The cultivated saffron (saffron crocus "C. sativus") flowers in the autumn and comes up every year, so it is known as a perennial plant. It does not grow wild, and is now a triploid form of the eastern Mediterranean plant called "Crocus cartwrightianus". It is thought that "C. cartwrightianus" came from Crete. The saffron crocus resulted when "C. cartwrightianus" was subjected to a lot of artificial selection by growers who wanted plants with longer stigmas. It can not reproduce because the saffron crocus's purple flowers do not produce useful seeds. This means that reproduction needs human help. The corms (underground bulb-like starch-storing organs) must be dug up, broken apart, and planted again. A corm lives for only one season, reproducing by splitting into up to ten "cormlets" that will grow into new plants. The corms are small brown balls up to in diameter and are covered in thick parallel fibres.