I have two full bags of pulled bindweed with roots and a barrow of grass that flowered before I got to it. My pile is a two bay pallet setup that gets hot for a week after a big build and then coasts. I would rather not send it all to the tip if the pile can handle it. Where is the line between a weed that is fine and one that comes back?
I would warn anyone about the smell before they try the bucket method, because it is genuinely appalling and it will be somewhere near your washing line for six weeks. I bag perennial roots in black plastic in a sunny corner for a season instead, which is slower and much less offensive to live with.
For perennial roots there is a reliable low tech answer: drown them. Bindweed, couch grass and dock roots go into a bucket or a lidded bin of water for a month or six weeks, by which point they are unrecognisable sludge that composts safely and makes a decent liquid feed if you dilute it hard. No heat required and no judgement calls.
For what it is worth, I composted couch grass roots years ago on the assumption the heap would deal with it and I spread that compost over three beds. Two full seasons of pulling it out afterwards, and I still get it along one fence. That single decision cost more hours than every other gardening mistake I have made put together.
Two seasons of pulling it out afterwards is the warning I needed, because that was very close to my plan for this weekend.
Couch grass and bindweed punish this specifically. Most other perennial roots do die in a heap that gets properly hot, which is why the advice sounds inconsistent.
Annual weeds before they flower, straight in. Seed heads and perennial roots, out. That line has never let me down.
Worth remembering the municipal option is not a defeat. Their process runs hotter and for longer than anything you can do with pallets, so the bindweed goes in the council bin and comes back as somebody's soil improver rather than as your problem.
@drip_dana · 3mo ago · 3 replies
The figure that gets quoted for killing seeds and pathogens is around 55C held for a few days, with turning so that the cold outer material spends time in the middle. Your pile probably hits that in the middle for a week, which is why the middle is fine and the outside is not. In practice a home pile kills most seed in the core and almost none at the edges, so unless you are turning aggressively and monitoring temperature, assume seed heads survive. Perennial roots like bindweed are a separate problem, because a single fragment is a new plant.
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@cue_carla · 3mo ago
The edges being a seed bank makes sense of why my worst weeds appear exactly where I spread the compost.
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@broody_bess · 3mo ago
That was my experience too. Middle of the heap was clean, the crumbly stuff off the sides was a nursery.
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