Bulbs - Tapa dura

Mention the word bulb to most people and a whole range of plants comes to mind, including dahlias, gladiolus, irises, lilies, tulips, crocuses, and many others commonly known by this term. But are they "true" bulbs? And just what is a true bulb?

A true bulb is composed of leaves modified for storage and attached to a basal plate that can be considered a squashed stem. Crocuses are regarded as bulbs; in fact, they are not true bulbs but corms. Here, the base of the stem is used to store food, as is also the case with the gladiolus, which is regarded (in the broad sense) as a bulb. In the genus Iris can be found true bulbs, as well as rhizomes, but a rhizome is actually a creeping stem swollen to enable foods to be stored. Many begonias are considered tuberous, the tuber being an underground branch modified for storage and capable of producing buds and roots. These are not true bulbs but, to the world at large, bulbs, corms, rhizomes, and tubers all fall under the umbrella term bulb.

The diversity of color, flower form, size, habitat, and desirable growing conditions of bulbous plants rivals all other forms of vegetation. The flowers of certain Crocus species just manage to peep above the ground, while the towering shoots of Dahlia imperialis often will reach more than 16 feet in one season of growth.

Bulbs are found all over the world. Nomocharis is found above 12,000 feet in southwestern Sichuan Province, China; Hyacinthoides non-scripta (English bluebell) in the wooded areas and glades of Great Britain; Watsonia at the southern tip of Africa. Camassia quamash is at home in the wet meadows of the Pacific Northwest. The principal areas of the world, however, that are the common natural habitats of a high percentage of these plants are the Mediterranean; South Africa; Western Asia, especially Turkey and Iran; Central Asia and Afghanistan; the area around the Black Sea and the Caucasus; and the Pacific coasts of North and South America. Fewer bulbous genera are indigenous to Japan, tropical and North Africa, Great Britain, and eastern North America.