Allelopathy is one of the main factors limiting the plants growth. The present study investigated the effect of aqueous extract of leaves and fruit of Artemisia sieberi that is an important species for rangeland rehabilitation on seed germination and seedling growth of three alfalfa species (Medicago sativa cv. Nikshahri,‌ Medicago polymorpha and Medicago scutellata cv. Robinson) in laboratory and glasshouse. Treatments were five concentrations of 0, 25, 50, 75 100% Artemisia extract. Treatments were evaluated using a completely randomized factorial experiment in four replications in germinator and pots separately (2014). Data were collected and analyzed for the germination percent, germination rate, seedling length, seedling weight and seed vigor index. Means comparisons were made using Duncan test. The results showed significant differences between extract concentrations of Artemisia on all of traits in both growth conditions (P<0.05). There was a decrease trend for all of the traits. Germination percent of M. polymorpha was stopped in low concentration of Artemisia extracts (25%) whereas there were linear decreasing trends for the other specie until irrigation by 100% extraction. M. sativa had a higher germination rate and M. scutellata had higher vigor index values in all the treatments. Results of the study indicated that Artemisia had strong allelopathic effects and prevents from the germination and seedling growth of alfalfa. تفاصيل المقالة