Ahh, that is a relief. As my containers are already filled, I thought I had missed the boat with not putting light weight bulk at the bottom, but just as well I didn't. Good to know. Ina Ina Crossley Auckland New Zealand zone 10a On 4/12/2013 9:10 a.m., Ellen Hornig wrote: > Thus putting coarse material at the bottom worsens drainage in the > root zone, because it pushes the saturated zone higher. The only thing it > does achieve is to make the container lighter (assuming you use cans, or > chunks of Styrofoam, and not rocks).