How to Force Garden Bulbs Indoors

Select one of three ways to force your bulbs: Grow them over water in forcing jars, or grow in potting soil or in gravel. The container dictates the planting method. Hyacinth forcing jars, found at nursery supply stores and online, are hourglass-shaped containers that allow you to grow various bulb types. Fill the bottom part of the vase with water for the roots, and then set the bulb on top; the shape of the container prevents the bulb from falling into the water. When growing bulbs in a pot, choose a container that is twice as deep as the size of the bulb. This means using a much smaller container for crocus than amaryllis. Make sure the container has ample drainage holes.

Do you enjoy the uplifting show of spring bulbs every year? If so, get a jump on the season and "force" bulbs to light up your indoor garden this fall and winter. Forcing refers to tricking bulbs to bloom out of season indoors by providing them with favorable conditions for growing. Plant bulbs, such as paper white narcissus and amaryllis, indoors now, and you can impress your friends and family with stunning, often fragrant indoor blooms in the months ahead. If you time things right, you can even enjoy these living masterpieces during the holidays.

September and early October, when bulbs are plentiful at the nursery and via mail order, is the perfect time to select them for forcing. Follow these tips to create an indoor flower paradise this autumn and winter.

Select Bulbs Carefully

Not all bulbs bloom well indoors. Knowing the best types for forcing, and how long they take to bloom after planting, will help ensure you have a successful growing experience. Here are good indoor bulb choices, including bloom times:

Large bulbs create big blooms. So, select the largest bulbs you can find and examine each for quality prior to buying. Choose bulbs that are firm; those with soft areas are likely to rot.

If you are unable to plant bulbs immediately after buying them, store them properly until planting time. Place amaryllis and paper white bulbs in a mesh or paper bag, and then store in a cool, dry, dark location. All other bulbs should be placed in a paper bag and put in the refrigerator. Avoid storing fruit (particularly apples) in the refrigerator at the same time, as ripening fruit releases ethylene gas that can cause bulbs to deteriorate or not flower.¹

Choose A Planting Method

Plant Bulbs

Place water-forced bulbs tip-end up, positioned with the bottom of the bulb 1/8 to 1/4 of an inch above the surface of the water. Roots will reach into the water.² Hyacinth, amaryllis and narcissus respond well to this method of forcing.

For other bulb types, it is best to force using gravel or potting soil. Plant bulbs about an inch apart, tip-end up, leaving 1/2 to 2/3 of the bulb exposed. If you cover the entire bulb, it may rot. After planting, water until the soil or planting medium is moist but not soggy.

Chill To Initiate Blooming

Place water-forced bulbs tip-end up, positioned with the bottom of the bulb 1/8 to 1/4 of an inch above the surface of the water. Roots will reach into the water.² Hyacinth, amaryllis and narcissus respond well to this method of forcing.

For other bulb types, it is best to force using gravel or potting soil. Plant bulbs about an inch apart, tip-end up, leaving 1/2 to 2/3 of the bulb exposed. If you cover the entire bulb, it may rot. After planting, water until the soil or planting medium is moist but not soggy.

Chill To Initiate Blooming

Except for amaryllis and paper white narcissus, bulbs require a period of chilling after planting in order to initiate blooming. Place the planted bulbs in a location with temperatures of 35 to 55 degrees Fahrenheit. Good locations include a root cellar, unheated garage, attic, shed or, if space allows, a refrigerator.³ If temperatures are cold enough, you can also chill the bulbs outdoors. Just make sure the soil or planting medium doesn't become overly moist.

Plant roots form and stems lengthen during this cooling period, which generally ranges from 10 to 15 weeks. If the bulbs were chilled by the bulb company prior to selling (refer to the packaging), the cooling period will be shorter. Consult the chart above for chilling time periods. Subtract any pre-chilling time, including any time spent in a refrigerator prior to planting.

During the chilling period, check on the bulbs periodically, and water when the top inch of soil or gravel becomes dry or when the water level in the jar is more than 1/2 an inch below the bottom of the bulb.

Transition Bulbs To Blooming

Remove bulbs from their cooling locations when they show a thick mass of roots in the forcing jar, or when they have 2 to 4 inches of stem growth and are well rooted in the soil. Move them to a dim, warmer (about 65 degrees Fahrenheit) inside location to initiate further growth and greening. After a week, move the bulbs to a brighter area. In two to four weeks, buds should form; soon after, the plant will flower.³

Forcing Without Chilling

Paper white narcissus and amaryllis are the easiest bulbs to force because they require no chilling. They bloom quickly inside and are great for succession planting — planting at intervals so you can enjoy indoor blooms throughout the fall and winter months. Time things just right and you will see these plants flower for Thanksgiving, Christmas, New Years and Valentine's Day.

Maintenance

To prolong blooms once they appear, keep plants out of direct sunlight and away from drafts and heating vents. For potted bulbs, continue to maintain a moist but not soggy soil environment; for water-grown bulbs, replace water to just below the bottom of the bulb every three days.

To prolong blooms once they appear, keep plants out of direct sunlight and away from drafts and heating vents. For potted bulbs, continue to maintain a moist but not soggy soil environment; for water-grown bulbs, replace water to just below the bottom of the bulb every three days.

Generally, no fertilizing is required with forced bulbs, because once the bulbs are finished blooming, they aren't likely to re-bloom the following year. It is sometimes possible to get bulbs to rebloom, however. This is easiest with those bulbs that don't require chiling, such as paperwhite narcissus and amaryllis.

If you wish to try your luck at saving the bulbs for next season, fertilize the plant after it finishes blooming and while the foliage is still green. Mix If you wish to try your luck at saving the bulbs for next season, fertilize the plant after it finishes blooming and while the foliage is still green.  Mix Pennington UltraGreen All Purpose Plant Food 10-10-10 into the soil as directed. . Continue watering the plant until the foliage dies back. Once the foliage has browned, let the soil dry out, and then remove the bulb and store it in a cool, dry place until next fall when you can start the forcing process once again.into the soil as directed, and then apply a 1/4-inch layer of earthworm castings to the surface of the soil. Continue watering the plant until the foliage dies back. Once the foliage has browned, let the soil dry out, and then remove the bulb and store it in a cool, dry place until next fall when you can start the forcing process once again.

Conclusion

Forcing bulbs indoors in fall and winter is quite easy when you follow a few simple steps. By choosing healthy bulbs, chilling them when necessary, and taking proper care of the resulting plants, you'll enjoy an early spring in your indoor garden.

Lilly Miller is a registered trademark of Central Garden & Pet Company. Pennington is a registered trademark of Pennington Seed, Inc.

Resources:

1. Ann Joy and Brian Hudelson, "Forcing Bulbs," Master Gardener, University of Wisconsin—Extension, March 9, 2012.

2. B. Rosie Lerner, "Forcing Bulbs for Indoor Bloom," Purdue University Cooperative Extension Service, July 2005.

3. George Graine, "Fooling Mother Nature: Forcing Flower Bulbs for Indoor Bloom," Virginia Cooperative Extension, 2014.