Effect of fertiliser application method and nutrient solution pH on growth, yield and flower quality of gardenia ( <i>Gardenia jasminoides</i> )

ABSTRACT Gardenia jasminoides , a popular ornamental species, often shows reduced growth and flowering due to poor nutrient management. This two‐year study aimed to assess the effect of fertiliser application method and nutrient solution acidity on the performance of gardenia. Two application methods (foliar/soil drench) and four pH levels (5, 6, 7, and 8) were tested to evaluate their effects on plant growth, leaf physiology, and flower yield and quality. Soil drenching significantly improved shoot growth traits along with leaf nitrogen, phosphorus, and calcium concentrations and flower yield compared to foliar spray. Adjusting the nutrient solution to pH 6 notably enhanced shoot biomass and flower traits relative to pH 5 and 8. Nutrient drenching at pH 6 led to a 90% increase in chlorophyll content, 200% in leaf area, 84% in leaf fresh weight, and 155% in flower number, among other improvements, compared to foliar spraying at the same pH. However, it also caused reductions in root fresh weight (−42%), leaf iron (−47%), and soil respiration (−15%). These findings indicate that soil drenching at pH 6 optimises gardenia growth and flower yield. Further research is recommended to explore long‐term nutrient uptake and translocation mechanisms under different fertilisation strategies at optimal pH.