Thanks for the link Lynn. That is exactly along the lines of what I decided to try. In fact, I had even ordered some sphagnum moss yesterday!
Here's what I came up with. I'm going to make a giant chicken wire ball with several layers of chicken wire. We have bags of those styrofoam peanuts at work, and I'm going to fill the ball with those (not the kind that dissolve with water!
) I'm going to cover the chicken wire with a thick layer of sphagnum moss, about 3" thick, and that's it. I'm not using any potting mix. I figure there isn't any potting mix in the wreaths I make, so I probably won't need any for the giant ball. After all, the roots will probably never get totally through the sphagnum moss anyway. And it's not like it will have to support any weight besides the plants. Like the wreaths, I'll just water it with a Miracle Grow solution every month or two. I'm going to put it in an area of the garden where it should get full sun and figure (hope) that it probably won't need turning. So, think that'll work?