Nowadays, growing medicinal plants in sustainable agricultural systems in which sustainable plant nutrition strategies play an important role are more focused. Seeds of milk thistle plants (Silybum marianum [L.] Gaertn.) are the main source of silymarin which is known as the biological active component helpful in treating liver and biliary diseases and also preventing liver cancer. Phenological stages, especially the reproduction time and maturity of milk thistle, might be affected by management strategies. In order to investigate the potential effects of different nourishment systems on phenological stages of milk thistle, a field experiment was conducted during 2010–2011, at Research Station, Faculty of Agriculture, Ferdowsi University of Mashhad, Iran. Twelve nutrition systems comprising single and integrated nutrition systems of vermicompost, poultry manure, chemical fertilizer, mycorrhiza (Glomus mosseae), and bio-sulfur (Thiobacillus sp.) were compared in a completely randomized block design with three replications. According to the results, growth development stages of milk thistle in Mashhad climate were found to have four discrete stages; vegetative, elongating, flowering, and seed maturation stage. Analysis of variance of heat units, expressed in growing degree-days (GDDs), showed that elongating and flowering stages were significantly affected by different nutrition systems (P < 0.05). Milk thistle plants treated with mycorrhiza started the elongating stage and flowering stage with less GDDs (845 and 1001 °C, respectively) compared with other treatments. The highest amount of GDDs for starting the elongating stage was recorded for chemical fertilizer treatment and plants under integrated use of mycorrhiza and vermicompost required more GDDs to start flowering stage.

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