In order to investigate the effect of planting time and density of Achilleamillefolium under field condition, this project was performed atForest and Rangelands Research Institute, Karaj, Iran in 2011. The experiment was conducted as split plot in the form of a randomized complete block design with three replications. The main factor was four planting times(6 March, 26 March, 14 April and 5 May) and the sub factor was three density included100 plants per square meter (10*10cm), 25 plants per square meter (20*20cm) and 11 plants per square meter (30*30cm). The analysis of variance showed that the effect of planting time, density and their interaction significantly affected the plant fresh weight, root length, root width, inflorescenceheight, stem height, sub stem number, canopy diameter, the amount of chlorophyll a, chlorophyll b and total chlorophyll.The highest plant fresh weight (161.23g), inflorescenceheight (4.75cm) and stem height (57.77cm) was observed in the second planting time (25 March).The first planting time (6 March) had the highest root length, sub stem number and canopy diameter with 21.22cm, 14.88n/p and 25.11cm, respectively. The highest number of sub stem (14.83n/p) and canopy diameter (22.58cm) belonged to planting spaces 30*30cm. The highest plant weight, root length, inflorescence and stem height was observed in planting spaces of 20*20cm with 139.33g, 20cm, 4.06cm and 54.75cm. The results indicated that among the four planting times, the first and second planting time provide more opportunities for plant growth anddensity of 30*30cmprovidessufficient spacefor plant growth.
