I'd like to know if anyone in Louisiana grows flax, too. I want some, but have delayed getting any because I'm not sure if the climate is right.

If anybody has flax here, what kind do you have, and does it do well for you? How tall does it get? Does it need any special treatment? I want to put mine on the back side of my koi pond, if its even practical to have flax here.

Blue flax, (linum lewisii) is a western prairie plant. It prefers well-drained soils, and will thrive in semi-arid conditions.
If you do want to grow it, I would suggest a very dry, well-drained sunny spot. I'm not sure if it would do well near a bog.

Here is a link that might be useful: Desert Gardens

I bought seed for blue flax in very early spring last year at Wal Mart. I started some indoors in flats and they germinated easily, but didn't make it till hot weather. I rather suspect I started them too soon and they didn't get enough light indoors. I am going to try them again this year, but sow them into open ground. A package of seed costs very little, and you can't know till you try...