Abstract In recent years, interest in lavender has been increasing, as it has become not only a subject of agronomic research but also a significant economic factor for various regions, particularly in countries with a Mediterranean climate. To achieve high yields and quality products, it is essential not only to choose the right variety and consider the climatic conditions of the year, but also to implement appropriate sustainable agronomic practices. The present study aims to evaluate how two novel plant growth regulators are affecting the quantitative and qualitative parameters of the lavender variety Yubileyna. The experiment was conducted with a lavender plantation located in the region of the village Tazha (42°38’42.0”N 25°04’49.8” E) over a period of three years (2023-2025). The trial was organised according to the randomised complete block design in three replications and an individual plot size of 25m 2 . Both plant growth regulators, Speed B ® applied in a dose of 3 l ha −1 and Alga900® applied in a dose of 250g ha −1 , were introduced three times in the spring with the start of the active vegetation before the flowering stage at an interval of 10 days. During the trial period, the products have a positive effect on lavender biometric parameters and productivity by an average of 8% (Speed B ®) to 12% for Alga900® compared to the control. Gas chromatographic analysis shows that the product Alga900 improves the quality of the essential oil by helping to synthesise the largest amount of linalyl acetate.
R. Georgieva (2026) studied this question.