Although found in the bulb section of most plant retailers come autumn, the saffron crocus actually grows from compressed underground stems known as corms. These specialised stems come complete with dormant buds, each one capable of growing into a genetically identical plant. Each year one new corm will grow on top of the old one, together with some smaller ones which will grow from the base of the plant. These smaller juvenile corms are known as cormels. Their resemblance to a typical bulb is so similar that the difference isn't particularly important until you come to vegetatively propagate from it.
The first technique is the simplest involving the removal of the main stem. This can either be cut or broken away from the main stem or you may wish to try digging it out of the parent corm using the tip of a sharp knife.
The second technique is to cut the parent corm into four equal sections making sure that there is at least one good dormant bud on each section. Dust the cut sides with a fungicidal powder and allow the exposed sections to callous off overnight in a warm dark place such as an airing cupboard. Once again these are now ready to be planted.
Unfortunately propagation by seed isn't an option as this species is a sterile triploid and so does not produce fertile seed. However, if by chance seed is obtained then it is best sown as soon as it is ripe into a cold frame. Click onto How to Grow Crocus from Seed for more information.