I assume you are talking about a TB.? Several years ago I went on a quest for a black iris. I have been really un-impressed with the results. In my yard they are all very dark purple, red, plum or blue. So I tried to find one that is the darkest. I still grow Anvil of Darkness, Before The Storm, Old Black Magic and Coal Seams. I recently shared away Men In Black. It was interesting as it had a bronze beard but in my garden I just do not have the space to grow that many 'black' irises. I had several people tell me that Midnight Oil was the darkest they grew. I tried a rhizome of it twice and it just disappeared so I said a fond farewell to that idea. If you want a smaller iris Dark Matter is a very black looking SDB with ruffles and Black Lightening is a very dark blue one. I grow a little BB, Honky Tonk Hussy, that is so dark red it is hard to capture any color in a photo of it. Keep records of your progress in selecting a 'black iris' as others will come along with the same questions I had.