I agree with you Leon. Some irises just will not thrive for me while others increase and bloom against all odds. I am on my second try with Midnight Oil and it has just been sulking since I planted it. If it does not grow this time I am going to admire it from afar. Some years rainfall, or the lack thereof, makes a big difference in my irises and with all the rain this spring it is a good indicator of which ones are hardiest in my area. I think my medians can tolerate more water than the TB's can.
