Effect of planting density on flower and corm yield of Spanish and Iranian Saffron (Crocus sativus L.)

Saffron (Crocus sativus L.), the most expensive spices in the world, is one of the most valuable medicinal plants. The red stigma of this flower is of high value that is called red gold. This plant is sterile due to its triploidy and is reproduced vegetatively by corm. Flowering begins during the fall weather, and is followed by a vegetative stage until spring of the following year. In the next phase, saffron leaves turn yellow and wilt. During the growing season, mother corms are frequently diminished and female corms are formed, the number and size of which affect the reproductive growth and flower production in the following season.

There are various factors affecting the yield of saffron, among which the size of the native corm and selection of appropriate planting density are of utmost importance. Increasing the weight and size of the native corm can lead to the increase of leaf area and saffron dry matter production during the growing season, resulting in more female corms. During planting, large corms can increase flower number, stigma yield, and yields of female corms, compared to smaller corms. Researchers also suggested planting density and proper depth as contributing factors in increasing the efficiency of using available resources to increase saffron yield per unit area. Plant density per unit area depends on the type and method of cultivation, habitats of farmers, and corm size. Studies have shown that the highest saffron yield can be achieved at 50 corm.m -2 . Increasing the planting density of saffron corm from 8 to 21 ton/ha could significantly increase the stigma yield. In this regard, the highest flower and stigma yield was observed at 11-ton density and 15 cm planting depth. The obtained results of investigating different planting patterns (row, random, and clump) and different corm densities indicated that the highest yield of saffron flowers was obtained in row crop treatment with 12 tons of corms per hectare. With this background in mind, a study addressing the effect of planting density on flower and corm yield of Spanish and Iranian saffron (Crocus sativus L.) types was conducted on the Research Farm of the Faculty of Agriculture, Ferdowsi University of Mashhad. The findings suggested that the highest number of flowers and yields were observed at 48 and 60 corm.m -2 , respectively. With regard to the corm type, flower production was significantly higher in Iranian corms, while Spanish corms reinforced replacement corms. It should be noted that flower production in the first year depends on the size of the cultivated corms. Additionally, nutrition management can be effective in saffron flower indices in the following years.