Lots of people say blanket and duck weed should be put on the compost heap. Just turned over a year old, well looked after heap, which has been banked up with earth and has plenty of soft material in it, so ideal composting conditions. We discovered none of the pond weeds had rotted. Not such a good idea after all.
However, we’ve increasingly used the pond weeds as mulches to keep the roots of plants damp and to wipe out weeds, and especially the reeds that are trying to conquer the edges of the pond again. So the pond is producing a useful product after all.