Can we use real mulch (large wood chips) as part of the layering for our lasagna 'garden'?--it is really an area in which we will be placing hostas and bushes. We layed newspaper down last year in area that we wanted to kill the grass and then placed mulch over it temporarily because we could not proceed with our layering/ landscaping (we live in the town that was hit by the Nov tornado so we had other issues to deal with last fall). Do I need to dig it up, or will it suffice as one of our "brown" layers? If, I do have to clear most of it would it be ok to use it pile up along with a large amount of grass clippings to make a small berm?