Saffron is a spice derived from the flower of Crocus sativus, commonly known as the "saffron crocus". The vivid crimson stigma and styles, called threads, are collected and dried for use mainly as a seasoning and colouring agent in food.Saffron has long been the world's most costly spice by weight. Saffron is a spice made from the stigmas of the fall-flowering plant Crocus sativus, a member of the iris family.Saffron threads are fine and have a yellow tendril on one end and a flute on the other. Ground saffron is red to red-orange in color. Saffron is suitable for vegan, gluten-free, and paleo diets.