So.
NEVER ADJUST THE TREE WHEN THERE ARE BOTTLES INSTALLED!
I was installing a new one for my wife, and thought I'd stomp it down just a little bit firmer in the ground...the bottles bounced on the metal posts, and I found myself in a shower of broken glass.
Since it was cold and I was wearing heavy clothing, no damage was done, but it really got my attention!

Today's project is one that several people have asked me about: a bottle tree.
This is a custom in the South, whether it's a welded piece of fantasy or just bottles stuck on the branches of a dead tree.
Materials for this one (what I had on hand on a day too snowy to shop for more steel): 6.5 feet of 5/8 rebar, and about thirty two feet of 3/8 rebar, plus a wicked sharpened cleat that you can step on to drive it into the ground, this makes for a steadier base.
Installed height will be 8 feet, with room for 24 colored bottles.