Fall Planted Bulbs for Spring Color
Dick Christensen
Colorado State University Extension Master Gardener in Larimer County
September 26, 2009
If you crave color in early spring after a long winter, fall's the time to dig in and plant bulbs. Along Colorado’s Front Range, some of the most commonly grown bulbs are tulips, crocus, hyacinths, muscari (grape hyacinths), snowdrops, Dutch irises, blue squill, glory-of-the-snow, daffodils and narcissi. Bulbs are easy to grow, requiring little attention. They tolerate both sun and partial shade. Spring-flowering bulbs add color to home landscapes earlier than most annuals and perennials. Many bulbs will bloom and multiply for years without a great deal of care.
Choose the largest bulbs of any variety, because there is a direct correlation between bulb and flower size. Avoid moldy, dry or damaged bulbs. Most bulbs do best when planted in September and October. Planting in early fall encourages root growth and earlier spring flowering. Bulbs planted after October may not have time to root adequately before the soil freezes and may not flower the first spring.
Cluster bulbs in flower beds, but also consider planting around trees and in borders. If the bulbs are to remain in a location for more than one year, they will need adequate sunlight to regenerate strong bulbs. Avoid southern exposures close to a foundation, as the reflected warmth can force bulbs to leaf out early and result in injury from freezing temperatures.
Dig beds to recommended depths; planting depths are measured in relation to the size of bulbs. As a general rule, the depth fro
m the soil surface to the top of the bulb is four times the height of the bulb. Bulbs should rest firmly in the soil, without any air space under the bulb. Plant yourr bulbs with the growing tip up. Apply fertilizer and soil amendments at this planting level. For fertilizer to be effective, it must be present in the vicinity of the roots. The flower bud and the food necessary to produce the flower are already present inside a fresh bulb.
Fertilizer promotes larger bulbs and improves the following year’s flower growth. When planting bulbs, mix phosphorus with the soil at a rate of one-half pound of 0-46-0 (super phosphate) per 100 square feet. If your soil is heavy and high in clay, mix it with some type of organic matter (peat moss or well-decomposed compost) to improve the texture of the soil. Amended soil offers less resistance to the bulb’s shoot as it emerges, and provides better aeration and drainage for root growth.
Space bulbs as recommended, then return the soil to the hole and water thoroughly. After the ground freezes, cover the bed with three inches of mulch to prevent freeze and thaw cycles that can break roots and damage bulbs. Mulch can be removed in April before the shoots emerge or left in place if shoots can emerge easily. Remove flowers as soon as they wither, since seed production diverts leaf-generated food that otherwise would be used to produce more vigorous bulbs. Apply nitrogen at the rate of one-quarter pound per 100 square feet before the foliage withers. After flowering, allow foliage to brown completely before removing it, as the leaves help the bulb store energy for next year’s blooms.
Fall bulbs can be planted with a master design or with total abandon. Solid blocks of single colors can be seen more easily from a distance than mixtures of colors and combinations of flower varieties. However, many gardeners plant bulbs with no plan or organized scheme. With attention to peak bloom time of specific varieties, either method can offer successive waves of welcome spring beauty.
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