High fertilizer costs and environmental impacts are growing concerns in modern agriculture, and the floriculture industry is increasingly adopting the use of biostimulants to enhance plant growth, stress tolerance, and nutrient use efficiency. Despite their potential, the effectiveness and specificity of many biostimulants remain poorly understood. This study evaluated the growth-promoting effects of Lalrise Vita, a commercial biostimulant containing the phosphate solubilizing bacteria Bacillus velezensis. Lalrise Vita's impact on plant growth and health was evaluated using Tagetes patula ‘Durango Yellow’ (French marigolds) and Viola × wittrockiana ‘Clear Yellow’ (pansies). The first experiment evaluated how fertilizer at increasing concentrations affected the plant responses to the biostimulant. A water-soluble fertilizer delivered 50, 150, 300, or 600 mg·L–1 nitrogen (N) from 15N–2.2P–12.5K–2.9Ca–1.2Mg applied once weekly with 100 mL of solution per pot. Lalrise Vita was applied once at transplant at 0.25 g per plant as a substrate drench of 100 mL of solution per pot, with untreated plants as controls for both experiments. The second experiment focused on phosphorus (P) fertilization, with plants receiving increasing P concentrations of 2.5, 5, 10, or 20 mg·L–1 from KH₂PO₄ once a week along with the fertilizer. Plants were fertilized weekly with 100 mL of solution delivering 200 mg·L–1 N from 15N–0P–12.5K–2.9Ca–1.2Mg. Plants were scanned using the Trait Finder (Phenospex), and digital biomass, normalized pigment chlorophyll ratio index, plant senescence reflectance index, and HUE were used to identify differences in plant growth and health. In marigolds, Lalrise Vita improved digital biomass and plant health across all fertilizer rates compared to untreated plants. The greatest differences were observed at lower fertilizer concentrations (50 and 150 mg·L–1 N). Significant improvements were observed in pansies at 50 mg·L–1 N, including increased biomass and improved health indicators. Marigold plants treated with Lalrise Vita at 5 and 10 mg·L–1 P had greater growth, although spectral variables indicated greener foliage at higher P rates in untreated plants. There were no significant differences in pansies between treated and untreated plants, suggesting that Lalrise Vita-treated plants receiving 2.5 mg·L–1 P performed comparably to those receiving 20 mg·L–1 P without Lalrise Vita. Excessive fertilizer (300 and 600 mg·L–1 N) reduced Lalrise Vita’s benefits, as phosphate-solubilizing bacteria are less effective when P is not limiting. However, Lalrise Vita can be used to grow quality crops with reduced fertilizer applications.
