Growers have found that planting corms deep and in rows spaced 2–3 cm apart makes more threads, whereas planting depths of 8–10 cm makes more flowers and corms. Saffron crocuses grow best in crumbly, moist and well-drained clay soils with high organic content. They are often planted in raised beds, to help with drainage. Farmers often use 20–30 tonnes of manure per hectare on the plants before plating the corms The buds do not start to grow until early autumn, then in the middle of autumn the plants begin to flower. Picking the flowers must be done quickly: they flower at dawn, but curl up and die during the day. The flowers of the saffron crocuses only last for one or two weeks. From 150 flowers, the farmer can get about 1 g of dry saffron threads. To produce 12 g of dried saffron (72 g freshly harvested) would take about 1 kg of flowers (1 lb for 0.2 oz of dried saffron). It can be worked out from this that one freshly picked flower makes 0.03 g of fresh saffron, or 0.007 g of dried saffron.