Seaweed extract is a concentrated plant supplement made by processing marine algae, commonly brown seaweeds such as kelp. It is used in gardening to supply trace minerals, organic compounds, and biologically active substances that may support root growth, stress tolerance, and overall plant vigor.
Unlike complete fertilizers, seaweed extracts usually contain low amounts of nitrogen, phosphorus, and potassium. Their primary role is as a biostimulant rather than a major nutrient source. Many products contain naturally occurring compounds such as cytokinins, auxins, amino acids, and carbohydrates, along with micronutrients derived from the seaweed itself.
Seaweed extracts are commonly applied as liquid drenches, foliar sprays, or additives to irrigation systems. In container growing, they are often used after transplanting, during periods of environmental stress, or alongside regular fertilization programs. Product strength and composition vary depending on the seaweed species, extraction process, and formulation.
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