What Is a Crocus Bulb?

The Purpose of a Corm

• A corm is a modified storage swelling at the base of the stem, according to the University of Illinois. It stores all the energy and nutrients the plant needs to survive. Crocuses build up energy during the growing season, either spring or fall, and go dormant during the winter. The energy stored in the corm will help the plant sprout and bloom during the next growing season. Some bulbs are too tender to be left in the ground during a cold winter, but crocus corms thrive equally well during cold or warm winters.

The Structure of a Corm

• At the bottom of a corm is a flat, circular structure called a basal plate. Roots sprout from the basal plate at the beginning of the growing season. Above the basal plate is the bulbous corm where the nutrients are stored. The corm comes to a point at its tip, and this is the growing point. The flower stems and leaves sprout from the growing point.

Propagation

• Some varieties of crocuses produce seeds, so cormels usually are the most reliable method of propagation. Cormels are pea-size offshoots of corms. They can be found attached to the corm just above the basal plate. To retrieve them, carefully dig up the corm at the end of the growing season and gently pull off the cormels. According to the University of Illinois, cormels can be planted in an out-of-the-way spot until they mature to flowering size. Once the cormels are gone, the corm can be replanted.

Varieties of Crocus

• Two main types of crocus exist: spring flowering and fall flowering. Between them there are about 50 species cultivated for gardens. Crocus vernas, also called Dutch crocus, is among the spring flowering species. These crocuses bloom in early spring with blossoms in white, yellow or purple. Crocus sativas is a fall blooming species with blooms of white or purple. The cooking spice, saffron, is harvested from the stamens of the Crocus sativas.