corms

Corms are a type of underground storage organ formed from a swollen, vertical stem. They store nutrients and enable perennial plants to survive adverse seasons. At the top of a corm a growth point produces shoots, while roots emerge from the basal plate at the bottom. Unlike bulbs, which are composed of concentric layers of scale leaves surrounding a rudimentary shoot, corms are generally solid and may be protected by a papery tunic. Some corms are tunicate (with a dry outer covering), others are tunicless.

Geophytes with corms leaf out seasonally; during adverse conditions plants die back to the corm, and new shoots emerge when conditions improve. Reproduction is chiefly vegetative: new corms or cormels form from the base of the old corm, enabling propagation without seeds.

Examples include Gladiolus, Crocosmia, Freesia, and Crocus, the latter including the saffron crocus. Corms are widely cultivated as ornamental plants for spring and summer displays. They are also studied for their physiological adaptations to storage and recovery.

Care notes: well-drained soil is important; corms can be lifted and stored dry in cold climates; rotting and pests can affect them.