Michael Mace wrote about possible effects of rotting wood underneath his bulb pots. I have always avoided using bark or other wood products in my bulb-growing mixes because I felt that the fungi that decompose the wood might also attack the tunics of the bulbs and other non-living tissue that is still important to the plants. I know some people think this is silly, but it has worked for me for many years. It's difficult to buy soil mixes that don't contain bark and sawdust. When living in the country, I had a source of excellent natural humus (admittedly, full of microorganisms) that made up a quarter of my bulb mix. Now I'm growing them in pure coarse sand with a layer of ordinary soil down below, and pea gravel on top. I do have to fertilize them several times during the growing season but they appear very healthy. Jane McGary Portland, Oregon, USA