I keep thinking to fill the vase, stem part of the mushroom with small stones. Then the weight of the stones would hold it in place in the garden or you would have to glue a stake of some kind on the bottom. I have a vase and top picked out to try it and see what it looks like. I also have some plastic stakes with flat tops that might just work well. I am going to a plant swap next weekend and it might make a nice gift. Guess I need to see about a bag of stones.
