Algae magic for tomatoes – strong roots, vigorous growth

Every week, we share fascinating insights from the world of science, explained in simple terms and accompanied by tips for your garden or houseplants. We’re kicking things off with a favourite among many amateur gardeners: the tomato.

Tomatoes, like other vegetables, hardly contain the same levels of nutrients as they used to. This is mainly because the soil in which they grow is now depleted of nutrients.

What are biostimulants?

Biostimulants are natural aids that do not directly fertilise plants, but instead make them stronger, healthier and more resilient to stress. They support the roots, improve nutrient uptake and help the plant cope better with drought or heat. Microalgae – such as spirulina or chlorella – are particularly interesting because they contain valuable substances such as polysaccharides, amino acids and plant hormones.

du Jardin, P. (2015). Plant biostimulants: Definition, concept, main categories and regulation. Scientia Horticulturae, 196, 3–14. DOI: 10.1016/j.scienta.2015.09.021

Kumar, A., et al. (2022). Microalgal-based biostimulants as alleviators of biotic and abiotic stresses in crop plants. In: Microbial Biostimulants for Sustainable Agriculture. Springer. DOI: 10.1007/978-981-16-6335-2_5

Why are tomatoes grown with algae stronger?

Scientists have discovered that polysaccharides from the microalga Spirulina platensis cause tomato plants to grow 20% larger. Even more impressive: the roots became 230% heavier – meaning they were much stronger. This allows the plants to absorb more water and nutrients and remain healthier.

El-Arroussi, H., et al. (2016). Microalgae polysaccharides, a promising plant growth biostimulant. J. Algal Biomass Utilization, 7(