Plant growth is limited by salinity stress. There are few strategies for alleviating it although Arthrospira platensis and silicon can stimulate plants to grow under stress conditions. The aim of this work was to study the effects of both a single and a joint application of Arthrospira platensis and silicon on the growth of Pelargonium hortorum L.H. Bailey under salt stress conditions. Plants were exposed to 2.0, 3.0, and 3.5 dS m−1 EC (electrical conductivity), with and without the application

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... of microalgae and silicon. At the end of the trial, the biometric parameters and the plant analysis were determined. The microalgae hydrolysate concentration was 5 g L−1 and the silicon concentration was 150 mg L−1. Foliar spraying was applied weekly. Pelargonium can be grown in moderately saline irrigation water (3.0 dS m−1). This bedding plant mitigates salt stress by avoiding the uptake of Cl− ions and by tolerating a high Na+ concentration in the tissue. The joint foliar application of Arthrospira microalgae and silicon stimulates root, shoot, leaf, and flower formation in the Pelargonium hortorum L.H. Bailey crop under salinity conditions (3.5 dS m−1).