This study investigates the growth and floral performance of three Lilium cultivars (Lilium candidum, Lilium martagon, and Lilium lancifolium) under four irrigation regimes corresponding to 60%, 80%, 100%, and 120% of crop evapotranspiration, using treated wastewater as the irrigation source. The experiment, conducted under controlled greenhouse conditions, assesses various vegetative and floral traits, including flower number, flower diameter, stem diameter, flower stalk length, fresh weight, and stem length. The results reveal that cultivar identity significantly influences all evaluated parameters, while irrigation levels have a marked effect on stem diameter, flower stalk length, fresh biomass, and stem length. Differential responses to irrigation treatments are observed among cultivars, indicating species-specific sensitivity to water availability. Overall, higher irrigation levels tend to enhance both vegetative growth and floral attributes; however, notable variations in water use efficiency are detected among the cultivars. These findings underscore the importance of appropriate cultivar selection and precise irrigation management to improve production quality and promote sustainable water use in horticultural practices.