I learned the hard way that all I needed to add to my sand (called soil) is mushroom compose. No more black cow, sphagnum moss, etc. All plants, potted or in-ground get 2/3 sand 1/3 mushroom compose. Mush. Comp. added couple times during the season too. That's what they'll have when transplanted into the ground.
So my question is can you start Irises off in pots and transplant later? What is later? Before a cold snap or before spring? While I'm on a roll, do irises require a dormant period?
Do irises require any of the "special" fertilizers? One was 5-50-10 which just blew me away. I ASSUME a force bloomer ????
Having my Irises thrive in Florida is my main concern.
One more thing. Sun. When everyone else says sun for at least six hours, my hardiest plants are wilting. Where I intend to put my Irises will have sun from rise till 4-5 p.m. If it didn't rain that day, I have to water. By day two, plants are in rough shape, and day three their dead.
I think that irises can be difficult in FL. The low nitrogen fertilizer is a good idea. Otherwise it will be all leaves. Look for http://www.irises.org for the American Iris Society. Follow 'links' for Florida. Someone there could tell you more about working in your climate.
I tried TB irises in Cocoa Beach and had bloom only once. The first season after bringing from NY. I have since moved on to Walking iris, yellow and white, and the large bloom white (African) irises that I bought at Rockledge Gardens. The winters just aren't cold enough, long enough. Good luck with your experiments.