The symphony of early-spring color produced by fall-planted bulbs and corms is one of nature’s most magical gifts to the gardener. After a long winter’s rest, these odd, brown, papery, onion-looking things push their green shoots sunward through the soil, to announce a new season of re-birth, renewal and growth. If you want to enjoy the magic of fall-planted bulbs, you need to invest a little time and energy now. Following a few recommended practices will help ensure a burst of color in your garden in the early spring.

Spring-flowering bulbs need time to establish their roots before the soil freezes, and they need a period of cold temperatures to prepare them for spring blooming. That’s why late September to mid-October is the best time for planting bulbs along the Front Range. Planting after October can result in inconsistent flower production.

Whenever possible, choose planting sites that allow you to view the colorful blossoms from the comfort of a window, while showing off the flowers to those passing by. Bulbs make a great companion planted in shrub borders, mixed perennial beds and among evergreen ground covers. Some gardeners like to plant a solid bed of one color for maximum impact. Others experiment by mixing varieties and colors of early-, middle- and late-bloomers to produce a dynamic symphony of color over several weeks during springtime.

Bulbs will be happy in full sun or partial shade, but if you intend to leave the bulbs in place for more than one year, remember the importance of sunlight for the plants to store energy and regenerate themselves after blooming. A southern exposure, especially one near a heat-conducting structure like a sidewalk, driveway or foundation, can cause early growth emergence and result in freeze damage.

Take time to improve the soil in your planting site. Properly prepared soil will encourage root growth through good drainage and aeration, and the improved soil texture will offer less resistance to new shoots as they emerge in the spring. Dig the bed down to the proper depth for the type and size bulbs being planted. Apply a high-phosphorus fertilizer and organic material such as peat moss or well-decomposed compost at the same level. Mix these components into the soil while deepening the bed another three to four inches in order to allow the roots to take advantage of the nutrients.

Once you’ve decided what varieties to plant, select bulbs that are firm, large and unblemished to produce the best blooms. Bulbs are available now at garden centers and nurseries. Hard-to-find varieties are often available through mail-order companies.

Try to achieve a “natural” configuration by scattering a handful of bulbs and planting them where they land. Some gardeners choose to plant groups of three, five or seven bulbs in individual holes, while others prefer planting a large number at one time in a single large space. Whichever method you choose, avoid planting in straight lines.

Plant bulbs with their growing tips up, at a depth that is approximately four times the overall height of the bulb. For small bulbs, like crocus or grape hyacinth, that means a depth of four to five inches. For larger bulbs, like tulips, six to eight inches is a good rule of thumb. Be sure the rounded base of the bulb is firmly set into the bottom of the planting bed. Replace the soil over the bulbs and water them gently but thoroughly.

After the ground freezes, your bulbs will benefit from a 3-inch layer of organic mulch to prevent damage that can occur when soil temperatures fluctuate in the early spring. In April, or when the emerging foliage reaches two inches above the soil, the mulch should be removed. More details can be found from Colorado State University Cooperative Extension Fact Sheet 7.214, Mulches for Home Grounds.

After the foliage emerges and before blooms appear, judicious application of a balanced all-purpose fertilizer will encourage growth and better blooming. Continue to water the plants as needed. After the blooming period ends, allow the foliage to remain in place to convert sunlight into food for the bulb as it goes dormant. Some gardeners prefer to replace the bulbs with annuals for the summer season. Others plant annuals among the bulbs to help disguise the withering plant tops. In either case, do not remove the bulb tops until they are dead.

For more information about fall-planted bulbs, contact your county Cooperative Extension office, and ask for Fact Sheet 7.410, Fall-Planted Bulbs and Corms.

The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.

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This page updated:  September 28, 2006