There is a lot of information out there on how to grow saffron so I'm going to share what I've done. I ordered and bought 10 corms in October which arrived last week. There are a several places in New Zealand that sell corms; terraza saffron, Mapua country trading, or trade me. The corms need to be ordered in August/ October and sell out quickly so it pays to keep in touch with these companies.
Being a crocus, Saffron flowers in autumn and are dormant in spring/ summer. Late summer is the best time to plant your corms. It pays to keep the corms relatively dry in summer (if in a container the corms can be moved into a dry spot) but water every second day when it is flowering. Plant in full sun but they can have some shade as well as long as they get plenty of sunlight the rest of the day.
Once the corms arrive (late summer/ early autumn) it is recommended to put them in the ground straight away or if you can't plant them straight away keep them in a dry, warm and dark place till you can plant them.
Saffron needs to be grown in very free draining soil otherwise they will rot. Clay soils (which is what I have) is the worst type of soil to grow saffron in, so I decided to plant my corms in a laundry tub to hopefully give them maximum chance of growing and producing a good yield. I even splashed out and bought top quality potting mix (normally I buy the cheapest one). I filled the bottom 10cm or so with quarry sand (not beach sand; it's too salty) to help increase the drainage in the tub. I also figured the metal will keep the corms warmer in autumn/ winter as well. I planted the corms 10 cms deep and 10 cms apart. I then filled the holes with compost to add some extra nutrients to the soil. After I planted the corms I gave the ground a good soaking with water. Mr Ecochick made me a new spoon label for the saffron. So now I'll just have to wait.