Several years ago, as something of a lark, I planted a dozen corms of the saffron crocus (Crocus sativus).
Why on earth would I do such a (seemingly foolish) thing? Have I not buried enough money in the ground, never to see it again?
Saffron is usually thought of as a hot-climate plant -- something grown under the Mediterranean sun to perfume paellas in Spain and even more exotic dishes in Turkey and North Africa. But as with so many things usually thought, this is wrong. Saffron is as hardy a little cuss as most of the spring-blooming crocuses, and not difficult to grow if you can provide it with sun and good drainage. Most sources I've seen set the hardiness for saffron crocus to USDA zones 6-8 -- that is, where the minimum winter temps range from -15 to 15 F (-26 to -9.4 C). In terms of U.S. geography, that's approximately from Massachusetts to South Carolina. Most gardeners would interpret this to mean 'pretty much anywhere on the east coast,' provided the sun and drainage, and possibly some winter protection.
If you are not yet convinced, you should know that saffron was widely grown in England from the Middle Ages through the 18th C. In his Herball, John Gerard mentions the Essex town of Saffron Walden, and the whole of Cambridgeshire, as centres of saffron production. Saffron Walden in fact took its name from the growth of the saffron industry there; in the medieval period the town was known as Chipping Walden or, earlier, just Walden. The English saffron industry was largely abandoned by the end of the 18th C with the appearance of both artificial dyes and cheaper imported saffron. Still, even now, saffron is commercially grown in Norfolk and in north-east Wales -- hardly Mediterranean climates.
If you happen to live someplace that really is too cold and wet to grow saffron, the plant will oblige you by growing and flowering in pots. If the spice is the stuff of royalty, the crocus itself has the common touch.
Saffron did originate in the Mediterranean. Crocus sativus does not exist in the wild; it is a triploid form of Crocus cartwrightianus, which grows wild on Crete and was domesticated in the Late Bronze Age by the Minoans. It was valuable as dyestuff and medicine and widely traded around the Mediterranean and into Asia very early.
My saffron crocuses dwell in the central bed of my front yard, where I also grow my lilies. There they get full sun in the winter, dappled sun the rest of the year, and the above-mentioned good drainage.
The corms are best planted in the summer, 5 inches deep and about as far apart. The flowers are sterile, so the crocus spreads only by division, and that not quickly. Once every four years or so, dig up the corms, separate the smaller ones, and plant them on their own. They will bloom in the autumn. Gerard says they begin blooming in September; mine usually bloom in mid October.
Harvesting the spice is easy. You need only collect the 3 brilliant red styles from each flower; the rest of the blossom can be left where it is, and they are pretty things. Collecting the styles is best done in the morning before the heat of the day makes them droop. Bring them inside, spread them out on a tray lined with paper towels or other smooth and absorbent surface, lay another towel over them, and leave them somewhere warm and dry for a few days, and then store in a tightly closed jar away from direct sunlight.
You do not harvest much spice from a dozen corms. In an average year I gather enough to make either a paella or a batch of lussekatter. A more determined home grower might plant 150-200 corms, which would produce enough spice for 10-12 recipes.