I had that problem last year when I tried keeping a small amount of water in the bottom of the pan. My hope was that the cardboard would wick the water and the soil would wick off the cardboard. Good in theory....except that the cardboard disintegrated after 2 weeks of sitting in water.As much as I love the TP roll idea, it never actually works for me. Either the cardboard wicks all the moisture from the soil, or I have to keep it so wet that the cardboard disintegrates.
This year I tried to be smarter.... I put a bowl of water in the center of pan but did NOT put any water in the pan itself. I do spray a little bit of water in the tp roll to ensure that the soil stays moist but I don't saturate. Then I covered the pan with a clear top to contain the humidity. This method has really helped to keep the tp rolls from disintegrating SO FAR. We'll see what happens over the next few weeks. I might have to come back and eat crow....
