Munson noted three conditions that affect daylilies in the summer in his book.
In one they die and rot away if they are divided in August or September in the South and replanted when there is high heat, humidity, rain and a rich soil.
In another their leaves simply start to yellow even when the clump has been undisturbed and then they die and rot away.
In a third the leaves yellow and then start to die back; the plant will eventually recover but it will not bloom that year (presumably because it is smaller).
