What are the main things to look for when differentiating these two? There are conflicting opinions on a plant over on the Hardy Palm and Subtropical Board (http://members3.boardhost.com/HardyPalm/msg/1234753121.html). Any good IDs?

Looks a dead cert like Japonica to me Complete lack of complex branches and hence lack of foliage and without the variable leaves of gigantea ...

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Bamboo...Please note... This plant is seriously addictive and you may lose interest in other, less rewarding plants!

Ps. japonica (AKA: Japanese Arrow) is pretty easy to ID... except when you are trying to differentiate between it and some of the other Ps. types. Looks like a Pseudosasa to me. It grows like a weed here. Arundinaria boos have lots of branches per node. Of course, Arundinaria is the genus that originally had all the non-Phyllostachys boos in it, and I have to wonder if there really are that many boos that really belong to or in that genus (other than gigantea).

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Happy trails...

I agree. As far as I know, real Arundinarias are Appalachiana and Gigantea.
I read on a site that Funghomii wasn't really an Arundinaria and some info on it, and it's naming. I would post the link but I'm on my phone so I can't copy it.
I will edit it in when I get to a computer.

...but for now, I'm going to bed. 2 AM is WAY too late. Waking up should be pleasant tomorrow...


And as for the ID of the plant in the pictures, I am, like MarkJ, pretty certain it is Ps. Japonica, but there is also A TON of Arundinaria In that area. I live pretty close to the Chattahoochee.