Two field experiments were conducted in the farm of the Department of Agricultural Botany, Faculty of Agriculture, Al-Azhar University, Assiut, Egypt. during the two winter seasons 2021/2022 and 2022/2023, in order to study the effect of some growth stimulants such as yeast extract (5, 10, 15 g/l), humic acid (0.5, 1, 1.5 g/l) and algae extract (4, 6, 8 cm3/l) on some morphological, physiological and floral characteristics of two cultivars of calendula officinalis plant double flower and single flower compared to control (tap water). The results showed that the double flower cultivar was significantly superior in morphological characteristics (plant height, number of branches / plants, stem diameter, number of leaves, leaf area (cm2) plant-1, fresh weight and dry weight) except for the characteristics of plant height in the first season and the number of branches in the second season where the opposite happened. Single flower cultivar also caused significant superiority in the physiological characteristics, namely (chlorophyll a, chlorophyll b, total chlorophyll, total carotenoid in the leaves) except for total carotenoid in flowers for both seasons. As for the floral characteristics, which are (diameter of inflorescence, number of rays (flowers) / inflorescence, fresh and dry weight of the inflorescences / plant), the double flower cultivar recorded the highest results compared to the single flower cultivar except for number of inflorescences / plant where the opposite happened. The results also recorded that foliar spraying of yeast extract at (5, 10 and 15 g/l), humic acid at (0.5, 1, 1.5 g/l) and algae extract at (4 cm3/L) improved the morphological, physiological and floral characteristics of both cultivars of calendula officinalis during the two study seasons compared to control (tap water). On the contrary, spraying with algae extract at (6, 8 cm/l) caused a noticeable decrease in the morphological, physiological and floral characteristics mentioned above for both cultivars of calendula officinalis during the two seasons of the study compared to control (tap water).  Finally, the study showed that the use of yeast extract at a concentration of 10 g/l followed by humic acid at a concentration of 1 g/l as growth biostimulants sprayed on the calendula officinalis plant has caused a significant improvement in morphological, physiological and floral characteristics, especially with the double flower cultivar, and this is confirmed by the results under the same study conditions.