Bulbs (Units 65-68) (Includes Bulbs, Corms, Tubers, and Rhizomes)

1. Major vs. Minor Bulbs

Major bulbs are Hyacinthus (Hyacinths), Narcissus (Daffodils), and Tulipa (Tulips).

These terms are not based on bulb size but more on popularity.

Minor bulbs is used for everything that is not the three above.

The largest bulbs are the Allium giganteum and related plants.

The giant onion bulbs are the size of a large orange or a grapefruit.

2. Planting Bulbs

Most books and bulb packages list the recommended planting depth.

A general rule is to plant a bulb at a depth that is twice the diameter of the bulb.

Bulbs planted in heavier soils should be planted shallower than the recommended depth.

3. New Bulbs May Flower Later Than Those Already in the Ground

Newly purchased bulbs often flower a week or two later than bulbs of the same

cultivar that are already in the ground. This occurs because the summers are

cooler in Holland and England where most commercial bulbs are produced. These

new bulbs mature later and thus flower later.

4. Mulching Bulbs

Mulches do protect tender bulbs, but deep mulch is a problem if not removed very early

in the spring. Tulips will come up through heavy mulch, but the stems will fall over.

5. Bulbs Not Planted in the Fall

If bulbs are forgotten in the house or garage, they should be planted as soon as

possible, even into December. Bulbs that don't receive the proper cold period

will have unpredictable results. They may flower at the ground or not flower at all.

6. Why Tulips Stay Short Stemmed

It could be the characteristic of that cultivar.

It could be unusually high spring temperatures that keep the plant from developing


It could be poor soil, lack or moisture, or soil where root development is difficult.

7. Why Tulips and Other Bulbs Fail to Flower

Bulbs need to be a certain size before they will have the stored energy to produce

flowers. Be sure to keep the leaves on until they yellow and die down, so they can

build up the bulb for next year. Lack of adequate light, water, or nutrients can

also produce leaves and no flowers.

Bulbs will not flower if there is not a long enough cold treatment (4-6 weeks at

40 degrees Fahrenheit or below; but don’t freeze).

Lack of adequate water while growing in the spring, can cause flowers to abort.

During storage, high temperatures, or exposure to ethylene gas from ripening fruit,

can cause flowers to abort.

8. Useful Books

 *1. Bryan, John E. 2002 (rev. ed). Bulbs. Timber Press, 133 S.W. 2nd Ave., Ste. 450,

Portland OR 97204. 524 pages. Encyclopedic Treatment of bulbs, corms, tubers, and rhizomes.

SB/425/.B74/2002 ($89.95)

* 2. Heath, Brent, and Becky Heath. 2001 (rev. ed.). Daffodils for North American Gardens.

Bright Sky Press, New York, NY. 144 pages. Excellent photo guide arranged by Divisions.

SB/413/.D12/H43/2001 ($24.95)

* 3. Heath, Brent, and Becky Heath. 2001 (rev. ed.). Tulips for North American Gardens.

Bright Sky Press, New York, NY. 144 pages. Excellent photo guide arranged by Divisions.

SB/413/.T9/H45/2001 ($24.95)

 *4. Leeds, Rod. 2000. The Plantfinder’s Guide to Early Bulbs. Timber Press, Inc., 133 S.W. 2nd Ave.,

 Ste. 450, Portland OR 97204. 192 pages. Covers Crocus, Eranthis, Galanthus, etc.