This research aimed to determine the effects of different levels of marine seaweed extract on growth and yield traits of Roselle (Hibiscus sabdariffa L.) cultivars (eggplant, red, white, and striped) and their six half diallel hybrids. The experiment layout was in a randomized complete block design with a factorial arrangement and three replications. The first factor included four cultivars and their semi-reciprocal hybrids, while the second factor comprised the foliar application of marine seaweed extract with three concentrations (0, 10, and 20 ml L^-1). The results showed the roselle cultivar eggplant surpassed all other cultivars and provided the highest values for the traits, i.e., plant height, leaf area, dry weight of nuts, nuts per plant, and seeds of nut (160.03 cm, 635.50 cm², 402.77 g plant^-1, 172.44 nuts plant^-1, and 28.69 seeds nut^-1, respectively). The marine seaweed extract with the strongest concentration (20 ml L^-1) also displayed better performance for the above traits (176.02 cm, 615.58 cm², 361.22 g plant^-1, 176.74 nuts plant^-1, and 25.80 seeds nut^-1, respectively).

Keywords: Roselle (H. sabdariffa L.), cultivars, seaweed extract, growth and yield traits

Key findings: The Roselle (H. sabdariffa L.) cultivar eggplant excelled all other cultivars for growth and yield traits. The marine seaweed with the strongest concentration (20 ml L^-1) also provided better performance for growth and yield traits in Roselle.