I'd be reluctant to try what you're thinking of doing. I've had black plastic and clear plastic over a small section of weeds for over a year, and there's still nice green weeds coming up under there.

If your experiment doesn't work, you'll have the invasives in your compost and your own yard. Yikes! People who have experience with really hot composting I'm sure would do what you're proposing, but if you don't hot compost, you may be in for trouble.

My Two Cents for What They're Worth.

I think I will cautiously try it. The difference, I believe, is the conditions you are providing simply limit light-ordinarily quite effective!

The trash bags combined with excess moisture provide anaerobic and hot conditions.

Theoretically.

But since it is scary to think of purple loosestrife loose in my yard I will have a test bed for the compost :-) and be ready to use the flamethrower if I must!

-P (frightened but wilful)

I once made compost, accidentally, from a black plastic garbage bag of leaves. I forgot it under a woodpile for 2-3 years and when I dragged it out it looked like a purchased bag of topsoil. There was not a trace of debris. Interestingly, it was also full of ants. I would give it a try, it should work. Maybe with the first one you could open the bag next year and monitor if anything sprouts in it before you use it?

I've had the same experience as northspruce, first by accident, and then on purpose. Only mine wasn't leaves, but the weeds I would not ordinarily toss in the compost pile...dandelion roots, fireweed roots, bird vetch, linaria vulgaris, and last but most importantly...horsetail roots.

Gah horsetail. I have a huge yard--almost totally empty at the moment. DH broke the riding lawnmower too, so I have to stuff black garbage bags full of weeds on a daily basis, in between borrowing a push mower from my best (and most wonderful) friend. I figure, what the heck, I'll compost weeds and use the black bags as winter protection for the perennials I've been putting in since we bought the house. The prospects of compost makes the weeding easier on the soul, lol! I'm piling the full weed bags in a corner, and will use them in fall to encircle the new perennials . I don't have enough trees yet to use leaves :-( So I figure I can afford to let the weeks marinate for at least a year if not more before I dump them in a quarantined compost pile.

I ok'd the purchase of this house based on the great sunlight and the huge lot. But we bought it in winter. I didn't realize the contractor had not only done the typical sod stripping but also graveled almost the entire 2 acres!! So weeds pop up everywhere in the gravel, but can't be mowed, and the lawn is patchy and vulnerable to invasives and weeds due to the crappiness of the soil. Weeding at the moment is like when in fall we have that abundance of zucchini we can't PAY people to take. I'm desperate to find a use for them so I don't feel the futility of my weeding endeavor. Even though I'm improving the soil, it will be years before the weeds are under control. (if that can ever REALLY happen, LOL)

So, following everyone's advice very carefully....

-P

Back in Switzerland we had a school garden and all the weeds
got tossed to the compost...hm, my dad's compost got weeds
too but some of the nasty thistles got burned.

I've put various weeds in black plastic bags and left them in the sun and within a couple of weeks they are done for. It's an anaerobic process so they are a slimy stinky mess but IMO safe to compost. For really dangerous weeds that have gone to seed I'd leave them longer as seeds can sometimes survive longer even in inhospitable conditions.

Right now my weeds are decomposing in a pile under a black tarp. Plants require light to survive. I don't compost thistles as they take longer to break down and I prefer not to be stabbed. They are pulled with leather gloves on or weed whacked and left out in the back 40.

Good info!

I've got 4 drum liner bags filled with the bad types behind my apple trees in full sunlight so far.

arcticiris- how did it go? It's been a few years since this post, I'd love for an update!

Thanks!

We have a large lot (and a similar gravel situation) and would be more than happy to bag the weeds and let them sit a year or more in a sunny spot, if we got compost someday from it, and killed the weeds! We can't afford to buy compost, and can't afford yard waste, so it would be a great thing for us to try!.