Daylilies can also suffer from summer dormancy. I have had two daylily cultivars (out of several hundred) that sprouted normally in the spring, grew normally, produced scapes and while the scapes were developing all the leaves died back. The end result was a scape all by itself blooming. But in other years, when I have mulched the plants they did not go summer dormant. One of the daylilies that went summer dormant did return as smaller fans. The other one returned normally with fans that grew to their original size (which however was not very large).
Arisumi found that daylilies do not grow well at constant high temperatures. He wrote "At 85° and 95° the plants grew rapidly during the first 3 to 4 weeks and then became progressively chlorotic and the older leaves dried prematurely."
