Categories of bulbs

The plants we loosely call bulbs are in fact divided into four broad categories: true bulbs, corms, tubers/tuberous roots and rhizomes.

A true bulb such as a tulip or daffodil is almost a complete embryo of the plant to come, packed inside a covering of fleshy scales or layers that store the plant’s food

A corm, such as crocus or gladiolus, is a solid mass of storage tissue with a basal plate below and buds, sometimes called eyes, on top.  

A tuber, such as a fancy leafed calladium or calla lily, is also a solid mass of storage tissue with buds but no basal plate. A tuberous rooted plant such as the dahlia, has swollen, food-storing roots; the bud eyes are not on the roots but on the base of the plantís stem.

A rhizome, such as canna, is a thickened underground stem that grows horizontally, with bud eyes on top and roots below.

© Allen. C. Roffey 09:30 19/02/2003