While normal cold composting, using a one year cycle, may not kill the roots of perennial weeds composting in a covered heap, from which the light is excluded. A period of two years has been reported as being effective for many perennial
weeds. Turning the heap raises the temperature and will reduce the number surviving .
Charles Dowding https://charlesdowding.co.uk/advice-on-making-compost/ composts perennial
weeds, including bindweed, docks, nettles, buttercups, dandelions and couch grass in a layered bin turned once. Weeds with soil on their roots can be included. The weeds will break down even in winter’s cooler heaps and regrow only if left
exposed to light.
When I took on my first allotment plot it was covered in perennial weeds and I took the lazy approach of making a pallet bin using four pallets, filling it with weeds, turning it just once when the bin was full and leaving it,
covered, until some of the pallets rotted. Although there were a few roots struggling to survive on the surface where some light had seeped in, the compost was excellent.
When using this and any other method of treatment on this page it is recommended
to check the compost at the end of the treatment to ensure the absence of living roots before use.
ASK Organic (http://askorganic.co.uk/composting/perennial%20weeds.pdf)
recommend using a separate plastic compost bin so as to ensure that all light is excluded which may not be possible if using a wooden bin. The material is kept covered in the bin for two complete years to rot down.
weeds are growing in turf or grass which must be cleared, as may be the case when taking on a new or neglected plot, a turf stack can be used. The turves should be lifted and neatly stacked green sides together. The stack is then covered
by a black plastic sheet and left for up to two years by which time they will have rotted down to form a quality topsoil. This method can be used successfully to deal with couch grass.