Forcing Flowering Bulbs
This is my site Written by Geoff on November 1, 2002 – 7:05 pm

Winter, even for those of us that enjoy its beauty, can become rather drab for the home gardener. Although growing houseplants helps, they somehow start to lose their excitement after a while. This is when coaxing spring bulbs to flower indoors in the dead of winter is especially welcome. Bulbs can add color, aroma, and excitement to a home like nothing else. One look at a container of Katie Heath daffodils warms the heart and reminds us that spring is just around the corner. 

Getting bulbs to bloom indoors ahead of schedule is called forcing. Forcing is a process by which plants are stimulated to bloom other than at their normal time. Many spring bulbs can be forced indoors with only a little effort on our part. 

The first step is to select those varieties you wish to force. You will want to select the largest, healthiest bulbs for most flowers. Forced tulips do not bloom quite as well as garden planted tulips because they require a long rooting period but are still better than nothing. 

Some of the easiest varieties to force according to Nancy Anderson, a North Carolina Cooperative Extension Service Agriculture Agent, working as the Urban Horticulture Agent in Cumberland County are: 

  1. Narcissus – Barrett Browning, Bridal Crown, Dutch Master, Ice Follies, Paperwhites, Golden Harvest, Spell Binder, Salome, Pink Charm, Flower Record, Louis Armstrong, Unsurpassable, Tete-a-Tete, Jenny, Barrett Browning, Cheerfulness.
  2. Large-flowering crocus – Pickwick, Rembrance, Flower Record, Perter Pan, Purpurea Grandiflora.
  3. Hyacinth – Amethyst, Blue Jacket, Jan Bros, L’Innocence, Pink Pearl, Delft Blue, Hollyhock, Anna Marie, Violet Pearl, Gypsy Queen, Carnegie.
  4. Muscari – Blue Spike, Early Giant.
  5. Tulip -Apricot Beauty, Bing Crosby, Edith Eddy, Mirjorma, Yokohama, Jingle Bells, Attila, White Dream, Princess Victoria, White Swallow, Estella Rijnveld.

A listing of other suitable bulbs for forcing can be viewed at The Dirt Gardener’s website

Bulbs can be grown in any type of container. The roots are not long so the pot need not be deep. The pot size is important. It should be just large enough to hold all the bulbs without allowing them to touch each other or the sides of the pot. Choose a pot that is at least twice as tall as the bulbs. 

Since bulbs require porous soil and perfect drainage, a mixture of equal parts peat moss, potting soil, sand and vermiculite or perlite works well. Mix thoroughly and moisten with enough water to a damp consistency. Add one teaspoon of 5-10-5 dry slow release fertilizer to every quart of soil mix to give the bulbs an extra boost after flowering. Special bulb fiber may be used in place of potting soil. If you use fiber, place a one inch layer of soil or sand in the bottom of the pot first. Place a few pieces of broken pots or pebbles over the drainage holes, to prevent the soil from running out initially or clogging later. 

Fill the pot with your potting mixture so that each bulb top is even with the top edge of the container. Sprinkle soil around the bulbs until only the shoulders are showing. Plant several bulbs in a container for best display. They should be placed close together, but should not touch each other or the pot. Water the soil and keep it moist. 

Now your bulbs must be “chilled”, this is a period required for most bulbs to develop a strong root system. Begin 15-16 weeks before you want your bulbs to bloom. You need an area where bulbs can be stored at a cold temperature. A cool garage, unheated basement, or even an old refrigerator will do. Beware though that bulbs often do not mix with fruits in enclosed spaces because of the ethylene gas they give off as they ripen. Ethylene gas exposure can cause partial or incomplete flower abortion, retard growth, cause growth abnormalities such as excessive leafiness, shorten the lifespan of cut flowers, and inhibit development of flower buds. 

Place the pots in the area you selected for chilling. Ideally, temperatures should be 35-48 degrees Fahrenheit. If necessary, set boxes, pots or black garbage bags over your potted bulbs to keep them dark during the cooling period. Turning the pots every day or so keeps the flower stems straight and strong. In a week or two, the stems will elongate and the buds will become plump. 

When the stems are about 2 inches, tall, move the pot to a warm sunny spot to stimulate bloom. Move the pots to a bright, sunny window in the house, where temperatures are near 65 degrees once the foliage and buds are well developed. 

As the flowers begin to open, take the plants out of direct sunlight to prolong the bloom. During flowering, keep the plants in as cool an area as possible to encourage longer blooming. Keep the soil evenly moist and keep out of direct heat or drafts. 

After flowering, cut off the flower stems and place the pots in direct sunlight, keeping the foliage growing until it begins to die back. Hardy bulbs such as hyacinths and tulips cannot be forced again and should be discarded. You can try to plant them outdoors but it may take them a year or two to rebloom. 

Hyacinth, crocus and paperwhite narcissus, can be forced in water. You will have to anchor these bulbs to the bottom with small stones or use special forcing glasses. The glass is short and somewhat hourglass shaped. Keep the vase cool and dark for 3 to 6 weeks or until their roots have developed and the shoots appear. Bring the vase to a bright area where the bulb will flower as with conventional forcing methods. Bulbs that have been forced in water should be discarded after flowering. 

Forced bulbs can bring a little of Spring into your home even during the darkest Winter months. With very little work you can brighten up your home. Containers of forced bulbs also make welcome gifts, particularly during the holiday season.

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Modified: March 7, 2009 at 7:07 pm UTC

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