growing hardy bulbs

Ohio State University Extension Fact Sheet HYG-1237-98

By Jane C. Martin, Extension Agent, Horticulture, Franklin County

Hardy bulbs provide some of the earliest bloom in spring gardens. Growing and using them successfully requires a knowledge of life cycle, cultural requirements, and use. "Hardy" refers to their ability to withstand low winter temperatures and bloom year after year.

A true bulb is defined as a modified, underground stem, usually surrounded by scalelike, modified leaves, and containing stored food for the shoots enclosed within. The scales are held together by a hardened stem tissue, known as the basal plate (at the base of the bulb). Tulip, daffodil, hyacinth and lilies are examples of true bulbs. Crocus, thought by many to be a bulb, is actually a corm. This is a mass of fleshy tissue with a bud on the top surface. This tissue disintegrates as the stored food is used to produce roots and shoots. A new corm forms on top of the old one's remains. Bulbs and corms are living structures and require careful handling even while in a dormant state.

In general, hardy bulbs produce foliage and blooms in spring. They are in a dormant (resting) state over the summer months. Low temperatures are required to break dormancy so growth may resume in fall and early winter.

Good quality bulbs produce good bloom. Usually the larger the bulb, the better it will bloom. Beware of "bargain" bulbs that are often too small to bloom the first season. Bulbs should be firm, heavy and in good condition. The tunic (skin) should be smooth, of good color and free from injury. The basal plate must be intact.

Fall Planting
Bulbs can be obtained from many sources in the fall. Planting can occur from mid-August until the soil freezes. Daffodils, however, are best planted in September or early October because they require a longer period for root development. In the event that bulbs obtained through a mail order source arrive at an inconvenient time for planting, they should be stored in a cool and well-ventilated area.

Choose a planting site in full sun, but with protection from the hottest midday summer sun. Planting under or near large deciduous trees that cast filtered shade works well. Plants in full sun will bloom earlier than those in partial shade. A few plants that withstand partial shade include daffodils; Triumph, Parrot, and Fosterana tulips; some hardy lilies; some Crocus; Siberian squill (Scilla); checkered lily (Fritillaria); and some windflowers (Anemone).

Soil of a medium sandy-loam texture is ideal because it provides good aeration and drainage. Bulbs must not be planted in areas that do not drain well, or they will perform poorly or rot. If soil is a heavy clay, mix it with one-third to one-half organic material such as peat moss, compost, or aged bark. Raised beds also provide good drainage. Soil pH should be between 6.0 and 7.0.

Work soil 12 inches deep; loose soil below the bulb is important for good root development. Incorporate three pounds of a complete fertilizer (such as a 5-10-10 ) per 100 square feet as you are preparing the soil.

Recommended planting depths are given to the bottom of the bulb. For hyacinths, plant six inches deep; tulips, six inches or deeper; and daffodils, six to eight inches deep. Smaller bulbs in these groups and the minor bulbs are planted shallower. Large bulbs should be spaced four to six inches apart; small bulbs one to two inches. For a greater effect, plant in clumps or irregular masses rather than singly.

Once planted, replace half the depth of soil, then water. Finish covering with soil and water again. If fall weather is dry, water as needed to promote good root development. Mulch may be placed over newly planted areas once the soil has frozen to a depth of one to two inches. This keeps soil frozen and prevents alternate freezing and thawing, which may cause the soil to heave and injure newly planted bulbs.

Mulch can be placed over bulbs planted very late in the season to extend the root development period. The mulch can also be used to keep prepared soil from freezing. This method can be used for bulbs, such as hardy lilies, that cannot be obtained until very late in the season. After planting and as soon as soil has frozen to a depth of one to two inches, replace mulch.

Some bulbs are bothered by rodents, particularly squirrels, chipmunks, and mice. They dig and feed on (or store) tulip, Crocus, Chionodoxa and lily. Daffodils and hyacinths are not bothered. If rodents are a problem, and only a few bulbs are to be planted, consider enclosing them in hardware cloth boxes (use 1/2 inch mesh), or lay a sheet of hardware cloth over the planted area before replacing soil. Bulbs may also be dipped in Ropel®, a taste repellent, before planting to repel rodents.

In spring, rabbits feed on tulip and lily foliage. Chicken-wire enclosures or some of the taste repellents work fairly well.

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