going to die. Fortunately, between diarrhea and vomiting episodes she drank a lot of water and that pulled her through. We had no idea this was connected to the grounds until I happened to remember her eating some and looked it up on the internet. I have spread the word to anyone I know who had dogs. Please be careful with your grounds!

 

[IamRainey]

Thanks for that word of caution!

As someone whose lab ate a 17oz. 72% cocoa bar once and who watched her heart beating in her chest, I know what you're talking about. I hope people will heed your warning!

 

[ChocolateMouse]

Another take, is the weed seeds do a few things in compost piles.
First, in a good pile most of them will die to heat and decomposition. A good pile gets hot.

Later the ones on the surface especially will germinate early from the extra heat produced by the compost. These ones get mixed back in and actually just add to the pile.

Later the last few tell you when the compost is done. Active compost has compounds in it that prohibit germination, which is part of why you don't want to add these things or fresh manures directly to the garden beds. The germinating weed seeds on top of the pile after the heat is gone says those chemicals are gone from the compost and it's safe to be added.

Lastly, some few weeds DO sprout in the garden beds. But for me this just means they get dug back into the garden bed as further nutrients later.

I don't actually mind weeds as long as you don't let them go to seed in the beds as they serve a purpose.

 

[IamRainey]

How interesting and helpful, ChocolateMouse. I'm printing that out and saving it and, of course, I'll watch for signs of it in my piles.

 

[ChocolateMouse]

https://articles.extension.org/pages/28585/composting-to-reduce-weed-seeds-and-plant-pathogens
This is a pretty OK article on it. Basically, seeds germinate on the surface from heat, but have trouble because of how bioactive the compost is. Those get stirred in and most die off. Once the heat is gone, the compost needs to sit a little longer to finish out. Then I start to get a second round of seed sprouting that is more successful and I know the compost is very well finished and stable.

 

[jthornton]

This sure is a good thread on composting...

JT

 

[IamRainey]

Yes! Tons of good information and a variety of approaches.