LA tend to be taller, have wider foliage which is a more yellow green color, and have long rhizomes which tend to walk some distance with time...

Sibs have narrow blue-green foliage, small rhizomes and are clump forming.

Thank you, Chadinlg!

I can't really tell all of them apart yet either, but this is what I look for:
Siberians tend to be blues and purples, though that is changing. They have a pretty little stained-glass like pattern on their falls right in the throat in most cases.

Louisianas come in yellows, whites, reds, pinks and oranges more often. They have a "signal" in their throats in many cases.

What about soil/moisture requirements for both - same?

Both would prefer moist soil when growing, tending on the acid side. LA's can be grown in a swamp, but do not require it. I don't think Sibs would like to drown ...

Thanks a lot!

I have a number of Siberian Iris, two Japanese Iris and one Louisiana Iris. They grow great here in our acid loam which stays pretty moist. One difference that I noticed is that the LI is still green while all the SIBs are dry and brown.

Some of the newer SIB hybrids I have are yellow, red (sort of), purple, light blue as well as deeper blue. And combinations of these colors.

My Louisiana Iris is "Dorothea K. Williams". It has not bloomed yet, but is supposed to be blue violet.

Natalie, I'm chiming in late, but as far south as you are, you'll likely have better luck with Louisianas than Siberians. Siberians like to get COLD in the winter, and might not do well for you as a result of too little cold. That said, I know folks that grew Siberians perfectly well in zone 7a (central Virginia), but they did mention that not all varieties were happy for them. So you might want to check with local iris societies and see if anyone near you is successfully growing them, and if so, which ones. Louisianas, on the other hand, love heat and humidity! Good luck!

There is one growing in my garden that fits Louisiana Iris description. I always want to grow something that is a challenge in my zone :). Would love to give Siberian a chance.
Thank you all for your responses.
Happy gardening!
Natalie

A little bit of shade, and some extra water, and sibs will grow great for you, Natalie.