Enoki mushroom (Flammulina filiformis) waste was converted into biochar that improved water retention, organic matter, and microbial activity in nutrient-poor coastal sand. When combined with Bacillus megaterium, the treatment helped beach morning glory (Ipomoea pes-caprae) grow more successfully in harsh shoreline conditions where plants often struggle to survive. This creates a practical reuse pathway for mushroom-farm waste while helping stabilize vulnerable coastlines and degraded sandy soils.