RESUMEN
Background: Hyssop [Hyssopus officinalis L.] is herbaceous perennial plants of Lamiaceae family grown in Europe, the Middle East, Asia, and Northern Africa
Objective: In this research, the effect of harvesting time was studied on essential oil, photosynthetic pigment, and some morphological characteristics of hyssop
Methods: A Field experiment was carried out during 2015/2016 at the Research farm of Payam Noor University of Marand, Iran. The experimental design was laid out as randomized complete block design with three replicates. The three harvesting time [pre-flowering, beginning of flowering and full flowering stages] were arranged in experimental plots
Results: Results indicated that the percentage of essential oil varied for 0.459 to 0.618 in different stage of plant growth. Hyssop essential oil yields increased with time and the highest value of measured traits included plant high, stem diameter, number of secondary and flowering branches, dry weight, chlorophyll [a, b and total], carotenoid, total anthocyanins and total flavonoids was obtained for collected plants in full flowering stage
Conclusion: Overall, the harvesting in full flowering stage was the best time in respect of essential oils content and morphological characteristics in hyssop