What, Why, and How: Planting Fall Bulbs

What, Why, and How: Planting Fall Bulbs

After summer's scorching heat, autumn's cooler temps signal it's time to plant spring-blooming bulbs. They may not offer instant gratification, but with minimal effort, fall-planted bulbs will provide vibrant post-winter blooms well worth the wait. 

Going Underground—Life Cycle of Fall Bulbs

Spring-blooming bulbs have a unique growth cycle. They establish roots in the fall, spend winter underground, sprout and bloom in the spring and then go dormant in early summer.

Because most hardy fall-planted bulbs, including tulips, crocus, muscari, hyacinths and alliums, originate from climates with cold winters, they require chilling out for 10 to 13 weeks in temperatures below 40 degrees to bloom properly in the spring. This dormant period allows fall bulbs to establish a deep robust root system before sprouting foliage and flowers. The ground will become consistently cold over the winter to offer the bulbs plenty of the chill time they'll need to ready themselves for a burst of spring blooms. 

The dormancy begins as the weather grows colder and the days grow shorter. Once planted, bulbs start producing roots that absorb water and nutrients from the soil. While the soil insulates and protects the bulbs from frost damage, the cold temperature triggers a biochemical response that stimulates flower formation and root growth. The bulb's natural internal timer then begins counting down until it's time for its spring bloom.

In the garden planting flower bulbsIn the garden planting flower bulbs

When to Plant Fall Bulbs For Each Growing Zone

Gardeners in regions with cold winters (zones 4 to 7) can begin planting spring-flowering bulbs as soon as the ground cools and when evening temperatures average 40 to 50 degrees. As a rule of thumb, planting should start at least 6 to 8 weeks before the ground freezes, but not too early or they'll sprout and may suffer frostbite. (Consult this frost date calculator.)

In northern cooler regions, September and October are good planting months. Southern gardeners can plant bulbs a little later in October and November. But if the ground is still workable enough in winter to dig a deep hole, you can plant tulip bulbs as long as you can get them into the soil—often as late as January.

Even in zones 8-10, warmer climates not typically considered suitable for growing most tulips, gardeners can grow single late tulips such as the heat-tolerant Darwin Hybrid World Peace, whose long stems and 5-inch magenta and gold-edged petals make dazzling cut flowers. The Dordogne tulip will also survive in warmer growing zones, setting the garden aglow with its long, oblong, vibrant pink and orange-hued blooms.

Step-By-Step Guide to Planting Fall Bulbs

Choose a Sunny Disposition

Choose a location with full sun (6 to 8 hours of sun) or part sun (4 to 6 hours of sun) per day. 

Prepare the Soil and Give Bulbs a Drink

Bulbs like loose, well-draining soil. Select an area with well-draining soil, as they may rot if the soil is wet for an extended period. Prepare the bed by removing weeds, loosening the soil and applying rich organic matter or compost. Place the bulbs, cover them with soil, and gently press them to eliminate air pockets. After planting, top-dress the bed with a balanced, all purpose fertilizer such as Burpee 4-4-4 Granular Plant Food or Burpee Rose and Bloom 4-6-4 fertilizer, then give bulbs a generous drink of water to settle the soil and encourage root growth. Avoid placing fertilizer into the planting hole, as it can burn the bulbs. Mark where you planted them so you can locate the bulbs in spring!

Measure For Planting Depth and Spacing

The rule of thumb for most bulbs is to plant them three times their height and space them apart three times their width. Plant bulbs with the pointy side facing upward and the flat side down. When spacing, measure from the center of one plant to the center of the next, planting large bulbs 3 to 6 inches apart and smaller ones about 1 to 2 inches apart.

Consider the Layout

For a less choreographed, more naturalistic appearance, consider scrapping formal neat rows and instead plant bulbs in loose, irregular clusters of 12 or more large bulbs and as many as 50 smaller ones. Intermingle 5 to 7 different bulb varieties to meander in free-flowing drifts. When planting en masse, dig out a planting area large enough to place 7 to 12 bulbs, with the distance between each bulb varying between one to three inches. After planting those bulbs, dig another hole about one or two feet away and repeat the process. It's also fun to mimic nature by tossing bunches of bulbs randomly onto the ground and then planting them 4 to 6 inches deep wherever they land.

A monochromatic palette of one variety and color for small spaces can create maximum impact and make the area appear larger.

Give Bulbs Some Cover

If there won't be much snow on the ground or if temperatures will drop into the single digits after planting, cover bulbs with 2 to 3 inches of mulch to insulate them from frigid weather, protect them from injury, and keep nutrient-hogging weeds at bay that can attract pests.

hyacinth in the gardenhyacinth in the garden
Planting Hyacithn Bulbs

Easiest Fall Bulbs to Grow

Novice gardeners can start with easy-to-grow bulbs such as tulips, daffodils, crocus, hyacinths, muscari and snowdrops. For a reliable beginner tulip, try the Backpacker with its double purple peony-like flowers that last about three weeks in the vase without dropping their petals.

Succession Bulb Planting: How to Layer Bulbs for Continuous Blooms

Layering bulbs will produce a colorful succession of blooms throughout the spring season. For continuous blooms, select bulb varieties that blossom at different times: early, mid, and late blooms. As one set of bulbs blooms and begins to die back, new bulbs will burst forth with fresh flowers.

Lasagna Method of Succession Planting

The "lasagna method" of planting is just as it sounds—but instead of pasta, cheese, and sauce, it's three layers of bulbs within the soil:

•           The deepest layer for large late blooms

•           Mid-layer for mid blooms

•           The top layer for the smallest early blooms

Follow the bulb labels for specific instructions, but give them plenty of room to grow by planting them three times their height deep and three times their width apart. Add a layer of soil at least 2 inches thick above each bulb layer before starting the next layer. Continue this process for the third top layer, then water the whole lasagna deeply.  

Planting tulips, hyacinths, daffodils, gladiolus, allium and iris will produce a succession of colors and textures. Because of their many varieties, some tulips and daffodils will fall under all three bloom-time periods. Consider early bulbs, including mascari, daffodils and some tulips like the deep purple Continental Triumph or soft purple Candy Prince; the bright white mid-spring Carnegie hyacinth contrasting with multi-colored Candy Apple Delight tulips; some late spring-blooming Dutch iris along with Blushing Lady tulips.

Planting Bulbs With Perennials and Grasses

Another way to mix and match is to imitate the bulbs' native habitats by planting smaller perennials like peonies and ornamental grasses over larger bulbs. For intermittent bursts of color, add the bulbs to existing perennial flower beds. Early spring blooms will bring life and color to the beds, and later, as the bulbs go dormant, the grasses and perennials will help conceal the bulb's foliage.

Burpee Bulb ToolBurpee Bulb Tool

Supplies for Planting Bulbs

One of the best garden tools is your hands; others can make bulb planting even easier. Gardeners can dig fresh beds for planting en masse or create holes and place bulbs in the soil one by one with a bulb planter. A pointed dibbler is another helpful tool that makes good-sized holes for small bulbs. 

As you go about your end-of-season garden cleaning and sprucing up, take the opportunity to jump-start your flower garden with easy-to-grow fall bulbs that will burst with a pageant of color come spring. When you order Burpee's top-quality flower bulbs online, they arrive directly from their farms just in time for your zone's planting period.

April 30, 2024
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