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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
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
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
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, <>, webmaster

Last revised: 10 February 2012

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