Thin coated wire works well. Also what I have been using lately is the thin wire hangers you use for suspended ceilings to support the t-bar - it does not rust.
I prefer to have them oriented on an angle as they would grow in nature and as Bud said, it helps prevent crown rot. A rock in the bottom of the pot also help prevent tip overs.
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DaveW
"Every time you spend money, you're casting a vote for the kind of world you want." ~Anna Lappe