The established raspberry bed that I inherited with my allotment is full with canes all over the place in no particular lines. (I guess they may be autumn then, as there is no post and wire support system in place?) Tbe bed is about 17ft x 10ft. All the canes have been cut down to ground level. Every bit of soil around the canes is filled with couch grass. I could sit and patiently dig out every piece but the canes are so close together that this would be extremely difficult. Is the answer to simply cover the entire bed (cut down canes and all) with a 6 inch layer of compost? Cardboard would be difficult to lay as it would kind of ‘sit’ on top of the old woody canes, instead of directly on the soil. Any help much appreciated!
Yes I would do exactly that. You could remove some suckering raspberry roots to plant in another, clean bed. Meanwhile the mulching is well worth it compared with weeding couch grass every year, as you would never be able to remove more than a half of its roots.
And yes black polythene makes most sense, well secured/weighted at the edges as the raspberries will push it up at first, until they run out of reserves, as the couch grass also exhausts itself, over the course of a whole season: it should be 95% gone by winter. Then any remaining roots can be pulled out or levered out with a trowel, and keep an eye out for a few stragglers in 2013 to have soil 100% clear.
Of the two types of bindweed, hedge and field (white flowers, thick rooots for hedge and pink flowers, thinner roots for field) you can almost (say 95%+) get rid of hedge bindweed in a year with 100% light exclusion. Field bindweed would be massively weakened and subsequently controllable with a trowel.
So yes I would cut to the ground and mulch, preferably black polythene as bindweed sneaks out the overlaps of cardboard.