Niranjana Gopal creator Mini Sankar (Guide) text Vellanikkara Department of Floriculture and Landscape Architecture, College of Agriculture 2021 monographic 77,xiiip. The study entitled “ Standardization of growing medium and growth retardants for compact growth of potted African marigold” was carried out in the Department of Floriculture and Landscape Architecture, College of Agriculture, Vellanikkara during 2020-2021. The objective of the study was standardization of growing medium and growth retardants for regulating growth of potted African marigold for display purpose. The experiment consisted of five different media viz; cocopeat (60%) + vermicompost (20%) + vermiculite (10 %) + rice husk (10%) [M1], cocopeat (60%) + FYM (20%) + vermiculite (10%) + rice husk (10%) [M2], cocopeat (40%) + soil (20%) + vermicompost (20%) + vermiculite (10%) + rice husk(10%) [M3], cocopeat (40%) + soil (20%) + FYM (20%) + vermiculite (10%) + rice husk (10%) [M4] and soil: FYM: sand (1:1:1) [M5] and two growth retardants in three different levels viz; cycocel [750 ppm (GR1), 1000 ppm (GR2) and 1500 ppm (GR3)] and paclobutrazol [30 ppm (GR4), 60 ppm (GR5) and 90 ppm (GR6)] along with a control group of each media without application of growth retardants. Four week old seedling of marigold variety ‘Double Orange’ was used for the study. Observations on vegetative characters, Floral characters as well as the nutrient status of growing media were recorded. With regard to vegetative characters, growing media, growth retardants and interaction between growing media and growth retardants had significant influence. Shortest plants were observed in M1 [cocopeat (60%) + vermicompost (20%) + vermiculite (10 %) + rice husk (10%)] and among the growth retardants, paclobutrazol at 90 ppm [GR6] was found to produce short plants. The same treatment were also found superior with respect to plant spread, number of branches and number of leaves. Regarding interaction effect an improvement in all vegetative parameters was observed in M4 [cocopeat (40%) + soil (20%) +FYM (20%) + vermiculite (10%) + rice husk (10%)] x GR6 [paclobutrazol 90 ppm]. Significant effects of growing media could be observed in floral characters and M4 was found superior with respect to floral characters Viz; number of flowers per plant (10.14), flower diameter (4.61 cm)and field life of individual flowers (9.21 days). M2 was found superior in terms of other floral ABSTRACT characters viz; days taken for first flower bud emergence and days taken from flower bud initiation to flower opening. With respect to the influence of growth retardants on floral characters, a greater number of flowers per plant (9.50), flower diameter (4.22), flowering duration (96 days) and field life of individual flowers were observed by the application of paclobutrazol at 90 ppm. Growing medium and growth retardant interaction had significant influence on floral characters. Lowest days for first flower bud emergence and from flower bud initiation to flower opening were observed in M2 [cocopeat (60%) + FYM (20%) + vermiculite (10%) + rice husk (10%)] x GR1 [cycocel 750 ppm]. Number of flowers per plant was highest in M4 x GR6, M5 x GR6 and M4 x GR5 [paclobutrazol 60 ppm]. Treatment combination M4 x GR6, M5 x GR6 and M4 x GR4 [paclobutrazol 30 ppm] were superior with respect to flower diameter and field life of individual flowers. Analysis of growing media before and after the experiment for differentphysio- chemical properties revealed that M1 had the lowest bulk density (g/cm3 ) highest porosity (%) and water holding capacity (%).The chemical properties pH and EC of all the media were found in the favourable range [pH - 5.8- 6.2; EC<1.5dS/m] both before and after the experiment. Available N, P, K before and after the experiment was found highest in M4 .Plant nutrient content (NPK), Total chlorophyll content and uptake of nitrogen and potassium by plants were also found higher in M4. From the overall performance, it could be noted that the vegetative parameters viz; plant spread, number of branches and number of leaves as well as floral parameters such as number of flowers, size of flowers and field life of individual flowers were in desirable range in treatment combination M4 x GR6. Hence the medium M4 [cocopeat (40%) + soil (20%) + FYM (20%) + vermiculite (10%) + rice husk (10%)] along with application of paclobutrazol 90 ppm [GR6] 20 and 35 days after pinching can be recommended for compact growth of potted Africanmarigold M Sc Commercial flowers Vegetative characters Floral Characters Floriculture and Landscape Architecture 634.1 NIR/ST PG https://krishikosh.egranth.ac.in/handle/1/5810185799 https://krishikosh.egranth.ac.in/handle/1/5810185799