I searched and searched for any scientific information, or even old wives tales for information about summer dormancy, heat dormancy, and even drought dormancy in daylilies.
There is very little information I can find on the subject. But, I have often been told that daylilies are monocots similar to corn, so I thought to look for information about heat stress on corn (many more dollars put into research on commercial food crops than will ever be spent on research for daylilies).
This was one of the best articles I found (easy to understand) and I thought highly informative and gave what I thought was a pretty good explanation of the causes of heat dormancy in corn and soybeans, and hopefully most of this information can also be applied to daylilies.
https://cropwatch.unl.edu/2016...
The most important part to me is listed under:
IS THERE ANYTHING THAT CAN BE DONE TO MITIGATE EXTREME HEAT STRESS ON PLANTS? Then lists nine things that could be done for corn and soybeans, they may not all apply to daylilies but the general principals I feel would.
Basically, it just says that small amounts of shallow watering can be a benefit, and will not necessarily cause the roots to be shallow or not continue to grow deeper due to other reasons. I think we have all read that it is better to water daylilies deeply so the roots will grow deeper. It also states that soil fertility can impact the degree to which heat stress can affect plants (plant stomatal conductance and the transpiration rate were observed to be lower). The article mentions the advantage of having additional residue on the soil surface as a result of reduced and no-till growing methods, which I understand as being mulch in the case of daylilies. The mulch helps reduce the soil temperature and thus is beneficial for root growth and water and nutrient uptake. Also the study suggest that adding micronutrients because they also modified stomatal function and activated physiological and metabolic processes that helped with tissue water potential and heat stress tolerance.
