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Extension > Garden > SULIS > Maintenance > Sustainable Herbaceous Plant Maintenance > Bulbs, Rhizomes, Corms and Tubers

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Bulbs, Rhizomes, Corms and Tubers

Iris Spring blooming bulbs are a welcomed sight after a long winter. Bulbs are available in a wide variety of sizes, colors, and forms and can provide a great deal of color and textural interest in small or large areas. They require minimal effort on the part of the gardener and landscape professional, and they add a great deal of beauty to the landscape.

There are several types of bulbs and bulb-like structures: true bulbs, which are divided into two groups - scaly bulbs like Asiatic lilies (Lilium asiatic) and tunicate bulbs like tulips (Tulipa species); tubers like dahlias (Dahlia hybrids) have leathery skin and feature "eyes" that are buds; rhizomes such as iris (Iris hybrids) are really underground stems and grow just below or on the soil surface. Crocus (Crocus vernus) and gladiolus (Gladiolus hybrids) are examples of corms, a compressed stem that contains food and has a bud on top. Bulbs and bulb-like structures share something very important in common: they serve as storage structure for food that provides the energy for the plant to grow, bloom and complete its lifecycle each year. The foliage is responsible for photosynthesis, creating energy for the plant and storing it in the bulb.

Bulbs may be hardy (spring- and early summer-flowering) or tender (summer-flowering). Hardy bulbs are planted in the fall, generally before the first frost, and can survive (and indeed require for sprouting) the cold winter months. Most hardy bulbs, such as tulips and daffodils, can be left in the ground to flower year after year. Examples of hardy bulbs are tulips, daffodils (Narcissus species and hybrids), iris, crocus, and lilies. Here are some recommended websites for information about hardy bulbs:

Tender bulbs including dahlias, begonias (Begonia tuberosa) and gladiolus are planted in the spring for summer bloom. They cannot survive cold winter temperatures and must be dug each fall and stored for the winter indoors in a cool, dry place. Tender bulbs are planted in the spring after the soil has warmed. For facts about how to care for and store tender bulbs, visit Storing Tender Bulbs and Bulb-like Structures from University of Minnesota Extension.

For more on proper plant selection based on site and plant characteristics, see Plant Elements of Design plant selection database.

For information about specific tender bulbs, visit these sites:

There are many websites, books and publications about bulbs. If you are looking for an all-inclusive website about bulbs, visit the Netherlands Bulb Information Centre website. It is written in English, and provides everything you need to know about selecting bulbs, caring for them, seasonal blooming, purchasing, etc. Visit the International Bulb Society website for communication with other bulb enthusiasts and access to articles and member newsletters (You must be a member to access various areas of the site).

Click on any of the following headings and link to chapters that explain care and maintenance of herbaceous plants.

Dividing Plants
Dividing Rhizomes
Starting Plants from Seed
Collecting and Saving Seed
Self-Sowing Plants
Transplanting Seedlings, Cuttings and Divided Plants

Staking, Supporting and Training Plants
Methods of Supporting Plants
Materials & Structures
Training to Improve Plant Health (FUTURE)
Training Plants for Ornamental Purposes (FUTURE)

Cutting Back Plants
Pruning for Plant Form
Pruning to Prevent Disease (FUTURE)
Deadheading and Pinching Back (FUTURE)

Mulching & Watering
Why Use Mulch?
Application of Mulch
Mulching for Weed Control
Mulching for Winter Protection
Mulching for Moisture Control
Organic Mulches
Synthetic Mulches
Watering Your Landscape
How to Determine the Frequency and Rate of Watering
Water Quality and its Effect on Plants

Nutrition, Fertilizers, and Compost
The Basics of Plant Nutrition and Fertilizers
Soils (FUTURE)
Compost (FUTURE)
Fertilizer: the Do's and Don'ts
Organic Fertilizers (FUTURE)
Inorganic Fertilizers (FUTURE)
Salt Tolerant Plants

Weed Management
Weed Identification and Lifecycles
Cultural Management Methods for Weed Control
Pruning for Weed Control (FUTURE)
Understanding Labels (FUTURE)
Alternatives to Chemical Herbicides (FUTURE)

Diseases and Insects
Integrated Pest Management (FUTURE)


American Daffodil Society,

American Hemerocallis Society,

American Iris Society,

International Bulb Society,

Meyer, Mary H., list of bulbs, 2000 core course packet, HORT 1011, University of Minnesota.

Netherlands Bulb Information Center,

Ohio State University Extension "Herbaceous Ornamentals: Perennials, Annuals and Bulbs", Master Gardener manual, Jack Kerrigan and Margaret Nagel.

University of Minnesota Libraries, Bell Museum, "Tulips", Barbara Schulman. 2002

University of Minnesota Extension, "Spring Bulb Basics", Yard & Garden News, April 1, 2000, vol. 2, no. 4, Deborah L. Brown.

University of Minnesota Extension, "Storing Tender Bulbs and Bulb-like Structures", FS-1117-GO, Mary H. Meyer, 1998.

University of Minnesota Extension, "Growing Dahlias", FS-1115-GO, Paul E. Read and Deborah L. Brown, 1993.

University of Minnesota Extension, "Growing Daylilies", FS-1106-GO, Mary H. Meyer, 1999.

University of Minnesota Extension, "Iris for Northern Gardens", FS-1113-GO, Deborah L. Brown, 1998.

University of Minnesota Extension, "Selecting Lilies for Your Garden, FS-1112-GO, Anne M. Hanchek and Jane E. Bolla, 1997.

University of Nebraska, "Growing Gladiolus", G87-852-A, Amy J. Greving. Revised March 1992.

University of Rhode Island, "Forcing Bulbs", Greenshare, Sharon Bale, University of Kentucky.

University of Rhode Island, "Iris Culture", Greenshare, Leslie Diebec, Ohio State University Extension. 2000.

University of Wisconsin Cooperative Extension, "Cannas, Dahlias, Gladiolus & Tuberous Begonias: Digging, Storing", Info Source, #453, Sharon L. Morrisey, 1996.

University of Wisconsin Extension, "Iris: Dividing Iris", Info Source, #449, Sharon L. Morrisey, 1996.

University of Wisconsin Extension, "Bulbs: Care of Tulips / Daffodils after Blooms", Info Source, #455, Sharon L. Morrisey, 1996.

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