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Spring Bulbs

Dundee Fact Sheets

Spring Bulbs                                               Print This Sheet

Tulips

Most bulbs that bloom in the spring are native to areas that have either lengthy cold or dry spells. The bulbs spend 1/2 to 3/4 of their lives in underground dormancy during those periods of adverse weather. They have a stored bank of energy (starch) that is then quickly spent during the growth and flowering when moisture and rising temperatures occur.

The term “bulb” is applied loosely to many plants that live their lives in the fashion mentioned above. Technically, true bulbs are such flowers as tulips, daffodils, lilies, and hyacinth. A bulb is primarily made up of modified leaves containing stored food. If you slice a tulip bulb in half, you will see a miniature plant inside. Crocus are commonly called bulbs, too, but are really corms, which are modified stems used to store food. A new corm grows on top of the old one each year. Other modified storage stems are called rhizomes which grow horizontally slightly below the soil surface. Iris would be an example of a rhizome.

When planning your bulb area, keep heights, color, and bloom sequence in mind. In a tulip bed, for example, plant early bloomers toward the rear of the viewing area so you don’t have to look past dying foliage to see other late-flowering varieties. If you have specific color combinations in mind, be sure their bloom times correspond. Plant the bulbs in drifts rather than regimented rows and use a clump of each variety or color rather than creating a confetti of many colors. The smaller the bloom and/or the lighter the color, the more bulbs you need to make an impact.

Most bulbs need at least 1/2 day sun to perform well. However, if the shade is caused by deciduous trees, plant early to mid-season flowering bulbs. They will flower before the trees leaf out to shade the area.

Late September-October is the best time to plant spring-flowering bulbs. Although they do need time to develop roots before the ground freezes, don’t plant them so early in the fall that they might prematurely sprout. Tulips, in particular, can wait until late fall. Even planting into November generally is successful if you mulch the area heavily to postpone freezing. Bulbs demand well-drained soil and will rot if the soil is consistently waterlogged. If you have heavy clay, mix peat moss with the existing soil to a depth of 12” to improve drainage.

A general rule of thumb is to plant the bulbs 2-3 times deeper than the bulb is tall. This would mean about 8” deep for tulips, daffodils, and hyacinth, and about 3”-4” deep for most smaller bulbs. Specific instructions on planting depth are usually listed on each variety’s packaging. Use bone meal, superphosphate, or bulb fertilizer when planting to help root development. Mix these products into the soil well; don’t just spoon into the bottom of the hole. Keep spacing requirements in mind but don’t plant in precise rows. An irregular pattern will look much more natural. Depending on rainfall, water the bulbs about every 10 days until the ground freezes. Mulching late in the fall is recommended as a defense against an open, unusually cold winter.

After the bulbs appear in the spring, lightly fertilize with a complete bulb fertilizer. After blooming, the flower stem should be cut down, but the foliage must be allowed to mature and die down on its own. If you cut the foliage away before it has browned, the bulb will not be able to store food for next year’s flowering. Other plants, such as annuals, ground covers, or daylilies may be planted to hide the bulbs’ ripening foliage.

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