Iris go dormant in the heat, so now is probably perfect if you can stand to do it.
Do you really mean the were planted in 2008? So have only bloomed once since then? Iris do have to be divided often, 3-5 years depending on how fast they have muliplied, but doesn't seem like they should be at that stage yet.

Thanks for responding. When transplanted in 2008, they had blooms at that time, but did not bloom in 2009. Someone told me that they do not bloom for 2 years after transplanting and that is what happened--and they were beautiful blooms too. They are kinda crowded, now that I look at them, so I guess there'll be some diggin' in my near future.

If you are going to get a soil test, then I would wait until I got the results back, to see what I needed to do for the soil before I replant. I mean, that is what the soil test is for after all. I see any rejuvenation project as an opportunity to add add in organic material, and whatever nutrients are needed, only in the quantities needed and no more than that.

are they in absolute full sun???

of the 20 i added last spring.. half bloomed.. half didnt.. that is not uncommon for transplants of smaller pieces ....

check the link .. now is the perfect time for lifting.. moving.. dividing ... note that none of those pictured is in any shade ... fan the leaves if you do so ...

ken

Here is a link that might be useful: link

Asking about sun is a good question. Where these iris are planted is a good thing to consider if your iris aren't blooming well. And I also have bought some iris that were not very large rhizomes, and they didn't bloom the following year, but took more than a year to get big enough to bloom. I don't know about Oklahoma, I usually do mine in August, but I bet this is an okay time to divide your iris. Wear a hat and soak your shirt.