Dirt will eventually work its way back down under the gravel even if it does get pulled up. Small particles work their way down under big particles. There is a good physics reason why that is always so, but I don't know the details. And, you can also just cut off the plants at the substrate line, and leave the rooted stump to disintegrate on its own. Some of my plants have been able to work their way up out of the substrate by themselves, so clearly you can slowly pull many plants out without a cloud of dirt following them.
Last edited by Hoppy; 08-13-2012 at 05:09 AM.