effect of the date of planting on morphological characteristics, yield and essential oil content of achillea millefolium sub sp millefolium.l in mashhad climatic conditions

to study the effect of planting date on morphological characteristic, yield and essential oil content of achillea millefolium sub sp millefolium.l., an experiment in a randomized complete blocks design (rcbd) with four treatments including four planting date (6 july, 1 august, 7 september and 7 october) in four replications was conducted. during the growing stage and at the end of experiment period, following factors were measured: time and growth degree day (gdd) to bolting and flowering, plant height, shoot number, lateral inflorescence numbers, inflorescence diameter and height, inflorescence yield, essential oil percentage and yield and total biomass. our results indicated that planting date affects all of the measured factors. in the first planting date, the plants were tall (116 cm) and had big inflorescence (9.97 and 8.72 cm for inflorescence diameter and height respectively). most measured traits (shoot and lateral inflorescence number, inflorescence dry weight and total biomass) had highest value in the august 1st planting date and lowest value in forth planting date (7 october 7th. essential oil percentage was affected by planting date and the highest essential oil percentage (0.17) was produced in 7 october and the lowest (0.13) was obtained in august 1st planting date but the maximum and minimum essential oil yield (1.77 and 0.87 ml) relation with 1 august and 7 september planting date respectively. in conclusion, 1 august is the best date for sowing of the plant. in general, the first of august was the best planting date for this achillea species in mashhad climate.