Saffron, the crimson stigmas from the Crocus sativus, is the world's most expensive spice. That's because only three of the delicate stigmas are produced by each tiny flower, the hand harvesting required is labor intensive, and more than 14,000 stigmas are needed per ounce of saffron! Yet the aromatic pungency and color the spice lends to dishes is incomparable.
Sally Schneider, author of A New Way to Cook (Artisan, 2001), gives some tips for buying saffron: Purchase whole threads (stigmas) and look for long, unbroken ones; look for bright red color with few yellow threads; and buy in quantity. In Spain it is said that saffron will keep for 20 years.