Most "weeds", and their seeds, are not killed by the heat of a compost pile but simply because the compost pile keeps those plant from getting access to the sunlight they need to grow, provided those plants are buried in the compost not just thrown on top. Sometimes those plastic bags work but other times they only provide a really good place for those plants to grow.

so, if it seems like sunlight is the primary issue (which it really may be in this case, as this is a plant people actually pay for -- I can't think of the name, its a succulent that I've seen in plant catalogs -- its just hard for me to get rid of), then perhaps just making this a bottom layer of a lasagna garden bed might even be ok?

That's the other problem with my pile -- its hopefully not going to be a big ol pile much longer, but part of a lasagna garden bed....

I did something similar as the poster of this thread - threw chunks of sod riddled with Wild Violet into black trash bags thinking that after a few weeks they would be dead and I could re-claim the soil. This material has been laying in closed (thought not tightly sealed trash bags)since March. When I open them up and dig through the sod I still see viable Wild Violet shoots though everything else is dead. We haven't had many hot days yet though. Because these trash bags are kind of an eyesore I wonder if there is anything I can do to speed the destruction of these plants/weeds. I would like to save the soil they are in - otherwise I would discard it somewhere out in the woods. Would it be faster to move the bags inside of my garage with dim light? I guess the question is whether plants die faster due to excess heat (but some minimal light penetrating the bag) or due to a lack of light (but less heat). Thanks for any suggestions.

I'm researching this now. I read that heat resistant weeds need a minimum time at a high enough temperature to be made infertile. Seems 140 degrees is a good temp for most, but 200 degrees can be too high. If you look up solarization, 6-8 weeks during the hottest time of the year is their recommendation, which works against the best gardening time except for prepping an area a year in advance! Moisture is also useful. In solarization, clear plastic traps more heat than black, so it could be useful to compare that; and I'm thinking of trying adding water to bags of weeds and turning them throughout the summer. I guess putting the result somewhere to see if it sprouts next year would answer this question! (I live in the desert, so high temps are easy here. Might not work as well elsewhere?)

I have done something similar with English Ivy. I have a lot I should pull up, but it's a major task, and so far I'm just keeping it somewhat at bay. When I pull it off the stone wall out front a couple times a year, I've bagged it and left it sitting. It may have been winter, and I may have put it in a shady spot, but that stuff takes a LONG time to die. If I pull it in smaller quantity, I have been known to leave it in the sunny driveway to die (which still takes a while). I won't put it anywhere near compost or ground where it could re-root, until it's thoroughly dead.

I could put it in the trash, but it would fill the can for the week. I'd rather tuck it in a bag out back and eventually return it to the earth, but not until it can't re-root.

My Master Gardener friend suggested adding water to the garbage bag so that the stuff inside would rot. I suppose you would need a black bag to keep out light or things might just grow inside like they were in a terrarium! Not a problem where I live--with dry desert and super hot summers. I can imagine Boston Ivy being able to make a break for it and poke through a bag, maybe? Anyone actually tried this?

Several years ago I was told that putting Quack Grass in black plastic bags, sealing them, and leaving them lie about in the sun would kill that Quack Grass. It did not. That grass grew inside those bags and punched their way out with, apparently little trouble.

I have not done that with Ivy but someone else did and found the same thing.

kimmq is kimmsr

Try clear plastic trash bags tied at the top - much more solar heat gain. And if you double the plastic bags, leaving a gap, this works as insulation, making the contents of the interior bag much hotter.

I did this last fall to sterilize plastic nursery pots. Ended up melting half the pots.