Effects of shading on the morphological development of four varieties of Hemerocallis and negative tolerance evaluation

This study used Hemerocallis ‘EveryDaylily Rose’, ‘Stella De Oro’, ‘Frans Hals’, and H. fulva var. kwanso as test materials, and systematically measured their morphological development and flowering traits under full sunlight and shading gradients of 25%, 50%, and 75%. The results showed that mild shading can promote plant height, leaf length growth, biomass accumulation, or improve flowering quality; However, severe shading leads to a decrease in crown width, reduced flowering volume, and shortened flowering period. Using the membership function method for negative tolerance evaluation, the order of negative tolerance from strong to weak is: Stella De Oro>EveryDaylily Rose>Frans Hals>H. fulva var. kwanso; Stella De Oro perform well under ≤ 50% treatment, while the other three varieties of Hemerocallis had the best traits under 25% treatment. This study provides a theoretical basis for the selection and rational allocation of Hemerocallis varieties in shaded green spaces in northern China.