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A corm is the swollen base of a stem axis enclosed by dry scale-like leaves that form a protective tunic.

Photo of an elephant's ear corm.

Elephant's ear (Alocasia)

Illustation of an elephant's ear corm, with the following associated parts identified: remnants of tunic, lateral bud, fleshy roots, node, new developing corm, and flower stem.

A corm is a solid stem structure with distinct nodes and internodes.

In contrast, a bulb's interior is predominantly leaf scales and its stem is the compressed basal plate.

Cross section illustration of a corm, with the following parts identified: old corm, new flowering corm, new corm, roots of old corm, cormels, leaf bases, new bud, and old flowering shoot.

Some species like crocus and gladiolus, produce a corm that is an annual structure (old corm) replaced with a new corm each year.

Cormels form at the base of the new corm and are a natural form of multiplication.

Photo of a crocus plant with the old and new corms identified.

Crocus

Photo of a gladiolus plant, with the old and new corms, and cormel identified.

Gladiolus