Yes, sargassum (the brown seaweed often found on beaches) can be an excellent organic fertilizer and mulch for your garden, but it requires careful preparation. Seaweed is packed with over 60 trace minerals, including potassium, nitrogen, and magnesium, which promote vigorous plant growth and improved root health. However, the primary challenge is its high salt content, which can be toxic to land plants if applied directly. Before using it, you must thoroughly rinse the seaweed with fresh water to remove the salt and any potential microplastics or heavy metals it may have picked up in the ocean. Once rinsed, you can incorporate it into your compost pile—where its high moisture content helps speed up the decomposition of "brown" materials—or use it as a surface mulch to retain moisture and suppress weeds. Over time, the sargassum will break down and release beneficial hormones and nutrients into the soil, acting as a natural growth stimulant that can make fruits sweeter and flowers larger and more vibrant.