Dave-
I am not sure about the longevity of this method seeing as how we just tried it, and it would probably be a bit costly for a big job of 200 trees (we only did 4)...but here's what we did:
First we took old tire rims (ours were 4 rims off an old ford pickup) and inserted the trees upright down through the middle of the rims. Next, we drilled two holes near the base of the tree about a foot apart, so one hole would be just above the top of the rim and the other just below the bottom of the rim. The catch here is that the holes need to be opposite each other (almost like they would intersect to make an X if they weren't a foot apart) Next, we took 2 ft. long pieces of 3/8" rebar and put one through each hole (1ft. might work, depending on tree and rim size). After welding the rebar to the rims, the tree is locked in place. Since the pieces of rebar are not running the same direction, the tree cannot slide from side to side while inside the rim either. We put them in the pond last weekend, some completely submerged and some about 6" sticking out of the water. It has worked like a charm so far. Like I said, I don't know how that would work on a large scale, but for our small job it worked. With the rims, rebar, and welding, the trees are also not tipping over or moving an inch any time soon. I took some pictures of the process, and I'll try to post a few if anyone would care to see. Hope that helps and have fun with it!
Dave V
