Effect of biostimulants on growth and flowering of Tagetes erecta L.

Tagetes erecta L., commonly known as marigold, has been recognised for its diverse medicinal properties, which have been increasingly studied in recent years. The use of biostimulants (BSs) in marigold production is vital for enhancing growth, improving flowering and increasing floral yield. This study was designed to examine the effect of BSs on the growth, yield and flowering parameters of African marigold F1 ‘Antigua Orange’ (T. erecta L.). Plants were sprayed three times during the growing period after 30 days, 40 days and 50 days from transplanting with control (tap water), Spirulina (0.1 g · L⁻¹), Moringa leaves extract (MLE) (3%), chitosan (0.1 g · L⁻¹) and pollen grains date palm extract (PGPE) (0.1 g · L⁻¹). Results revealed that the plants sprayed with all the BS treatments significantly increased all growth, flowering and yield attributes compared with the non-treated plants. Chitosan and MLE had the maximum growth attributes, flower quality parameters, flower behaviour and flower yield per plant and per hectare. Spirulina treatment improved the flowering rate by 86.67%. In comparison, MLE recorded a maximum increase of flower yield per plant and per ha as 66.49%, followed by PGPE by 63.17% over the control. PGPE was more effective in promoting root elongation by 51.27%. The findings contribute to sustainable agriculture and horticulture by providing eco-friendly strategies to enhance marigold production, leading to improved crop management practices, reduced reliance on synthetic fertilisers and increased economic returns for growers.