i have had another stump in the first setup and it did get very soft just by brushing against it i'd have a for lack of a better term shaving would come off of it but this stump you see now i decided to go against the rules and try a cedar stump. while i agree using a green/fresh cedar stump probably is not the best idea as cedars have a lot of oils in it. This stump i used was one that had fallen over and it appeared to be at least a few years dead. This stump has held up very well no noticeable decay can be found even the part of the stump thats out of the water with a plant growing on it has't fallen apart yet. As i drilled out the top for a good 6" or more and placed rocks in it to help hold down the stump and soil to allow for plant growth.