Modern agriculture faces the challenge of declining soil organic matter, threatening future agricultural productivity. Consequently, alternative methods for enhancing soil stability and improving crop production are necessary. This study investigates the effects of biochar and seaweed extract on the growth, ornamental, and physiological characteristics of Petunia hybrida L. The experiment was conducted using a completely randomized design with four replications. The treatments included a control, barberry biochar at 2% by weight, seaweed extract at 1 ml/L, and a combination of seaweed extract and biochar. Results showed that the highest plant height and stem diameter were observed in plants treated with seaweed extract, showing increases of 24% and 25%, respectively, compared to the control. Flower longevity was significantly influenced, with the longest (6.75 days) and shortest (4.75 days) durations recorded in the seaweed extract and control treatments, respectively. Biochar and seaweed extract also affected the number of days until flowering, with the seaweed extract treatment resulting in the highest (135 days) and biochar treatment the lowest number (117 days). The seaweed extract treatment yielded the highest levels of chlorophyll a, b, total chlorophyll and carotenoids, with increases of 21%, 36%, 25%, and 25%, respectively, over the control. Additionally, the combination treatment of seaweed extract and biochar resulted in the highest levels of phosphorus, potassium, and calcium. The findings demonstrate that biochar and seaweed extract positively influence the growth, ornamental, and physiological traits of Petunia hybrida L., with seaweed extract proving to be more effective than biochar in improving these characteristics.