It is difficult to give daylilies too much light indoors; too high a temperature is a different matter. Light fixtures that produce more light also tend to run hotter. Temperatures between 65F and 75F are good.
I am using six led tubes each four feet long and each producing 6000 lumens (total 36,000 lumens) over an area that measures 3 by 4 feet with mature daylily plants rather than seedlings. As a guideline both 'Stella de Oro' and 'Happy Returns' have three to four bloom cycles in seven months under those lights. Others such as 'Ming Porcelain', 'Ida's Magic', 'Court Magician', 'Angel's Smile', 'Mississippi Bill Robinson', 'Crystal Blue Persuasion', etc. only have one bloom cycle during the same period.
