A biostimulant is a substance or microorganism applied to plants or growing media to influence plant processes independently of supplying significant amounts of nutrients. Biostimulants are used to support root development, nutrient uptake, stress tolerance, growth efficiency, or microbial activity in the root zone.
Common biostimulants include seaweed extracts, humic substances, amino acid products, beneficial bacteria, mycorrhizal fungi, protein hydrolysates, and some fermentation-based additives. Unlike fertilizers, which primarily provide essential nutrients such as nitrogen, phosphorus, and potassium, biostimulants are valued for their indirect effects on plant growth and physiology.
In indoor and outdoor gardening, biostimulants are often used during transplanting, recovery from stress, or periods of active growth. Their effectiveness varies with plant species, environmental conditions, substrate composition, and overall plant health. Many products combine biostimulant ingredients with fertilizers or micronutrients, which can blur the distinction between categories.
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