Phonological stages and formation of replacement corms of saffron (Crocus sativus L.) during growing period

Saffron (Crocus sativus L.) is a perennial and triploid- geophyte crop which can be maintained up to 8–10 years. During each season, saffron propagates exclusively by replacement corms produced from the mother corm after blooming. The new corms are formed above the old ones, so the crop density increases more and more. Therefore, the flower number and dry stigma yield of saffron are relatively low in the first year and increases to maximum in the fifth to sixth year after planting. The stigma yield of saffron largely depends on weather and soil conditions during replacement corms formation. Research activities have been conducted to developing the appropriate and new agronomic technologies can result in economic levels of production and improve the crop yield. The objective of this review article is to describe and discuss the phonological stages of saffron based on mother- replacement corms behaviors. In addition, relevant literature related to main factors affected the replacement corms behavior is reviewed.