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Not everything that grows underground is a root. Bulbs grow foliage above the ground, and, when the weather is dry, help preserve life so they can grow again the following spring.

CONTRIBUTED PHOTO BY LEE ROUSE

Many gardeners take an "out of sight, out of mind" approach when dealing with the part of the plant that's underground.

Most people call the part of the plant below ground the root, but that's incorrect.

Certain plants have stems, leaves and scales that grow underground as well. Bulbs, corms, rhizomes are underground organs that can be difficult to tell apart. So, let’s shed some light on this underground world.

Bulbs are considered shortened, compressed stems that are surrounded by fleshy scale or modified leaves. An excellent example of bulbs would be onion, garlic, shallots, daffodils and tulips. Take an onion, for instance. Cut it in half, and you can see at the basal section of the onion is an area that is the compressed stem with modified leaves surrounding it.

Bulbs are more often found in climates that tend to have moist springs, which trigger the bulb to grow foliage above the ground, and summers that tend to be very dry, allowing everything above the soil to die. This helps to preserve life underground within the bulb so it can grow again the following spring.

Gardeners are able to grow many bulbs very well in south Louisiana. The problem is keeping them alive in the ground year after year. Oftentimes, our winters are far too wet. This can lead to the bulb rotting over the winter and not returning the following spring.

Corms, on the other hand, are similar to bulbs but lack the fleshy scales or modified leaves. The gladiolus and crocus are prime examples of corms. True bulbs tend to grow and increase in dimension from seasons to season while corms replace themselves completely every season. These new tubers sit on the older, desiccated ones and will be the producer of foliage and flower the following season.

Another group of plants that depend on the underground storage organs are tubers. This group can be easily distinguished from bulbs and corms because they produce multiple shoots and more often than not they are irregularly shaped. Whereas bulbs and corms will typically only have one growing point, tubers have many. Potatoes and cyclamen are great examples of tubers. If you've ever left a potato in the pantry too long, multiple eyes or buds will begin to sprout. These are the beginnings of new plants.

Rhizomes, which are closely related to the tubers, are a group of plants characterized by swollen stems that grow horizontally. These underground stems are highly effective storage components. Plants such as irises, cannas and gingers fall into the rhizomes arena.

Got a question?

Email gardennews@agcenter.lsu.edu.