Caring for Flower Bulbs

Caring for Flower Bulbs
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Caring for Flower Bulbs

Different Types of Bulbs and How to Plant and Care for Them


The word "Bulb" is often used incorrectly to refer to any geophyte. Bulbs are very specific nutrient storage organs that allow a certain group of flowering plants to perennialize and brave harsh conditions. Bulbs are formed at the base of the stem from layers of modified leaves that swell with stored nutrients. Roots grow from the bottom and the stem will shoot from the top. Popular bulbous plants are onions, narcissus, amayrillis, tulips, and garlic.


Corms are vertical plant stem nutrient storage organs similar in function to tubers, but their uniform shape and vertical orientation make them look more like bulbs. The difference between corms and bulbs is that a corm is made of one solid starchy section of stem instead of multiple layers of modified leaf material. A few examples of popular garden plants that produce corms are crocus, freesia, gladiolus, and banana.


Tubers are very similar to corms. They are solid nutrient storage organs that are made up of one solid piece of starchy plant material. The main difference is that tubers, unlike corms grow horizontal to the ground. Tubers can form on either roots or stems. Dahlia and Sweet Potato both form root tubers, and the plant just grows the tuber as part of its root system. Stem tubers are a little more complicated.

Stem Tubers: Rhizomes and Stolons

Rhizomes are spreading stems that grow horizontal to the ground often called "creeping root stalks". Rhizomes are the main stem of the plant. Nutrient-storing tubers will form along the rhizome as the plant reaches further out. Ginger, asparagus, and some varieties of iris are examples of plants that have rhizome tubers.

Stolons are also spreading stems, but the they are not the main stem of the plant. They reach out and, at the node of a stolon, tubers and new plants with vertical stems form. Stolons have two primary functions, finding light and reproduction. Strawberries and grasses, like some varieties of sedge, have stolons. Many plants that use stolons also produce rhizomes.

Storing, Planting and Caring for Your Flower Bulbs, Tubers, and Corms

Store your geophytes over winter to save you lot of money. You could just leave those rare and expensive bulbs in the ground and hope they come back next year, but it would be a lot safer to dig them up and keep them out of harm's way. Tropicals like caladiums, amaryllis, tender dahlia tubers, begonias, and callas all need to be taken up in the fall.

  • First dig your bulbs or tubers our of the ground. Be very careful not to damage them--it's best to dig them up by hand. Do this just after the first frost, or just before if severe weather is expected.
  • Move your plants to an airy place to dry out a little for about a week.
  • Cut off tops (the parts of the plant that would normally be above the ground) and clean off excess soil.
  • Store in clearly-labeled mesh bags, crate or boxes. Plastic bags trap moisture that may cause rotting.
  • Keep in a cool, dry place, away from frost and heat. If possible pack in slightly moist peat.
  • Check monthly--they should never dry to the point of shriveling.

Most bulbs can be planted again as soon as the ground warms up. Our flower bulbs will come with an information sheet providing all of the important planting information. For instance, many bulbs, corms, and tubers can go in the ground towards mid-spring, but caladiums don't need to be planted until mid to late April in most hardiness zones.

Once they are in the ground, geophytes are really easy to maintain. Use a well-draining, rich planting medium. For most, keep the soil moist, but not wet. Make sure you always get as much information about the plants you buy to make sure they don't have any specific, unique needs. Bulbs, tubers, and corms all work really well in containers, and some make really interesting house plants.

Quick Bulb Planting Guide

Be sure to verify your growing zone aligns with the zones in which these bulbs will thrive.

Item Planting Time Flowering Time Depth to Plant in Inches Sun/Shade
Allium Spring or Fall  Late spring, early summer  2X Diam. of the bulb  Full sun
Amaryllis 4-6 weeks before booms are desired Spring, unless forced 1/3 of bulb above ground Houseplant
Anemone Fall  Early spring          2-3   Sun or light shade
Butterfly Amaryllis 4-6 weeks before booms are desired Spring, unless forced  Base of bulb below soil line  Houseplant
Calla Lilly (Zantedeschia) Late spring                 Early to mid summer 3              Sun
Colchium Aug-Sept   Sept-Oct 3-4  Sun or light shade
Crocus, Autumn  Sept-Dec Fall  2-3 Sun or light shade
Crocus, Spring       Sept-Dec Early spring 2-3  Sun or light shade
Cyclamen Late summer, early fall  Fall  Top of corm level with soil  Shade
Eranthis Early fall  Early spring  2 Shade
Eremurus Foxtail Lilly Sept-Dec  June 4-6   Sun
Freesia Early spring Summer Sun
Fritillaria Imperialis Fall   Early spring   4-6   Sun
Fritillaria Meleagris     Fall   Spring 3-4  Sun
Galanthus Fall  Early spring 2-3    Shade
Gladiolus, Hardy Fall or early spring Spring 2-4 Full sun
Hermodactylus Fall   Early spring 3-4     Sun
Hyacinth   Fall Early spring 4-6 Sun or light shade
Ipheion Fall  Early spring 3-4 Sun or light shade
Iris, Bulbous Aug-Sept Early spring  2-3 Sun
Leucojum Summer Snowflake Fall April  4-6   Sun or light shade
Lily Fall or spring   Early spring 4-6  Sun or light shade
Lily of The Valley Convallaria Fall or spring May-June Light shade
Lycoris Hardy Amaryllis                   Mid-summer to fall  Late summer, early fall 2-4  Sun or light shade
Muscari Late summer, early fall  Early spring  3 Sun or light shade
Narcissus, Daffodils  Sept-Oct  Apr-May 5-6   Sun or light shade
Oxalis Fall Spring 2    Full sun
Ranunculus Spring Early spring 1.5 Full sun
Scillia Hispanica Fall Spring 2-3 Light shade
Scilllia Siberica                                        Fall   Mar-Apr 3 Sun or light shade
Tulip Hybrid                               Fall Spring 6-8 Sun
Tulip Species Fall  Spring 2-3 Sun
Zephyranthes                      Spring Mid-summer 1-2  Shade