It will only kill the bacteria in the part of the pile at and near the surface where it was applied. The deeper bacteria in the pile should be just fine.

The pile should be able to regenerate it's "good" bacteria quite quickly...especially with the soil warmed up.

By the time the water hit the compost and reached any weed seeds I should imagine it would be well below boiling. And how were you going to deliver the water? A stream from a kettle would be far to little. For the same reason it won't hurt many bacteria it won't kill many seeds.

The description I read was at the attached link. The author keeps compost she's going to use soon in a 5 gallon bucket right outside her kitchen door. She takes the water straight from the stove to the door and dumps it in immediately, leaving it to cool overnight. It sounds as though it would work for weed seeds, and from what's been said here, it sounds as though a few bacteria would survive and repopulate in the compost quickly. Does that sound accurate, or does the bacteria in compost not matter that much?

Here is a link that might be useful: FAQ about using compost in winter sowing

OK, so she's adding boiling water to *finished* compost rather than during the composting process.

This won't hurt the nutrients and organic matter content, but it sure will knock down a lot of the microbes. The role of compost microbes should not be underestimated. I don't think I would do this on compost I was going to use in the garden.

BUT the link is about using it for seed sprouting, which is commonly done with a fairly sterile mix to avoid diseases. Once the plants are established they get repotted in soil or regular potting mix. I don't think it's much of a problem to wipe out microbes in this case.

Gotcha! That makes absolute sense. Thank you.

That's the first time I've done *that* in a long time...ask anybody. :-D

Pouring boiled water on compost is meant to sterilize that compost and that means killing any bacteria that are in that compost. Water that would be hot enough to kill any "weed" seeds will also kill off any bacteria, good, bad, or indifferent, in that compost. Most "weed" seeds can be rendered inert at temperatures much lower that 212 degrees, and at temperatures that will not harm the bacteria that are needed in that compost.

Here is a link that might be useful: weed seeds

The point of the article referenced by leggs was to produce a clean (sterile) compost for use in a seed starting. In that specific case, killing everything is typically the desire. Soil sterilization is nothing new.

Hmm, "sterile compost" makes as much sense as "fat free half and half". By definition, compost is teeming with organisms. Frankly, I can't see why you'd ever want to sterilize it. The organisms are so beneficial for plant health, why would you wnat to sterilize it to use as a seed starting medium? It's like nuking your yogurt before you eat it!

Seeds/seedlings contain their own nutrients. Most people who use compost as a seed starting medium care more about possible pathogen contamination over the nutrient content of the soil. If you're pulling the seedling to re-plant after 1-3 true sets of leaves the only additions to the soil that really matter is growth/rooting hormones. A booster of chemical fertilizers will speed things along a lot more quickly than the nutrients in a low-and-slow availability compost.

I wouldn't advise seed starting in compost anyway. IMO, it's a waste of good compost that could be better utilized in a long term planting scheme (especially in-ground native soils).

Excellent information! Thank you all so much. I have noticed weeds sprouting in the plots on which I use my compost. Is there a good way of eradicating weed seeds or do you just make sure you pull the weeds while they're still tiny and easy to spot? I suppose I could just stop using weeds in compost, but unfortunately, weeds have been one of my major green sources this year. (Working on changing that!)

Weed seeds will always be everywhere. The way to kill them in compost is to get it hot enough to reduce the seeds' viability. So you turn the compost, you leave it sit, you water it, measure the temperature, and some of the seeds will not germinate if you can get it hot enough and keep it that way until it's "soup". But more seeds will blow onto the pile, guaranteed. Don't let that stop you from using weeds in your pile if you need green material. If you want to go ahead and snip off the seed heads, fine. I don't bother. I get so many weeds in my garden beds as it is, even without adding my homemade compost.

Composting is the most natural process in the world, and sometimes I think we humans make it way more complicated than it needs to be. Weed seeds are everywhere. Surrender to that, LOL!

Weed seeds will always be everywhere. The way to kill them in compost is to get it hot enough to reduce the seeds' viability. So you turn the compost, you leave it sit, you water it, measure the temperature, and some of the seeds will not germinate if you can get it hot enough and keep it that way until it's "soup". But more seeds will blow onto the pile, guaranteed. Don't let that stop you from using weeds in your pile if you need green material. If you want to go ahead and snip off the seed heads, fine. I don't bother. I get so many weeds in my garden beds as it is, even without adding my homemade compost.

Composting is the most natural process in the world, and sometimes I think we humans make it way more complicated than it needs to be. Weed seeds are everywhere. Surrender to that, LOL!