Mary Sue referred to using mushroom compost one year with disastrous results. I used to build whole beds with it, mixing it with our native clay soil. It added wondrous tilth. About three years after the first bed, every daffodil planted in it was gone. Another year, the daffodils didn't even come up the first spring in a new bed with mushroom compost. The horticulture head at our huge Spring Grove Cemetery here in Cincinnati told me that when they add soil amendments, they always send samples to a lab for analysis first. He had a batch of mushroom compost that came back with the analysis that it was so full of salts it would not support plant life. Of course I no longer use mushroom compost. Bill Lee