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Bulbs

Kinds, Structure, and Function

When we speak of "bulbs" we are often referring to any of several types of structures found in geophytes. A geophyte is a type of herbaceous, perennial flowering plant that forms an underground storage structure. No one is sure when the first geophytes evolved, but they have probably been around almost as long as the oldest flowering plants.

There are several types of these specialized undergound storage organs:

True bulbs: Composed of scales attached to a basal plate; The basal plate is a shortened stem; The scales are the bases of leaves or are modified leaves; Some examples are Lilium (true lilies), tulips, Hippeastrum ("amaryllis"), hyacinth, and Narcissus
Corms: A stout, shortened underground stem; There are no scales or leaves; Uusually an annual structure, rebuilt entirely the following year after the spring growth and flowering are completed.; Some examples are Crocus, Gladiolus
Tubers: A fat underground stem; Bears eyes or buds from which new shoots develop; Often the structure is perennial itself; Some examples are potatoes, tuberous Begonia, Cyclamen
Rhizomes: An enlarged undergound stem; Bears one or more buds from which new growth develops; Some examples are Hemerocallis (daylilies), Convallaria (lily of ther valley), Canna, bearded garden Iris

It seems that bulbs evolved to enable plants to survive seasonally adverse conditions. It may have been that they evolved during the warm Cretaceous Age in seasonally arid climates, where a wet season conducive to growing alternated with a dry season, which could otherwise have killed the plants. Perhaps some of these climates subsequently changed so that there was a cold season, which could otherwise have killed the plants, alternating with a warm season, a time conducive to growing.

Propagation of Bulbs:

Growing bulbs from seeds:

Families of Bulbs:

For information about this account, contact:

James E. Shields, <shieldsgardens@gmail.com>, webmaster

Last revised: 10 February 2012