Rule of thumb in my zone is not to fertilize until mid February or six weeks before anticipated bloom. I usually give my irises love (fertilizer) on Valentine's Day if it is not icy. Theory being if I fed them now new growth would get frozen and they would expend a lot of energy on false starts. I am interested to see the results of your tests Gabe. Also it would help if you kept dates of hard freezes and seeing new growth starts. This old dog CAN learn new tricks. smiles
