The true definition of a bulb can be a bit tricky. A bulb is technically any plant that stores nutrient reserves underground in some part of its anatomy. True bulbs, corms, tubers, tuberous roots, and rhizomes are usually all lumped into the category of 'bulb.'

Although they have differences, they are all basically underground reproductive structures that are capable of creating a whole new plant. Bulbs and bulb-like plants are usually perennials. Many bulbs prefer cold climates, but some, such as bamboo, prefer warm climates.

True bulbs have visible storage rings when cut in half. True bulbs can be sub-divided into tunicate bulbs and imbricate bulbs. Tunicate bulbs have a paper-like cover that protects the nutrient storage area. Imbricate bulbs lack this protective cover. Examples of tunicate bulbs are tulips, hyacinths, and daffodils. Lilies are an example of an imbricate bulb.

Corms are defined as an engorged stem base that serves to store nutrients. Corms have a basal plate from where the roots develop at the bottom on the corm. They also have a papery cover (tunic) like tunicate bulbs. Examples of corms are crocuses, gladiolas, and tuberous begonias.

Tubers are similar to corms but they do not have a papery covering or a basal plate. The roots develop out of small buds located around the tuber. Examples of tubers are anemones, caladiums, and oxalis. Potatoes, sweet potatoes, and the plant know in Mexico and Central America as “Yuca” are other examples of tubers. Yuca goes by the names “Manioc” and “Cassava” in other parts of the world.

Tuberous Roots actually store nutrients in their roots rather than in a swollen stem. Dahlias and tuberous-rooted begonia are considered tuberous roots.

Rhizomes tend to grow underground horizontally. These horizontal growths can pop out of the soil and form new plants. For this reason, many varieties of rhizomes are very invasive. Be careful when choosing plants that grow with rhizomes and where you plant them. Examples of rhizomes are lily-of-the-valleys, bamboos, and grasses.


Small, yet superior in strength, this Dutch perennial planting tool is the master at dividing perennials, lifting weeds and planting bulbs.

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