A pound of dry saffron requires NUMBER@1 -- NUMBER@2 flowers , the equivalent of a football field 's area of cultivation -LRB- NUMBER@3 NUMBER@4 flowers or two football fields for a kilogram -RRB- ... Some forty hours of labour are needed to pick NUMBER@5 flowers .

These flowers would need about a football field 's area of cultivation ... Some forty hours of labour are needed to pick NUMBER@5 flowers .
