Iris fertilizer or soil amendments
Hi, Well iris plants grow from fleshy surface roots called rhizomes. So, it's not unusual to see the rhizomes above soil level. Because your iris are older I don't think fertilizer will help much. I think they are probably too crowded and require division. Iris require division every few years to keep them happy and vigorous. Wait until late summer and dig up the clump. Then, with sharp knife or spade, cut away each section, making sure each section has at least one fan of foliage. Then, replant, spacing them at least a foot apart.
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