What light bulbs go off when you hear the word 'bulb'?


Halifax Media Group

Brent and Becky’s Bulbs is a catalog company, “Garden Bulbs for the South” is a book by Scott Ogden and “Bulbs Are Great — If You Choose Wisely” is a chapter in Hamilton Mason’s “Your Garden in the South.” What do they have in common beyond the obvious? All deal not only with bulbs, but also with tubers, tuberous roots, corms and rhizomes.

But while the word “bulb” is simply shorthand for advanced gardeners, it's a hazy catchall for average folks who think all plants with swollen subterranean structures are bulbs.

A true bulb is actually an underground stem enveloped by fleshy, starch-storing leaves that provide energy for the embryonic plant that will eventually emerge. The bulb’s bottom — its basal plate — serves as the foundation for the entire plant and also generates roots. In addition, the basal plate produces offsets called “bulblets.” Among true bulb plants for Central Florida are Easter lily, garden amaryllis, blood lily and crinums such as “Queen Emma.”

Tubers are also modified underground stems, but they lack basal plates, produce roots from a larger area and frequently form numerous growing points called “eyes.” Familiar tubers include potatoes, sweet potatoes and caladiums.

Plenty of other plants have tuberous roots that, unlike tubers, are true roots that form at the base of a stem. But compared to typical roots, tuberous roots do double duty by serving as major nutrient-storage systems for plants such as daylily and dahlia.

Returning to basal plates and modified stems brings us to corms, which differ from bulbs in that each is a single mass, not composed of scales. Roots are generated by a cormous plant’s basal plate, as are small growth buds called cormels. The corm most familiar to local gardeners is gladiolus.

Finally — sort of — there are rhizomes, which are fleshy, often elongated stems that grow mostly underground. Roots develop along a rhizome’s underside, while eyes, or growth buds, form at various points along its upper surface. Many kinds of plants including iris, false blue ginger, calla, lady palm and bamboo are rhizomatous.

If you’re wondering about stolons, they’re similar to rhizomes but grow along the soil’s surface, rooting here and there and forming new plants at those points. St. Augustine grasses spread by stolons.

Charles Reynolds, a Winter Haven resident, has an associate's degree in horticulture and is a member of the Garden Writers' Association of America.

Last modified: November 22, 2013
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